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The characteristics of the fluvial geomorphic parameters and its formed dynamic analysis for the Seerteng Mountain, northern margin of the Hetao basin

WANG Ping, SONG Jinyue, FENG Shaoying, GAO Shoujie, MENG Xiangshuai, LIU Dongliang, DENG Xiaojuan, LI Qian, JIA Jia, HUA Xinsheng, SONG Wei, WANG Shengyang

Submitted date:2022-07-06,Pre-publication date:June 25, 2023

DOI: 10.19762/j.cnki.dizhixuebao.2023139

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Topography is formed by the complex interactions between tectonics and erosional surface processes, which is primarily mediated by tectonic activity and bedrock erodibility. The rock uplift by tectonics can be negligible in the ancient orogens for its tiny tectonic activity, then it is possible to study the contribution of rock erodibility to the landscape evolution. However, most recent results show that topography is mainly controlled by tectonics in the active orogens, and the reports of lithological control on landscape evolution are not involved. As the controlling fault for the Hetao Basin, the Seerteng mountain-front fault had been active since the Holocene, which resulted the M 6.4 and M 5.9 history earthquake in the 1979 and 1934. Previous studies show that the center section (such as the Wujiahe site) has stronger activity than its west and east sections. However, the researches of geomorphic parameters are less than other faults in the northern margin of Hetao Basin (such as the Langshan fault, Wulashan fault and Daqingshan fault), which will hinder to understand its deformation dynamics. Using the 30 m DEM, we extracted the Hypsometric integral of 33 subbasins in the Seerteng Mountain and normalized channel steepness, longitudinal profile and the Knickpoint of the corresponding streams. The HI values are clustered between 0.44 and 0.66 with the highest value at the Wujiahe town, indicating that the evolution stage of the Seerteng Mountain is the “Middle” stage. The transient and steady rivers are all distributed along the fault, which reveal that the rivers in the Seerteng mountain-front are developed during the transient state and then evolved to the steady state. By comparing the knickpoint and lithology, we find that the knickpoints are under-controlled by tectonic uplift and/or lithology. The channel steepness (Ksn) has a character of spatial difference. The Ksn near the Wujiahe town is the highest, and it gradually decreases to the east and west part, then it increases to the west part at the River S8. By analyzing the rock lithology, precipitation and tectonic, the channel steepness (Ksn) is controlled by the lithology, and its spatial distribution is in accord with the fault activity (vertical slip rates and offsets). The landscape of the Seerteng Mountain is the results of the tectonic uplift and rock lithology.
Application and development of numerical simulation in the study of fold-and-thrust belts in sedimentary basins

Yin Hongwei, Jia Dong, Wang Wei, Li Changsheng, Xu Wenqiao, Yang Gengxiong, He Wanhui

Submitted date:2023-02-24,Pre-publication date:June 06, 2023

DOI: 10.19762/j.cnki.dizhixuebao.2023136

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Numerical simulation is a method that uses computers to solve engineering, physical, and even natural problems by numerical calculation and graphical display. With the development of high-performance computing, numerical simulation has been widely used in structural deformation research of sedimentary basins and has achieved fruitful results. On the basis of reviewing the previous studies, four main numerical simulation methods are introduced: finite element method, finite difference method, boundary element method, and discrete element method. Then, the results of previous studies have been summarized to conclude the effects of several first-order parameters on the geometry and evolution of fold-and-thrust belts in basin deformation. This paper aims to provide a comprehensive understanding of numerical simulation and to guide future researchers to apply this method in basin deformation. At last, the limitation and developing direction have been discussed.
Chromium isotope systematics and its applications in chromite deposits

BAI Yang, SU Ben-Xun, XIAO Yan, SHI Ren-Deng, PAN Qi-Qi, YUAN Qing-Han, CUI Meng-Meng, WANG Jing

Submitted date:2022-10-31,Pre-publication date:May 22, 2023

DOI: 10.19762/j.cnki.dizhixuebao.2023132

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In recent years, chromium (Cr) isotope systematics have been widely used in tracing geological processes related to mantle partial melting, magma differentiation, and subduction fluid-related processes. This study summarizes the main advances in using Cr isotope geochemistry in chromite deposits in mafic-ultramafic rocks, including: ① Cr isotope compositions of chromite and coexisting silicates in the peridotite zone of the Stillwater complex and crust-mantle transition zone of the K?z?lda? ophiolite reveal that Cr isotopes had been significantly fractionated during formation of both stratiform and stratiform-like chromitite, which was mainly controlled by fractional crystallization and magma replenishment; ② Cr isotope compositions of the podiform chromitite from K?z?lda? ophiolite suggested that spinel in the mantle peridotites in the subduction zone is one of the mainly Cr sources in podiform chromitite, and the subduction zone fluids may also directly participate in mineralized formation; ③ Diffusion-driven inter-mineral Cr isotope fractionation in ophiolite and layered intrusion can not only be used to estimate cooling time of magmas, but also reveal critical medium role of hydrous fluids in chemical exchange between minerals.
Differential uplift of granitic pluton in the Basu region of the eastern Bangong-Nujiang suture zone: Evidences from zircon and apatite fission tracks

ZHU Xunzhang, Liu Dongliang, LI Haibing, PAN Jiawei, ZHAO Zhongbao, WANG Ping, LI Chao, LIU Fucai, ZHENG Yong, MI Guilong

Submitted date:2022-08-09,Pre-publication date:April 26, 2023

DOI: 10.19762/j.cnki.dizhixuebao.2023127

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The Bangong-Nujiang New Tethys Ocean suture zone is an important tectonic boundary, separating the Qiangtang block and the Lhasa block in the Qinghai-Tibet Plateau. This suture zone is one of the important windows to deciphering the growth history of the Qinghai-Tibet Plateau. This suture zone can be divided into three parts: the western (from Banggong Lake to Gaze), middle (from Anduo to Dongqiao) and eastern (from Dingqing to Nujiang) sections. Few studies were involved in the eastern section, which contains abundant structural evolution information of the Bangong-Nujiang suture zone. In this study, a vertical profile of granite near Guoqing village of Basu County is taken to study the tectonic uplift process by the fission track dating, including zircon fission track (ZFT) and apatite fission track (AFT) with laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). The zircon U-Pb ages center at ~180 Ma, indicating that its crystallization age is the Early Jurassic. The ages of ZFT and AFT are ~180-130 Ma and AFT are ~86-61Ma, respectively. The QTQt simulation showed that the upper NJ-01 sample of the profile had a fast erosion rate during ~130-60 Ma, the middle NJ-03 sample and NJ-04 sample had a slower erosion rate during ~130-40 Ma, and the lower NJ-06 sample maintained the slowest during rate since ~130 Ma. This differential uplift is caused by the earlier slab break-off in southward subduction than in the northward subduction, which induced the negative slope of the Age-Elevation Relation of ZFT and positive slope of the Age-Elevation Relation of AFT. Based on this and previous research results, the granites with age of 180 Ma in the Basu area are resulted by the northward subduction of the Bangong-Nujiang suture zone, the erosion uplift induced zircon fission track cooling age since ~180 Ma, and the erosion uplift generated apatite fission track cooling age during ~86-61 Ma.
Distribution and causes of Mid-Carboniferous dolomitization in South China

Song Yingfan, Wang Xiangdong, Li Ying, Shi Yukun, Hu Keyi, Huang Xing, Sheng Qingyi, Yao Le

Submitted date:2022-11-17,Pre-publication date:March 15, 2023

DOI: 10.19762/j.cnki.dizhixuebao.2023313

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Carboniferous is an important period in the geological history when the Hercynian Orogeny happened and the Late Paleozoic Ice Age (LPIA) reached its peak, which resulted in frequent fluctuations of eustatic sea level and dramatic changes in palaeoclimate and palaeoenvironment. At the Mid-Carboniferous boundary interval, a vast of shallow platform dolomitization occurs widely in South China. This paper summarizes the thickness and age of dolostones in three major carbonate platforms in South China, and further clarifies their temporal and spatial distribution. In terms of characteristics of global climate and environment in this interval, we propose that the maximum glaciation could be the cause of eustatic sea-level fall which resulted in the widespread dolomitization in South China. The different temporal distributions of dolostones among sedimentary basins in South China might be related to their independent developing history of basins and different diagenetic patterns. The dolomitization in the Middle-Lower Yangtze Carbonate Platform could be the Sabkha pattern and the seepage-reflux pattern in the early burial stage, therefore, forming relatively thin-bedded dolostone deposits. The thick-bedded dolostones in the Central-Southern Carbonate Platform and the Southwestern Carbonate Platform could be formed in the seepage-reflux pattern
Discovery and significance of micro scale new minerals in podiform chromitites

YAn Jinyu, Xiong Fahui, Xu Xiangzhen, Yang Jingsui

Submitted date:2022-05-17,Pre-publication date:January 01, 2023

DOI: 10.19762/j.cnki.dizhixuebao.2023107

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The earth""s microscopic minerals, even molecular and atomic minerals, play an important role in revealing the history of the earth""s development and the evolution of the mantle crust. As an important carrier of micro-geological action mechanism, micro scale minerals can solve the problem of migration and circulation of crust and mantle materials such as elements. In order to focus on this view, we need to turn our attention to one of the carriers of these micro-sized minerals: podiform chromitite. Podiform chromitites are the main source of chromium and rare mineral species in China. In recent years, with the application of experimental techniques such as single crystal diffractometer, micro-area and micro-diffraction and the progress of computer science and technology, many new achievements have been made in the mineralogical research of podiform chromitites. In particular, Deposits where micro scale minerals have been discovered include the Luobusa chromite deposit in Tibet, China, the Othrys deposit in central Greece, and the Loma Peguera deposit in the Dominican Republic. Thirteen micro scale minerals including luobusaite, linzhiite, naquite, zangboite, yarlongite, qusongite, titanium, qingsongite, badengzhuite, zhiqinite, wenjiite, kangjinlaite and jingsuite have been discovered in the Luobusa chromitite, and four micro scale minerals such as arsenotuekite, eliopoulosite, tsikourasite, grammatikopoulosite have been discovered in the Othrys ophiolite. They have been formally approved as new minerals by the Committee on New Minerals, Nomenclature and Classification of the International Mineralogical Society (IMA-CNMNC). The new minerals are named according to the place names of mineral discovery areas and their adjacent areas or scientists who have made outstanding contributions to geoscience research, and are mainly composed of transition elements (Fe, Cr, Ni, Mo, V, etc.), titanium silicide, carbide, nickel phosphide and natural elements. Through the study of the mineral chemical composition and crystal structure of these micro-nano minerals, and with the help of Focused Ion Beam (FIB) technology, we reflect the characteristics of micro minerals from BSE images, crystal structure images and other ways. Their discoveries greatly expand human understanding of the crystal structure and crystal chemistry of mantle minerals and provide a basis for further interpretation of the physical and chemical properties of the mantle. The reduction environment produced by these ultra-high pressure micro-nano minerals will provide new insights into the physical and chemical conditions and material composition of podiform chromite and even the deep mantle we have studied, and at the same time, the composition of micro minerals will also give a reasonable explanation for the study of crust-mantle material cycle.
Impact origin of diamond and prospecting for future mineral exploration

Li Zhaoli, Liu Fei, Zheng Yongchun, Yu Xiaoyan, Xiao Bingjian, Yang Jingsui

Submitted date:2022-10-11,Pre-publication date:December 15, 2022

DOI: 10.19762/j.cnki.dizhixuebao.2023106

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Opening of the Neo-Tethys Ocean in the Late Triassic? Sedimentary responses on the north Indian continental margin

Meng Zhongyu, Wang Jiangang, Li Weitong

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The Neo-Tethys recorded by the Indus-Yarlung-Zangbo suture zone in southern Tibet has been a vast ocean between Eurasian and Gondwanan continents during the Mesozoic and was closed in southern Tibet as a result of India-Eurasia collision in the Early Cenozoic. It is a common view that the Neo-Tethys Ocean was formed as a result of rifting of the Lhasa block from the eastern Gondwana. However, when the rifting had occurred remains controversial. Proposed timing for opening of the Neo-Tethys varies from Early Permian to Late Triassic. In this study, we carried out an integrated stratigraphic and sedimentological study on the Permian-Triassic strata deposited on the north Indian continental margin. Our data indicated that depositional environment kept stable since cessation of the glacial period in Early Permian. Notable change in sedimentary environment only occurred in the Late Triassic, from carbonate platform to terrigenous clastic shelf. Facies change was accompanied by increasing depositional rate, accelerating tectonic subsidence, provenance change, bimodal volcanism, and paleogeographic reconstruction. These changes clear revealed a regional extensional event, which was considered as responses to the opening of Neo-Tethys.
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Petrogenesis of the late Oligocene granites in Milin area, the eastern Gangdese arc

Wang Di, Zhang Zeming, Li Wentan

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Cenozoic granites are widely exposed in the Gangdese magmatic arc of the southern Tibetan Plateau. However, the origin of these granites remains controversial. We report geochronology and geochemistry study about the late Oligocene two-mica granites from the Milin area in the eastern Gangdese arc. Whole-rock chemical analyses show that these granites belong to medium-high potassium calc-alkaline series, weakly peraluminous. The samples are enriched in light rare earth elements and large ion lithophile elements such as Rb, Th and U, and depleted in heavy rare earth elements and high field strength elements such as Nb, Ta and Ti. All samples exhibit high Sr and low Y, with high Sr/Y ratio (37~85), and chemical affinity to adakites. The two-mica granites have the crystallization age of ~26.6 Ma. Zircon Hf isotopes show that these granites have low and positive εHf(t) values (+0.4 to +7.3). Taking previous data into account, we conclude that the late Oligocene granites from the Milin area were derived from partial melting of the Eocene arc-type magmatic rocks in the thickened lower crust, but with contribution of ancient crustal materials. The continental collision-induced crustal shortening and thickening resulted in the partial melting of the thickened lower crust, and formation of the widespread late Oligocene adakitic granites.
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Impact glasses in Chang"E-5 regolith

XIAO ZHIYONG, YAN PAN, WU YUNHUA

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Impact glass formed by cooling of impact melt and condensation of impact vapor is a common component in lunar regolith. Impact glass in lunar regolith records important information about the composition of lunar materials, regolith fortion process, and impact flux on the Moon. Regolith samples returned by the Apollo and Luna missions were developed on terrains that are older than 3.6 Gyr old, and their provenanaces are usually complexed and uncertain. Earlier investigations of lunar geology and geochemistry based on impact glasses in regolith usually contain ambiguity in the interpretation. The Chinese Chang’E-5 lunar spacecraft returned regolith samples from both the surface and subsurface in one of the youngest mare units on the Moon. The regolith samples have relatively homogeneous compositions, and basaltic clasts in the regolith exhibit similar characteristics that are consistent with being formed by a single episode of flooding basalts. Therefore, the Chang’E-5 regolith was mainly developed from the local mare units, and components delivered from the other geochemical units or lunar impactors are minor. From this perspective, the Chang’E-5 regolith is an ideal agent to study the physical and chemical mechanism of regolith formation based on impact glasses. In this work, we extract 153 glass particles (larger than 20 μm) from 500 mg of Chang’E-5 regolith. We investigate their detailed surface morphology, interior structures, and major and trace elements compositions. We show that the glass particles were formed from impact melt, and most of them were derived from the local mare materials. Intricate surface structures are observed on the surface of the glass particles, the correlated high-resolution morphology and composition analyses suggest that most of the microstructures were formed by local materials with low collisional speeds. This study proves that regolith formation on the Moon mainly occurs by low-speed collisions of local particles, while direct contributions by distal ejecta and lunar impactors are minor.
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The indicative significance of apatite geochemical characteristics on tin metallogenic capacity of granite—A case study of Xiaolonghe tin deposit in Tengchong-Lianghe tin belt, western Yunnan

Chen Xiaocui, Mao Kainan, Yang Wei, Yang Wu, Yan Jun, Li Peng, Jiang Hai

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Tin mineralization is extremely uneven distributed in the world, and is closely related to granitic magmatism, which attached considerable attention on the granite tin metallogenic capacity study. It is important to well constrain the magmatic source and accurately trace the magmatic evolution process for understanding the tin metallogenic capacity of granite. Apatite, as a common accessory mineral in granitoids, its chemical composition has a unique advantage in tracing the magmatic sources and diagenetic process of its host granite. In this study, apatite in situ chemical composition analysis of granite from the Xiaolonghe tin deposit in the Tengchong–Lianghe tin belt in western Yunnan Province was carried out. The results show that the granite from the Xiaolonghe tin deposit is of highly differentiated granite, and characteristic of A-type granite. The granite magma is mainly originated from the ancient continental crust. The granite, with rich F and certain Cl content, was formed in a relatively reductive environment. These characteristics of the Xiaolonghe granite indicate that it is conducive to the accumulation and migration of Sn in the granitic magmatic evolution process. Thus, the structure and chemical composition of apatite can well constrain the granite genesis, magmatic evolution, physical and chemical conditions of magma, which can effectively evaluate the tin metallogenic capacity of granite.
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Microoriganism fossils in cherts from the Wanlong Formation in southern Jilin Province

Zhang Dejun, Liu Pengju, Shang Xiaodong, Yang Ben

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The Tonian period marks one of the most critical time intervals in the evolutionary history of the early life and environment. It follows a golden age of cyanobacteria in the Mesoproterozoic and precedes a global biological collapse in the Cryogenian. The southern Jilin Province, situated on the northeastern margin of the North China Block, offers an excellent opportunity to study paleontology, biostratigraphy and paleoenvironment during the Tonian period. This region boasts complete sedimentary successions of strata, well-exposed outcrops, and the presence of various well-preserved microfossils within chert bands, nodules, and shales. In this study, we present an assemblage of microfossils discovered in cherts from the uppermost sediments of the Wanlong Formation in the Erdaojiang area of south Jilin Province. We have identified a total of nine species belonging to six genera, including filamentous cyanobacteria such as Siphonophycus robustum, S. typicum, S. kestron, S. solidum, spheroidal cyanobacteria such as Eoentophysalis belcherensis, Gloeodiniopsis lamellosa, Scissilisphaera bistratosa and incertae sedis species like Glenobotrydion majorinum, Globophycus rugosum. These newly documented microfossils provide valuable insights into the paleoenvironment of the Wanlong Formation and facilitate the regional correlations of biostratigraphy. Furthermore, the microbiota is predominantly composed of cyanobacteria filaments, particularly Siphonophycus mat, with horizontally oriented filaments typically exceeding 400 μm in length, indicating taphonomic characteristics of autochthonous or near-autochthonous preservation. The comprehensive analysis of the paleoenvironment suggests that the uppermost sediments of the Wanlong Formation in the Erdaojiang area of south Jilin Province represent a shallow, low intertidal or subtidal environment with a low sedimentation rate.
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Mid-Holocene sea-level fluctuation in the Fujian coastal area: evidence from ostracod records of Core NDQK5

JIA Baoyan, Peng Bo, WANG Jilong, YU Junjie, ZHOU Baochun, ZHAO Quanhong, LI Baohua, WANG Yaqiong

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The Quaternary deposits are widely distributed in the Fujian coastal area where is the ideal place to study the relative sea level changes since the late Pleistocene. Based on AMS 14C and optical stimulated luminescence (OSL) dating techniques, the high-resolution ostracod records from the Core NDQK5 obtained from Ningde of Fujian Province were used to reconstruct the relative sea level changes in this area during the mid-Holocene. Ostracods occurred at the depth interval of 4~17.1 m in Core NDQK 5 corresponds to about 8.2~6.9 cal. ka BP. Twenty-six marine ostracod species belonging to twenty-three genera are recovered from the core samples. On the basis of the relative abundance of main ostracod elements, three ostracod assemblages were identified. The ostracod assemblage A dominated by Bicornucythere bisanensis and Sinocytheridea impressa indicates a subtidal zone environment; the assemblage B with dominant species Sinocytheridea impressa and Neomonoceratina delicata represents the nearshore inner shelf; the assemblage C with the dominant species Sinocytheridea impressa and Loxoconcha ocellifera indicates the intertidal zone environment. Our ostracod data pointed out that a continuous sea level rise occurred in the Fujian coastal area since ~ 8.2 cal. ka BP, and the sea level reached the highstand during the period of 7.9 to 7.4 cal. ka BP; a fall in seal level existed in the period of 7.4~7.0 cal. ka BP, and then a minor sea level rise has been recognized. Hence, our results indicate that several minor fluctuations in sea level existed in the Fujian coastal area during the Holocene sea-level highstand period. Combined with the previous studies, we conclude that the sea level change in the Fujian coastal area was probably controlled by the meltwater from the ice sheet during 8.2~7 cal. ka BP; however, it was probably controlled by Glacio-hydro Isostatic Adjustment (GIA) effect after 7 cal. ka BP.
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Neoproterozoic sequence stratigraphy in the northwestern margin of the Tarim Basin and its regional correlation significance

Shen Weibing, Wang Yifeng, Wang Yangyang, Xie Hongzhe, Wang Xun, He Yuan

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The division and regional correlation of Neoproterozoic sequence in the Tarim Basin are helpful for the study of early environmental evolution and deep oil and gas exploration in the basin. Integrating results of previous studies with an analysis of the sedimentary characteristics of the Neoproterozoic successions in the Aksu area of the northwestern Tarim Basin, a detailed investigation on sequence filling pattern of this area and its regional significance of sequence correlation were carried out. Associated with the three-stage evolution of the rift basin, the Neoproterozoic successions of the northwestern margin of the Tarim Basin can be divided into three sedimentary sequences. During the syn-rifting stage at the early Cryogenian, Sq1, composing of glacial and shallow-water shelf deposits in the Dongqiaoenbrak Formation and the Muyangtan Formation, was formed and distributed in isolated small barrier-graben basins. During the rifting-to-depression transformation stage at the late Cryogenian-early Ediacaran period, Sq2 was formed. Due to enhanced connectivity of the rifting basin, it had larger distribution range and was composed of the Youermeinak Formation and Sugetbulak Formation, developing glacial, tidal and shallow water shelf deposits. During the depression stage at the late Ediacaran period, Sq3 was formed. It was composed of the Chigebulak Formation and developed carbonate platform deposits. According to the sedimentary-tectonic background and chronological stratigraphic framework of the Tarim Basin, the Neoproterozoic sequence filling pattern in the Aksu area of the northwestern basin, characterized by three stage, can be compared with the Kuruktag area of the northeastern basin and the Yecheng area of the southwestern basin, and the diamictites at the bottom of the Sq1 and Sq2 are correspond to the global Sturtian and Marinoan glaciation, respectively.
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Spatial-temporal distribution, resource potential and exploration progress of carbonatite-type rare earth deposits in central and southern AfricaTANG Wenlong¹⁾^,2⁾

Tang Wenlong

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As the most important metallogenic type of endogenetic rare earth deposits, the carbonate type rare earth deposits in central and southern Africa have superior geological metallogenic conditions and great resource potential. Combined with the spatio-temporal distribution characteristics of igneous carbonatite, this paper discussed and summarized the regional metallogenic regularity, resource potential and exploration progress of carbonatite-type rare earth deposits in central and southern Africa. Carbonate type rare earth deposits were divided into four metallogenic belts: Pilanesberg-Phalaborwa belt, which the metallogenic epoch were mainly concentrated in the Paleoproterozoic – Mesoproterozoic; Namaqualand-Bushmanland-Warmbad belt, which the metallogenic epoch were 40-80Ma; west margin of Namibia - Angola belt which could be further divided into two categories,one was the carbonate rare earth deposit influenced by the Parana- Etendeka hot spot, and the metallogenic age was 140~125Ma; the other was controlled by the Damara orogenesis, and the metallogenic age was 750~550Ma. The REE metallogenic belt of the East African Rift system could be further subdivided into three metallogenic subbelts: the southern part of the East African Rift system, the western branch of the East African Rift system and the eastern branch of the East African Rift system. The southern part of the East African Rift system subbelt ranged from Buhera, Zimbabwe to Malombe, Malawi, and the metallogenic age was mainly concentrated in 135-110Ma. The west branch of the East African Rift system subbelt extended from Chipala of Malawi through Ngualla of Tanzania, northward to Lake Albert, Uganda, whihch the metallogenic ages could be divided into three stages: 1100~1000Ma, 700~500Ma and 120~100Ma. The East branch of the East African Rift system subbelt extended fromWigu Hill in Tanzania northward to Afar triangle in Ethiopia, which the metallogenic age could be divided into two stages, 120~110Ma and 5~25Ma, respectively. The spatio-temporal distribution of each metallogenic belts, the metallogenic geological background of typical deposits, the characteristics of the deposits, and the metallogenic conditions were systematically summarized, and the resource potential of the metallogenic belt and the exploration progress in recent years were sorted and dissected. China's rare earth work in central and southern Africa started late. Although some progress has been made, it’s still necessary to accelerate the resource exploration and development activities.
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Geochemistry and Petrogenesis of Early Paleozoic alkaline rocks in the South Qinling Belts: research progress and prospects

LAI Shaocong, Yang Hang, Zhang Fangyi

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The South Qinling belt experienced large-scale and continuous alkaline magmatism during the Early Paleozoic, and the record of alkaline rocks provides a valuable geological vehicle for exploring the deep material composition, magmatic evolution, physicochemical environment and geodynamic evolution of the region. This article aims to provide a comprehensive understanding of the source area and evolution of early Paleozoic alkaline magmatism in the South Qinling Mountains, based on the team's recent work on the genesis of typical alkaline rocks in the region. The Early Palaeozoic alkaline rock types in the South Qinling belt mainly consist of a bimodal suite with a change in composition from basaltic to trachytic, and a small number of carbonatite coeval with alkaline silicate rocks (amphibole pyroxenites and syenite). Petrographic, chronological and geochemical evidence suggests that these alkaline rocks share the same mantle source area, with the mafic rocks recording partial melting of the mantle in the South Qinling Mountains, where the metasomatic agent was mainly silicate melt. The trachyte/syenite and carbonatites are all derived from magmatic differentiation of the initial mafic component, with the trachyte/syenite being controlled by segregation and crystallization of mainly feldspar and clinopyroxene. Hydrothermal processes are mainly concentrated in the Zhuxi-Zhushan area in the eastern part of the Northern Daba Mountains and the south-western margin of the Wudang region, where hydrothermal metasomatism has led to the enrichment of rare earth elements in carbonatite. Geochronology and monazite Nd isotopic signatures suggest that the hydrothermal fluids may have originated from a reactivation event in the rock itself, and that the Late Triassic orogeny of the Qinling region may have contributed to this process.
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Spatiotemporal distribution, geological characteristics and metallogenic mechanism of indium (gallium, germanium, cadmium) associated deposits in China: Overview and expectation

Yi Zheng, Chun-Li Guo, Deng-Hong Wang, Ting Zhao, Yan Wang

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Indium (In) is an important strategic mineral in short supply in the 21st century, which is of great significance to national stability, development and improvement of international competitiveness. China has the most abundant indium resources in the world, but no independent deposit of indium has been discovered. There are 57 associated indium deposits, which have the potential of cadmium (Cd), gallium (Ga) and germanium (Ge). Based on a detailed review of the regional distribution, genetic types, formation ages, indium-bearing minerals, independent indium minerals and enrichment regularity of 57 associated indium deposits, we summarized the research status and development direction of indium mineralization. The associated indium deposits are highly concentrated in the eastern part of the central Asian orogenic belt and South China. There are seven genetic types, including skarn type, magma-hydrothermal type, marine volcanic-rock type, continental volcanic-rock type, superimposed (composite/modified) type, porphyry type, and metamorphosed type. Indium is mainly hosted in sphalerite without exception, and is recycled as by-product.At present, 19 indium independent minerals have been discovered, only 5 indium independent minerals were found in China. Roquesite (CuInS2) is the most common indium independent mineral that has been found in our country，other indium independent minerals such as natural indium and hydroxindium（InSb）are reported to occur only in specific associated indium deposits. At present, the Skarn associated indium deposits, which are located in the southwestern margin of the Yangtze block, get more attention than other deposits. The research of the other six deposit types scattered throughout other areas were studied less. This is a limit not only to understand the indium enrichment mechanism, but also to find out new indium resources. Therefore, it is very important to enhance the research of representative associated indium deposits and build the more detailed database.
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Characteristics of melt inclusions of Miocene adakitic porphyries in the southern margin of Lhasa terrane

Zhao Xiaoyan, Yang Zhusen, Dong Yanrui, Liu Chang

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Miocene adakite porphyries are widely distributed in the southern margin of Lhasa terrane, but there are obvious differences in the composition of ore-forming elements and the scale of mineralization. In order to better understand the constraints of different mineralization of Miocene porphyries in the southern margin of Lhasa terrane, this paper selects the ore-bearing porphyries of Jiama Cu deposit and Bangpu Mo deposit, to carry out TIMA scanning and electron probe studies of single melt inclusions in quartz phenocrysts of the different porphyries. The results show that the melt inclusions of Jiama and Bangpu are mainly crystalline whose crystalline minerals mainly include quartz, albite, orthoclase, plagioclase and mica. There is a significant negative correlation between SiO2 and K2O in the melt inclusions of Jiama and Bangpu, which all belong to the?high-K calc-alkaline to shoshonite series. The Jiama ore bearing porphyry has lower Cl (0-0.03 wt%) and higher H2O (1.12-4.35 wt%) contents compared to Bangpu porphyry. Research has shown that the injection of ultrapotassium magma and strong crystallization differentiation of potassium feldspar play an important role in the formation of porphyry deposits of collisional environment. In addition, the content of volatile matter (including H2O, Cl, etc.) plays a significant role in the differnent metallogenensis.
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Chronology and Genesis of the Tong'an granite aplite in Yifeng, Jiangxi Province

ZENG Runling, ZHANG Jingruo, HE Ling, OUYANG Yongpeng, WEI Jin, MENG Delei

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The Ganfang duplex granite formed in Yanshan period is the most important ore-hosting rock in Yifeng Li-Nb-Ta rare metals ore field. The aplite, the product of the late stage of magmatic evolution in the Ganfang complex granite, is closely related to the mineralization of the aplite-vein type rare metals in the Yifeng area. However, little research has been done on these rocks. In this paper, petrographic, cassiterite U-Pb chronological and whole-rock geochemical analysis have been carried out on the Tong'an granite aplite in Tong'an mining area, south of Ganfang granite. Cassiterite LA-ICP-MS U-Pb dating results show that the aplite formed at about 138 Ma. According to the results of geochemical analysis, it is characterized by high Al2O3, P2O5, CaO and alkali (Na2O+K2O) contents, and lack of Mg, Fe and Ti. The granite aplite has high A/CNK ratio (vary from 1.71 to 1.88) and low σ value (between 1.40 to 1.72), belonging to high potassium calc-alkaline rocks with highly peraluminous. In terms of trace and rare earth elements, the Tong'an granite aplite is enriched in Rb, U, Ta, Pb, P, Hf elements and depleted in Ba, Th, Sr, Ti elements, as well as highly lack of rare earth elements. These characteristics indicate that the Tong'an granite aplite belongs to highly fractionated S-type granites. It is derived from the partial melting of metamorphic sandstone from the shallow crust, formed in the tectonic transition background from intracontinental co-collision to post-collision while the paleo-Pacific plate subducted to Eurasia plate. In the process of formation, it experienced high degree of fractional crystallization in early stage and magmatic-hydrothermal interaction in late stage. In addition, this paper believes that the early highly fractional crystallization plays an initial enrichment role in lithium mineralization, while the magmatic-hydrothermal interaction in the late evolution stage is the key to the high enrichment of lithium and the eventual mineralization.
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Ediacaran diamictites and glaciation in Northern China

liuyongqing, Kuang Hongwei, Chen Xiaoshuai, Wang Yuchong, Jiang Xiaojun, Xy Huan, Qi Kening, Peng Nan

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Glaical diamictites developed during the Ediacaran Period in more than a dozen continents worldwide. This is especially notable in several cratons and blocks in Northern China, where they can stretch for 3,000 km from east to west. However, the exact age and paleogeographic distribution of the Ediacaran glacial diamictites; their glacial scale, intensity, and depositional characteristics; and similarities and differences compared with those formed in the Cryogenian Earth have been controversial. As they are currently located within the Tethyan tectonic domain, the affinities of the cratons and blocks containing Ediacaran diamictites with Rodinia or Gondwana and their tectonic setting are still unclear. In this study, we focus on the Ediacaran diamictites either in the North China,Tarim Cratons and the intervening microblocks in Northern China. We systematically describe their spatial and temporal distribution, geological age, lithofacies, sedimentary features (with cap dolomite and detrital zircon provenances), and glaciated landscapes. Ediacaran diamictites from North America, South America, Northwest Africa, Arabia-Iran, and Northwest Australia were compared with those in Northern China. The study concludes that ice age events later than 580 Ma (Gaskiers) were widespread in Northern China and worldwide, the Ediacaran diamictites in Northern China were formed in 583-551 Ma, and the terrestrial and marine sedimentary facies such as subglacial, periglacial, and proglacial, can be identified. The widespread distribution of Ediacaran diamictites, cap dolostones, and intercontinental glaciated landscapes in China and the world, and the relationship between Ediacaran diamictites with the evolution of Rodinia and Gondwana, indicate that the Ediacaran diamictites were the product of intercontinental ice ages (glaciation). The study suggests that final breakup of the Rodinia led to the birth of the Proto-Tethys Ocean between the Pan Asia Continent Chains (PACC) to the north, and Western Gondwana (WG) to the south. The Proto-Tethys Ocean and arounding PACC, and WG were covered by continental glaciers after the Pan-African convergence events in the middle Ediacaran. Meanwhile, the ice sheets of PACC and WG moved toward the Proto-Tethys Ocean, and the glacial sediments transported by glaciers and ice-melted rivers accumulated in the PACC rift systems and WG continental margins. However, the zircon provenances of glacial deposits from the PACC and WG are dramatically different. In particular, the former has no record of the deformation, magmatism, and metamorphism events that occurred in the Pan-African. The results of this study provides insight into the global paleogeographic reconstruction and tectonic evolution of Ediacaran glaciation, the background environment of Ediacaran fauna and metazoans, and the Cambrian explosion.
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Discrete Element Numerical Simulation of fault development characteristics of Strike—slip Pull—apart Basin

LI Xin, HUANG Lei

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The development and evolution of strike—slip fault zone is closely related to the formation and evolution of pull—apart basin. The secondary faults and pull—apart basins developed under different overlapping ranges of the main faults have different scales and shapes. Previous studies have mostly used physical simulation to study the evolution process and fault development characteristics of strike slip pull—apart basins. There is a lack of analysis of fault deformation characteristics during the evolution of basins and the discussion on the law of fault evolution under different degrees of overlap of main faults. Based on the discrete element simulation software PFC2D, this paper simulates the development and plane evolution law of faults in the pull—apart basin under three conditions: underlapping, neutral and overlaping. The results show that the fault development of the pull—apart basin experienced a process that faults development from the ends of the strike—slip main faults to the internal releasing bend and then expend to the exterior ,and regardless of the degree of superposition of strike—slip main faults, the law is well reflected. In addition, the high degree of overlap between the fault development position and the stretching area indicates that the development law of the fault is of great significance to the migration of the depocenter of the pull—apart basin.
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Study on lithologic classification method based on lithologic index and 3D feature space

Zhang Qunjia, Wang Le, Liu Lei, Wang Yalei

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Remote sensing lithologic classification, especially the automatic identification of mafic-ultramafic rocks and granite, is of great significance for mineral exploration. Currently, the lithologic classification methods, which integrate visible light near-infrared (VNIR), short wave infrared (SWIR), and thermal infrared (TIR) images, are relatively lacking. In this study, the Advanced Spaceborne Emission and Reflection Radiometer (ASTER) data were employed for lithologic mapping in the Huitongshan, Beishan, Gansu Province, and Huangshan, East Tianshan, Xinjiang Province. The mafic-ultramafic rock index (MI), quartz-bearing rock index (QI), and the comprehensive ratio were established according to the reflection spectrum characteristics of rocks in the VNIR-SWIR region and the radiation characteristics in the TIR region. The lithology index and comprehensive ratio results were then used to build a three-dimensional feature space model. The specific lithology was classified and extracted according to the clustering characteristics of rocks in the feature space. The model was applied to the lithologic classification of Huitongshan in the Beishan of Gansu Province and Huangshan in the east Tianshan in Xinjiang, field observation confirms that the classification results are of high accuracy. The results showed that the proposed lithologic index and three-dimensional feature space model using VNIR-SWIR and TIR data could successfully extract target lithology with high precision and applicability, which has a good application prospect in western China.
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Morphological Characteristics of Diamonds Grown at HPHT Conditions and Implications to Natural Diamonds

Lu Zhiyun, Yang Jingsui, Lian Dongyang, Wu Weiwei, Yang Yu, Cao Chuqi, Cai Pengjie

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The formation conditions of natural diamonds, such as pressure, temperature, and the composition of crystallization medium, have long been a fundamental concern in geoscience. Recent advancements in high-temperature and high-pressure techniques, and the industrial production of synthetic diamonds, have enabled extensive investigation on the morphology of synthetic diamonds and their dependence on temperature, pressure, and composition. In this paper, we conduct a comparative morphological analysis of synthetic diamonds grown under different conditions and different types of natural diamonds. The paper provides a clearer understanding of the P-T parameters and mantle fluid composition related to the crystallization of natural diamonds.
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Characteristics of strike-slip faults and their oil-gas-controling effect in the Ordos Basin

He Faqi, Huang Lei, Zhang Ru, Zhang Wei, Wang Zhao

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The Ordos Basin is thought as a stable block and has few faults in its interior. In recent years,a large amount of small scale faults have been revealed in the interior of the Ordos basin using 3D seismic. The discoverychanges the thought for the structural characteristics of the basin and the exploration direction for the oil and gas. However, the geometry, kinematics characteristics and genetic mechanism of these faults are still unresolved, and the controlling factors for accumulation of oil and gas are still unclear. In this study, the characteristics of such strike-slip faults developed in different tectonic units of theOrdos basin were compared, and its effect on hydrocarbon were analyzed . Faults develops in the Ordos Basin, trending NEE, NW, N-S and E-W respectively. These faults have the common characteristics (such as subvertical dip angle, small slip distance and concealmen. All the faults show the nature of strike-slip characteristics. However, the dominant strike of faults in various regions of the basin is different: the northern is nearly E-W-trending, the southern is mainly NE-trending, the southwest is NW-trending and the fault strike in the interior of the basin is multi-direction. The formation and evolution of intra-basin faults are controlled by the tectonic stress field around the basin. The faults near the periphery of the basin formed in the similar stress field; and the stress strength is weak in the interior of the basin. Due to the layered structure style of faults in the Ordos basin, the upper and lower petroleum systems are independent. It is mainly fault-fracture clastic reservoirs in the Mesozoic and fault-karst carbonate reservoirs in the Lower Paleozoic. The faults and derived fractures assembly in the interior of the Ordos Basin compose special reservoir sweet spots.
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The Effect of Enhanced Basalt Weathering on Soil Heavy Metals

Tang Xiaowei), Liao Libing), Wang Lijuan), Liu Hao), Xie Xiuxin), Jiao Chennan)

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Enhanced basalt weathering can release heavy metals and accumulate in soil, while the weathering products of basalt have a certain passivating effect on soil heavy metals. Therefore, investigating the bioavailability of heavy metals in soil during enhanced basalt weathering process is of great significance for the practical application of enhanced-basalt weathering carbon sequestration technology. This study used Tessier method, SEM, EDS, and other characterization methods to study the effect of enhanced basalt weathering on soil heavy metals. The results showed that basalt weathering increased soil pH, making heavy metals in soil more easily passivated. Most of the Cr and the Ni leached from basalt were fixed in residual form by basalt weathering products and soil clay minerals, and only a small amount of Cr and Ni flowed out with the effluent, causing no soil pollution. The new minerals formed by Ca, Mg, and Fe ions released by basalt dissolution during weathering, as well as other basalt weathering products, can transform heavy metals in soil into stable forms, reducing their bioavailability and achieving the goal of remediating soil heavy metal pollution.
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Deep explanation model of the VMS-type deposit in the Ashele ore district

Meng guixiang, Deng zhen

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The Ashele copper deposit is the typical VMS-type Cu polymetallic deposit in northe-west of China. With the continuous deepening of exploration development of deposits, metallogenic (genetic) and exploration models of deposit have been continuously improved. Moreover, it has played a positive role in guiding prospecting and exploration of deep edges of deposits. We comb that effective geological exploration models on different scale deposit (body) structure models via studying exploration and prospecting models on metallogenic (genetic) models of the Ashele ore district from commonness to individuality, from the shallower to the deeper, simplicity to comprehensiveness. We propose "multi-channel volcanic chain" geological exploration model based on ore district scale, and discuss the construction of deep comprehensive exploration models of the VMS-type Cu metalogenic deposit in the Ashele ore district.
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Large-scale granite-related tungsten and tin mineralization in South China: Temporal and spatial distribution, metallogenic models and exploration implications

Ni Pei, Pan Junyi, Han Liang, Cui Jianming, Gao Yan, Fan Mingsen, Li Wensheng, Chi Zhe, Zhang Kaihan, Cheng Zhilin

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South China is the most important tungsten and tin metallogenic region in China. Centering on the large-scale granite-related tungsten and tin mineralization in South China, this paper preliminarily summarized their main types and temporal-spatial distribution characteristics based on a systemic review of the updated information of deposit geology and isotopic chronological data of more than 130 major deposits. The results show that the skarn and quartz-vein types are the most important tungsten mineralization styles in South China, while skarn type and cassiterite-sulfide are the most important tin mineralization styles. Granite-related tungsten and tin mineralization in South China show multiple-aged characteristic, but the major mineralization of both tungsten and tin is formed in Yanshanian period. The tungsten mineralization represented by the Nanling and Ganbei metallogenic belts mainly occurred from the Late Jurassic to the early stage of Early Cretaceous (160 ~ 120 Ma), while the most important tin mineralization in South China is composed of the Late Cretaceous (110 ~ 80 Ma, peak period 90 ~ 80 Ma) tin deposits in the Youjiang Basin and the Late Jurassic (160 ~ 150 Ma) tin deposits in the Nanling metallogenic belt. An important feature of granite-related tungsten and tin deposits in South China is that a variety of different mineralization styles or metal assemblages occur in the same deposit or orefield, and understand of these features is of great significance to guide ore exploration. In this regard, by taking Yaogangxian, Maoping-Taoxikeng, Shizhuyuan, Dachang and Gejiu as examples, this paper puts forward several metallogenic models and prospecting directions for granite-related tungsten and tin mineralization in South China based on recent exploration progresses and metallogenic studies. In addition, on the base of petrological and mineralogical characteristics of tungsten and tin granites, this paper summarizes the chemical characteristics of fluid and melt of granitic magmatic hydrothermal system and accordingly explores the fluid and melt inclusion chemical index for evaluating the tungsten and tin mineralization potential of granite. This may expand the exploration index for granite-related tungsten and tin deposits.
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Temporal and spatial distribution patterns of granite-associated tin deposits and ore-forming process in Southwest Yunnan, China

SUN Xiang, LU Leilei), SI Xiaobo), XIAO Ke), Li Qiang), ZHENG Mingjun), SUN Haoyu), HUANG Yunpeng)

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The Southwest Yunnan tin belt has a similar ore-forming geological background to the globally famous Southeast Asian tin belt, and its ore-forming regularities and resource potential have therefore always been a research hotspot. Based on previous research, this study explores the temporal and spatial distribution patterns and ore-forming processes of the Southwest Yunnan tin belt. The tin deposits in Southwest Yunnan are mainly distributed in the Tengchong block, Baoshan block, and Changning-Menglian orogenic belt. Literature geochronological data shows that three periods of tin mineralization occurred in the Tengchong block, i.e., 125-120 Ma, 75-68 Ma, and 52-47 Ma, respectively. Our recent geochronological data identifies two periods of tin mineralization in the Baoshan block including the late Cenozoic (~32-24 Ma) and the late Cretaceous (~75 Ma), and Triassic (~235-220 Ma) tin mineralization in the Triassic Lincang granite batholith in the eastern Changning-Menglian orogenic belt. We propose that the formation of Triassic granite and associated tin deposits is related to the collision after the closure of the Paleo-Tethys Ocean, the formation of Early Cretaceous granite and associated tin deposits in the Tengchong and Baoshan blocks is related to the collision after the closure of the Meso-Tethys Ocean, the formation of Late Cretaceous to Paleogene granite and associated tin deposits is related to the subduction the Neo-Tethys Ocean and the subsequent slab rollback, and the Late Cenozoic tin mineralization in the Baoshan block is related to strike-slip fault activity. Generally, the tin deposits in Southwest Yunnan are closely related to highly differentiated two-mica granites or biotite granites in the late stage of multiphase granite plutons, which is consistent with the characteristics of tin ore belts in Southeast Asia and Southern China. Our research reveal that the tin mineralization period in the Triassic granite of the Baoshan block is significantly later than that of the surrounding rocks, so attention should be paid to strengthening the exploration and evaluation of the granite plutons and tin deposits during the mineralization period. In addition, tin deposits with mineralization ages of ~90-85 Ma have been discovered in the Sibumasu Terrane in Myanmar, while tin deposits of the same age have not yet been found in the Baoshan block in China, which deserves further theoretical research and exploration evaluation.
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Thermodynamic and Trace element modelling of partial melting of eclogite: A case study of Xitieshan terrane, North Qaidam, China

JIANG Xiaocong, LI Chuanzhi, YU Shengyao, PENG Yinbiao, JIANG Xingzhou, GAO Xiangyu, WANG Lintao

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Anatexis is a common phenomenon in high-grade metamorphic rocks and one of the important geological processes for tectonic evolution of orogenic belt. Eclogite is the main rock type for studying continental subduction, ultra-high pressure(UHP) metamorphism and crust-mantle interaction. Its partial melting is closely related to crustal growth, slab exhumation, and element transport and distribution in a continental subduction channel. In-situ and in source leucosomes representing the anatexis is generally retained in the Xitieshan eclogite in the North Qaidam UHP metamorphic belt, which provides favorable conditions for understanding the effect of the anatexis of the UHP eclogite. In this paper, zircon U-Pb chronology analysis was used for the leucosome in Xitieshan eclogite. LA-ICP-MS U-Pb dating yielded a weighted mean 206^Pb/²³⁸U age of 425.3±5.9Ma (MSWD=0.74), representing the formation age of leucosome.The anatexis of eclogite in the Xiteshan terrane was simulated by thermodynamic and trace element modelling, and combined with the retrograde P-T paths of eclogite in the area, the temperature and pressure conditions of equilibrium crystallization of Na-rich leucosome in eclogite were limited at 12.27~10.71kbar/794~797℃. The initial partial melting of the eclogite occurred at the eclogite phase (~19.54kbar/~780℃), and the partial melt formed in the UHP eclogite through breakdown of omphacite with minor involvement of phengite and zoisite in the process of temperature rise and pressure fall. During the whole partial melting process, the eclogite produced ~8~9vol% melt, meeting the minimum requirements of the melt migration, indicating that the eclogite may have little contributionto the source area of the syn-exhumation granite in the Xiteshan terrane.
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Discussion on S-Pb-H-O-He-Ar isotope composition and genesis of the Sanhetun gold deposit in Heilongjiang Province

liubaoshan

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Sanhetun gold deposit is located in Nenjiang County, Heilongjiang Province. The ore body occurs in the late Triassic granitic mylonite, near the contact zone between the volcanic rocks of the lower Cretaceous Guanghua Formation and the late Triassic granitic mylonite. In order to discuss the source of ore-forming fluid, this work systematically studied the S, Pb, H, O isotopes and inert gas He, Ar isotopic compositions in different minerals collected. Stable isotope results show that: δ34S is between -4.4‰~4.9 ‰，which is similar to meteorite sulfur δ34S value,reflects the contribution of sulfur from deep magma; 206Pb/204Pb of Pyrite =17.284-18~180290，207Pb/204Pb=15.505~15.561,208Pb/204Pb=37.656~38.116; 206Pb/204Pb of Quartz=18.206~ 18.449,207Pb/204Pb=15.526~15.652,208Pb/204Pb=38.050~38.648, which indicates that the ore-forming material mainly comes from mantle; H, O isotopes of Quartz δ DV-SMOW value is - 77.5 ‰~- 96.3 ‰, δ 18OV-SMOW is 7.4 ‰~11.6 ‰, δ18OH2O is - 0.2 ‰~4.8 ‰, which reflects that the ore-forming fluid mainly comes from atmospheric precipitation, and some magmatic water also participates; The 3He/4He ratio of Pyrite fluid inclusions is 1.19～1.54R/Ra, tens to more than hundreds times higher than the 3He/4He ratio of the crust, but obviously lower than the 3He/4He ratio of mantle fluid; 40Ar/36Ar=608.5～922.6, higher than the 40Ar/36Ar composition of crustal fluid (40Ar/36Ar＞295.5);The 40Ar*/4He ratio is 0.14～1.56, with an average value of 0.95. The 40Ar*/4He (0.14) of SHT19 sample data is close to the 40Ar*/4He (0.2) fluid of the crust, and the 40Ar */4He (0.88～1.56) of other samples is much higher than the mantle (0.33～0.56) fluid, indicating that the ore-forming fluid may be mainly meteoric water, but also the crust and deep mantle fluid. According to the regional metallogenic epoch, the Sanhetun gold deposit was formed in the late Early Cretaceous, and the source of ore-forming materials was closely related to the magmatic activity in the Guanghua period of the Early Cretaceous.
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Constraints of multi-stage tectonic deformationalevents on enrichment and mineralization of the Dahenglu Cu-Co ore deposit in Jinan

Zhonghua Tian, Fulai Liu, Chaohui Liu, Zhiyong Zhu, Huining Wang

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Cobalt ore deposit is one of the significant strategic metal minerals. The in-depth study of its mineralization (such as the relationship between structure and mineralization) can provide the theoretical basis for guiding ore prospecting. Based on the research of Dahenglu Cu-Co mine in Sanchahe Village, Sandaogou Town, Baishan City, Jilin Province, China, the field structural deciphering, drilling and core data analysis, TIMA test of drilled sections and regional rock chronology are mainly carried out. Structural deciphering shows that the country rock of Dahenglu Cu-Co mine includes bedding-cleavage interaction, S1 cleavage, and crenulation cleavage. A large number of F2 closed folds, thrust faults, and their related asymmetric folds, and overturned folds are developed in the Dahenglu Cu-Co mine based on drilling holes and cores analysis. TESCAN Integrated Mineral Analyzer (TIMA) experiments of thin section samples from boreholes and exploratory trenches show that Co-containing fluids are enriched in the low-angle thrust faults, the ductile shear domain of overturned folds, and the hinge zone of fault-related folds. These works show that the NE low-angle thrust fault and fault-related fold play a key role in controlling the enrichment of the Dahenglu Cu-Co deposit. Combined with previous studies, a large number of regional geological data, and the relevant geochronological data show that: (1) the ore-controlling structures such as thrust fault and fold in the mine area are the products of the Paleoproterozoic tectonic event; (2) The restriction of Mesozoic tectonic events on mineralization (Cu-Co ore re-enrichment) may come from the large-scale extension produced by the Cretaceous tectonic event.
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Classification and stratigraphic correlation of Stromatolites in Kesuer formation , Dongchagou village, Huangzhong district, Qinghai province

Dan Haowen, Bao Guangpu, Dong Lin, Qin Shujian

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Stromatolites, often considered among the oldest traces of life on Earth, provide valuable paleontological insights for chronostratigraphic correlation. They are particularly useful for stratigraphic correlation in Mesoproterozoic basins. The Kesuer Formation, part of the Huashishan Group in Dongchagou Village, Huangzhong County, Xining City, Qinghai Province, primarily consists of dolomitic carbonate assemblages with a large quantity of stromatolites. According to the classification method summarized by Cao Ruiji and Yuan Xunlai, nine distinct stromatolite genera have been identified in this area: Baicalia, Chihsienella, Anabaria, Tielingella, Conicodomenia, Tungussia, Colonnella, Stratifera and Cryptozoon. This stromatolite assemblage closely resembles the late Mesoproterozoic Tieling Formation stromatolite assemblage in the Jixian System, and shares similarities with late Mesoproterozoic to early Neoproterozoic strata stromatolite assemblage in China. As a result, the age of the Kesuer Formation in the Huashishan Group can be determined as late Mesoproterozoic. The first report of Qinghai stromatolites broadens the known distribution of Mesoproterozoic stromatolites in China and globally, updating the vertical distribution of common stromatolite genera and species. These findings hold significant implications for stratigraphic correlation.
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Zircon U-Pb Geochronology, Geochemistry, and Sr-Nd-Hf isotopic characteristics of the Permian-Triassic granitic intrusions in Huade area, Inner Mongolia, NE China: Constraints on the tectonic evolution of the Paleo-Asian Ocean

jin shengkai, LIU Bo, MA Ming, YIN jiale

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This paper presents detailed petrological, zircon U-Pb chronological, whole-rock geochemical and Sr-Nd-Hf isotopic studies of the Permian-Triassic granitic intrusions in Huade county, Inner Mongolia. The geochemical and isotopic features indicate that the studied intrusions were derived from a Paleo- to Mesoproterozoic crustal source of the North China craton. The Bayinchahan intrusions experienced magma mixing during the magma upwelling, the Baiyintla intrusions were S-type granite formed by partial melting of metamorphic greywacke during the crustal thickening, the Maohuqing intrusions were I-type granite, and the Kangjiadi and the Zhangwanliang intrusions were A-type granite. Zircon dating results indicate that the Bayinchahan, Baiyintela, Maohuqing, Zhangwanliang and Kangjiadi plutons were formed in the Early Permian (276±1Ma), the Middle Permian (270±1Ma), the Late Permian (254±1Ma), the Early Triassic (248±1Ma) and the Late Triassic (229±1Ma), respectively. Combining with previous studies, we concluded that the study area experienced subduction, subduction-collision, continuous collision and post-orogenic extension during the Early Permian to Late Triassic. The closing time of the eastern part of the Paleo-Asian Ocean in the study area should be the late Middle Permian.
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Sandbox modeling on development of source-to-sink system along strike-slip fault

YAN Bing, JIA Dong, LAI Wen, WANG Maomao

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The combination of uplift denudation area and piedmont depositional area bounded by strike-slip fault is one of the important types of basin-mountain system. Due to the continuous relative slip between the two plates of the strike-slip fault, the spatial relationship between the source and sedimentary area on both sides of the strike-slip fault constantly changes as the fault slipped. The coupling mechanism between source and sedimentary systems on both sides of the strike-slip fault is a problem to be studied. To investigate this problem, a simplified geomorphic sandbox experiment was designed to reveal the distribution of sediment eroded from the intrusive rock masses in the source area. The experimental results showed that the distribution area of the sedimentary signal of the intrusive rock masses in the sedimentary area was affected by many factors, including the shape of the piedmont alluvial fan and the distribution of the rock masses in different drainages. Due to the fan-shaped development of the alluvial sediment, the sedimentary signals were distributed in a wider range further away from the strike-slip fault. When the same rock masses were distributed in different drainage basins, its sediment was distributed in two alluvial fans, which makes its sedimentary signal distribution range wider. Conversely, the sedimentary area of an alluvial fan became narrower when restricted by larger adjacent fans. Due to the above relationships, the calculated strike-slip rate might be underestimated or overestimated using the offset amount between the strata with sedimentary signal and the source rock mass. The experiment in this paper provide an important model for studying the source-to-sink system bounded by strike-slip faults.
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Geochronology, geochemistry and geological significance of Paleoproterozoic porphyritic granites in Quibala area, Angola Shield

Jin Lijie, Zhang Hongrui, Luo Dike, Jia Pengfei, Liu Wei, Wang zisheng, Li Jinzhen, Zhou Yonggang, Jiang Zhenguo

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Angola has experienced several tectonic cycles in the Precambrian period, among which the paleoproterozoic Eburnean cycle is the most important one, which has important geological significance for understanding its tectonic evolution process. Due to the lack of accurate chronological and geochemical data, the formation age of magmatic rocks in the central Eburnean area is still not supported by effective data, which is also one of the main reasons for the unclear genesis and tectonic evolution of rocks. In this paper, the Quibala porphyritic granites in Eburnean area in the central Angolan Shield are studied in petrology, chronology and geochemistry. LA-ICP-MS zircon U-Pb chronology shows that the Quibala porphyritic granite was formed from 1987 to 1956Ma, which represents the main activity time of Eburnean movement in the Angora Shield. The geochemical study shows that porphyritic granite has high silicon, alkali, iron content, Ba, Sr, P, Ti elements deficit and Rb, Th, K, Hf elements enrichment, the total content of rare earth elements is high, indicating that it is A-type granite. In addition, the xenoliths of ancient basement such as gneiss, diorite inclusions containing potassium feldspar phenocrysts, and the ratios of Rb/Nb, Th/U, Nb/Ta and other characteristic elements indicate that the xenoliths may be the result of the mixing of crust-mantle materials. The NB-Y-3Ga and Rb- (Y+Nb) diagrams show that the granite porphyry was formed in the paleoproterozoic post-collision extensional environment.
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TECTONIC PROPOGATION AND BASIN EVOLUTION DURING THE EXTENSION AND BREAKUP OF THE SOUTH CHINA SEA

LUO PAN, REN JIANYE, LEI CHAO

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In order to clarify the time-space evolution of tectonic activities with the ocean continental transition, we interpret and analysis 2 long seismic lines which are across the conjugate margin of South China Sea. Four first order interfaces have been recognized in the ocean continental transition of SCS: Tb, SD, PD and Bi. These 4 first order horizons separated the basins on continental margin into different proto-basins: the early rifted basin (Tb-SD), the later detachment basin (SD-PD) and the transfer basin (PD-Bi). According to the comparison of syn-tectonic sequences in different domains in one seismic line, the tectonic activities youngling from continent to ocean. According to the comparison the syn-tectonic sequences in same domain between different lines, the tectonic activities youngling along the seafloor spreading direction. Thus, during the seafloor spreading stage, the lithosphere extension deformation propagated not only from continent to ocean, but also along the seafloor spreading direction.
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Genesis of Koktokay rare metal deposit（Xinjiang）and concealed orebody forecast in its southern district: evidence from geology, remote sensing and geophysics

Shen Ping, He Lanfang, Jin linhai, Pan hongdi, Luo yaoqing, Feng haoxuan, Li changhao, Ma huadong, Baiyingxiong, Wang wei

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The Koktokay in Xinjiang is a famous pegmatitic-type rare metal deposit in the world. The genesis of the pegmatites has been controversial，and the rare-metal resources have been exhausted for many years. Hence，breakthroughs are urgently needed in both theories and prospection. In this study，we conducted geological and geochemical research on the Middle Ordovician metamorphic rocks of Habahe Group and Triassic rare-metal granites in the mining area，as well as remote sensing data interpretation，geophysical investigation， and hidden ore prediction. The metamorphic rocks of the Habahe Group are mainly composed of mica schist. Their trace element contents are similar to that of the continental crust，but are slightly enriched in Li and Cs. It is impossible to form mineralizing magma through partial melting of these metamorphic rocks. The Triassic rare-metal granite mainly consists of muscovite albite granite with minor albite granite，which originated from a deep magma chamber. During the upward migration process， the magma underwent flow differentiation to form volatile-rich，highly differentiated magmas，and then intruded locally to form granite branches. The rare-metal granite is the same as the No. 3 pegmatite in emplacement age，mineral assemblages and compositions, indicating a same magma source with the pegmatite being a product of higher differentiation. Various remote sensing data interpretation results show several ring images in the Koktokay area which could indicate the ring structures at depth. The pegmatites and rare-metal granites occurred in these ring structures，indicating that the host magmatic activity at Koktogay is associated with the ring structures. The Magnetotelluric (MT) shows that there are low-resistivity anomalous bodies below 15 km at depth，which could be a residual magma chamber or melting zone where the granite magma derived. The Audio-frequency Magnetotelluric (AMT) shows significant low-resistivity anomalous bodies occurred in the depth and probably caused by faults and hydrothermal alterations. Based on the results of the above geological，remote sensing，and geophysical research，we predict that there might be fault-magma channels in depth of ring-shaped structures，in which granitic magma and related rare metal orebodies are developed.
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Spiral chirality study of three-lobes helical tube Anabarites cf. tripartitus from the Cambrian Age 2 in Three Gorges

pengjiaxin, zhaoxiaofang, guojunfeng, qiangyaqin, songzuchen, sunjie, hanjian

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Helical chirality is common in living organisms today and the fossil record, however this phenomenon has remained almost unstudied, especially in small shelly fossils from the early Cambrian. Anabaritids are a kind of tubular fossils with distinct triradial symmetry, which are known from the early Cambrian strata worldwide. Previous studies on some helical species of anabaritids were mostly limited to morphological descriptions, and the reasons for their helical chirality were poorly discussed. Based on 111 specimens of Anabarites cf. tripartitus from Member 5 of the Yanjiahe Formation (Cambrian Stage 2) in Three Gorges area of Hubei Province, China, the mechanism of their fixed right-handed (dextral) spiral chirality was investigated. The cause of right-handed helical chirality should be inferred from the biological factors (e.g. functional morphology, molecular developmental biology) perspective of molecular genetics, instead of external environmental factors (e.g. water change, taphonomy, Coriolis force).
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Petrogenesis of the Early Carboniferous diorite from Diyanmiao ophiolite belt ，Inner Mongolia and Paleo-Asian Ocean intra-oceanic subduction

liuzhibin, Liyingjie, Cao Kan, Wangjinfang, Dongpeipei, Zhangxiawei, Wangshuai

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Due to the lack of reliable discovery and systematic study of SSZ ophiolite and Intra-oceanic arc igneous rock, which restricts the further understanding of the Paleozoic subduction extinction process of the eastern part of the paleo Asian ocean. The Bagahaer Early Carboniferous diorite distributed along the Hegenshan suture zone in the eastern part of the Xingmeng Orogenic Belt was discovered to be outcropped in the northern section of Diyanmiao SSZ ophiolite in Xiwuqi, Inner Mongolia. It belongs to Calc alka series, chemically characterized by 57.71%~61.24% of SiO2, 15.58%~16.26% of Al2O3, and 3.30%~4.23% of MgO, with relative rich in Na2O（3.29%~3.84%）poor in K2O（1.05%~1.69%） and high ratio of Na2O/K2O（2.18~3.95）.The diorite relatively enriched large ion lithophile elements（LILE）Rb、Ba、K and depleted high field strength elements（HFSE）Nb、Ta、P and Ti, etc. In addition, it features low ∑REE（85.19×10-6~98.21×10-6）and clear REE fractionation（（La/Yb）N=3.08~3.99）, without obvious Eu anomaly（δEu =0.61~0.82）. Eighteen zircon grains from the diorite yielded a weighted mean 206Pb/238U age of 324.2±1.8 Ma, indicating an Early Carboniferous age. The petrological and geochemical characteristics of the diorite have obvious similarities and progressively evolved relationships with the fore-arc basalt (FAB) and boninite in the Diyanmiao SSZ-type ophiolite. The discovery and confirmation of Bagahaer Early Carboniferous intra-oceanic arc diorite in the Diyanmiao SSZ-type ophiolite reveal the transition from initial arc to mature arc of the eastern Paleo-Asian Ocean intra-oceanic subduction during the late Paleozoic.
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Occurrence and ore-forming mechanism of beryllium in the Baishawo Be-Li-Nb-Ta pegmatite deposit in northeastern Hunan, South China

Fanzhiwei, Xiong Yi-Qu, Shao Yong-Jun, Wen Chun-Hua

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Beryllium (Be), as a critical element, is an essential industrial raw material in advanced fields and the new energy industry. China is a major beryllium consumer with high external dependence, and beryllium resources are in short supply. The recently discovered Baishawo Be-Li-Nb-Ta deposit, located in the northeast of Hunan, is a large pegmatite type rare metal deposit. Previous studies show that the beryl is the dominant beryllium-bearing mineral occurring in pegmatite, whereas the occurrence state and ore-forming mechanism of beryllium are still unclear. Here, we combined field geological survey, optical microscope observation, SEM, X-ray maps, TIMA, EPMA and LA-ICP-MS analysis, to investigate the petrographic and mineralogical features of beryl, tourmaline, quartz, albite, and mica of 3# pegmatite dike in the Baishawo deposit. The results show that Be occurs not only in beryl as an independent mineral but also in tourmaline, quartz, albite, and mica as an isomorphic form. Beryl mainly distributes in the wall and intermediate zones of 3# pegmatite. The wall zone beryl is light green in color with 2 × 3 × 5 cm in size and coexists with albite, muscovite, and garnet. The beryl crystal from the intermediate zone has large grain size (~50 cm), and presents a short columnar, with longitudinal lines parallel to the c-axis on the crystal surface. The beryl from the wall zone has BeO, Li2O, and Cs2O content of 12.87%-14.01%, 0.14%-0.33%, and 0.05%-0.12%, respectively. The BeO content in beryl from the intermediate zone is 13.38%-13.96%, and the contents of Li2O and Cs2O are slightly higher than those in the wall zone, which are 0.25%-0.39% and 0.13%-0.39%, respectively. Additionally, the concentration of Be in quartz (0.20-7.13 ppm, with an average of 2.50 ppm) is lower than that of other Be-bearing minerals. Tourmaline (4.13-8.73 ppm, with an average of 5.94 ppm, The average content of Be in albite (4.74 ppm) was close to that in albite (1.22-6.98 pm, average 4.54 ppm). The content of Be in muscovite (16.9-53.8 ppm, average 21.77 ppm) was the highest, with up to 53.8 ppm. It is considered that the 3# pegmatite dike belongs to LCT (Li-Cs-Ta) pegmatite and is of granitic melt crystallization differentiation origin for wall zone pegmatite, while the pegmatite in the intermediate zone is in the magmatic-hydrothermal transition stage, which is subject to the metasomatism of late hydrothermal fluid. In the Baishawo deposit, beryl coexists with alkaline feldspars such as albite, and the BeO contents is up to 13.44%, which has a significant industrial value and can be used for green selection and smelting by acid flotation. This study provides a reference for the occurrence and genesis of beryllium in rare metal pegmatite deposits, and also a scientific basis for the exploration, development, evaluation, and prediction of beryllium resources in rare metal pegmatite deposits.
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Rb mineralization during magmatic differentiation: insight from mineralogical study on Ganfang rare metal granite, Jiangxi Province

Xu Jing, Hou Wenda, Wang Liyuan, Zhao Taiping, Chen Suyu, Tian Liming

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The Rb mineralization is associated with rare metal granite. However, widespread hydrothermal alteration in the late evolution of rare metal granite makes it difficult to distinguish the magmatic process from the hydrothermal process. It is still unclear whether the rare metal mineralization is dominated by magmatic differentiation or hydrothermal metasomatism. The Ganfang inrustions in Jiangxi Province is an important rare metal metallogenic area, where a series of Li-Rb rare metal deposits (mineralization) have been discovered, and the mineralization mechanism of rare metals is not clear yet. This paper takes both granite-type Rb (Baiguo, Dagang, and Nanmukeng) and aplite-type Rb (Fuhua, Tongan) mineralization from Ganfang intrusion as the case study. The detailed mineralogy texture and composition of feldspars and micas have been analyzed by automatic mineral scanning system, electron probe and LA-ICP-MS. The results show that micas are the main carriers of Rb (1683~12047 ×10-6), and the contents of Rb in feldspars are lower. The Rb content of K-feldspar is 1683~4051 ×10-6, whereas albite contains almost no Rb concentration (1.82~89.94 ×10-6). The Rb-bearing micas transfer from muscovite, though Li-phengite and zinnwaldite, to lepidolite, in which substituted mechanisms for Li are 2Li+ + IVSi4+ → VIAl3+ + VIAl3+ + □ and Li+ + Fe2+ → VIAl3+ + □, and for Rb is Rb+/ Na+/ Cs+ → K+. The mineral textures and compositions record both magma crystallization differentiation and fluid metasomatism for Ganfang granites; however, the former was the key enrichment mechanism for Rb as well as Li.
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Heterogeneous strain distribution in a continental subduction channel: Records from ultrahigh-pressure metamorphic rocks in the Dabie Mountains

Peidong Li, Qin Wang, Meiqian Wu

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As the shear zone between the subducting and overlying plates, a subduction channel is the pathway for exhumation of high- and ultrahigh-pressure (UHP) metamorphic rocks and deep fluid/melt activity. Due to the wide exposure and variable deformation degree of UHP metamorphic rocks, the Dabie orogenic belt provides an ideal area to investigate metamorphism and deformation processes in a continental subduction channel. Here we summarized previous petrological and geochronological studies in the Shuanghe area of the central Dabie orogenic belt and carried out field mapping, strain analysis and 3D structural reconstruction in this region. Combining deformation with P-T-t paths of UHP rocks, three ductile deformation phases during exhumation of UHP rocks are identified. A kilometer-scale sheath fold of eclogite facies (D1) in the northern Shuanghe area is characterized by the SE-plunging fold axis with a dipping angle of ~20o and a top-to-the-NW shear sense. This indicates that high fluid activity during the initial exhumation significantly reduced viscosity of eclogite, leading to the simultaneous ductile deformation of eclogites and surrounding rocks. The following deformation phase under amphibolite facies (D2) overprinted the D1 fabrics by the continuous top-to-the-NW shearing. Strain was localized in incompetent rocks such as gneisses, schists and marbles, whereas eclogites appeared as tectonic boudins. The top-to-the-SE detachment (D3) mainly occurred in schists under greenschist facies, which may be related with formation of the granitic gneiss dome in the northern Dabie orogenic belt in the Early Cretaceous. In the southern Shuanghe area, zircon U-Pb dating of weakly deformed granitic gneiss revealed the crystallization age of 757±14 Ma and the metamorphic age of 216~240 Ma, which are consistent with strongly sheared coesite-bearing granitic gneiss in the northern Shuanghe area. Hence these weakly deformed granitic gneiss also experienced the Triassic UHP metamorphism and the amphibolite facies retrograde metamorphism. Calculation of the effective viscosity of felsic gneiss indicates that dry alkali-feldspar granitic gneiss is stronger than biotite-plagioclase gneiss. Water can significantly reduce the effective viscosity of UHP rocks. If localized fluid activity could not weaken the large-scale alkali-feldspar granite gneiss pluton, strain localization occurs in biotite-plagioclase gneiss. Therefore, strain distribution in a continental subduction channel is controlled by mineral assemblage, fluid activity and volume of a rock body.
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Petrogenesis of Mesozoic intermediate-acid intrusive rocks in the Tongling ore concentration area of Anhui Province: Evidence from geochemistry of zircon and apatite

XU xiaochun, Yu wen, JIN linsen, XIA cailian, XIE Qiaoqin, Yan Jun

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Mesozoic intermediate-acid intrusive rocks are widely developed in the Tongling ore concentration area of Anhui Province, and they are closely related to the polymetallic-copper mineralization. A large number of previous studies have been issued on the genesis of these intrusive rocks, but there are still some controversies. In this paper, Tongguanshan and Dongguashan quartz diorite and Fenghuangshan and Hucun granodiorite are selected as research objects to further explore their genetic mechanism. Based on the research results of major and trace elements and Sr-Nd isotope of the whole rocks, a special effort is made to investigate the geochemical characteristics of zircon and apatite from these rocks. Integrating the previous research results and the analysis data of our job, it can be concluded that the Mesozoic intermediate-acid intrusive rocks have similar major and trace element compositions, are all of high-K calc-alkaline rock series with characteristics of arc magmatic rocks and adakitic like rocks, are also enriched in Sr-Nd isotope compositions. These geochemical characteristics combining with the petrological characteristics of mafic microgranular enclaves（MMEs）and antiband structures of amphibole and plagioclase indicate that their parental magma was generated by the mixing of mafic magma and felsic magma. Our new analytical results are as follows: the U-Pb ages of the inherited zircons are mainly in two ranges of 1.0Ga～0.8Ga and 2.4Ga～2.0Ga, the εHf(t) values of zircon grains are -20.5～-5.1 corresponding with calculated Hf two-stage model ages between 1.5Ga～2.9Ga, and the δ18O values of zircon are 5.93‰～8.85‰, the apatites have high Cl contents (average 0.3wt%) with relatively high Cl/F values (0.052～0.244), high REE contents (1714×10-6～5903×10-6) and negative δEu values (0.26～0.68). Based on the above-mentioned geochemical characteristics of major and trace elements and Sr-Nd isotopes of whole rocks, and the geochemical characteristics of singer minerals zircon and apatite obtained from this job, combined with the regional geological tectonic evolution, the different previous views on the genesis of the Mesozoic intermediate-acid intrusive rocks in the area are debated and questioned, and proposed our own point of view. It is held that the Mesozoic intermediate-acid intrusive rocks in the Tongling ore concentration area were derived from a mixture of crust-derived and mantle-derived magma, that is, the mixing of enriched lithospheric mantle derived magma and Neoproterozoic juvenile arc crustal derived magma, a small amount of ancient crustal materials from Paleo-Proterozoic to Meso-Proterozoic had also been mixed in the magma ascending process. The enriched lithospheric mantle sources magma was derived from the subducted oceanic crust or the fluid metasomatic overlying lithospheric mantle when Cathaysia oceanic slab beneath the Yangtze craton in the Neoproterozoic era, but not the Paleo-Pacific slab subducted into South China plate in the Mesozoic era. The roll-back after subduction of the Mesozoic Paleo-Pacific slab was the geodynamic mechanism that led to the ancient orogenic belt extending after thickening, the lithospheric mantle thinning and melting.
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Structural coupling between the Qaidam Basin and bordering orogenic belts in the Cenozoic

WU Lei, YANG Huitong, ZHANG Yongshu, ZHANG Junyong, WEI Yanyan, HUANG Kai, CAO Fengwei, GE Mengjia, YE Yuhui, CHEN Yan, TANG Jianchao, LIN Xiubin, XIAO Ancheng, CHEN Hanlin, YANG Shufeng

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A series of old orogenic belts and basins were rejuvenated in the context of Cenozoic India-Asia convergence forming in the periphery of the Tibetan Plateau the largest intracontinental compressional zone, which is named as the Circum-Tibetan Plateau Basin and Orogen System (CTPBOS). The formation process and underlying mechanism of the CTPBOS are of large significance in advancing our knowledge of how continental collision impacts deformation in the interior of a continent. The Qaidam Basin is an important Cenozoic sedimentary basin in West China, and bordered by huge orogenic belts. They together form the main body of the northeastern part of the CTPBOS. In this study, we combined the upper-crustal and deep (Moho) deformation through latest exploration seismic data, surface geology and published deep geophysical imaging, portrayed the structural coupling between the Qaidam Basin and the three surrounding orogenic belts in the lithospheric scale, and accordingly explored the basin-mountain convergence process and underlying mechanism of the CTPBOS. In upper-crustal scale, a set of basement-involved, high-angle reverse faults developed in the conjunction regions of the Qaidam Basin and the Qiman Tagh-East Kunlun Shan to the south and the South Qilian Shan to the northeast. These faults, which generally dip toward the mountains, are dominated by vertical basement rise with limited horizontal shortening, and were initiated in the Early Cenozoic. In the lower crust and lithospheric mantle, deep faults dipping toward the basin developed and offset the Moho of the Qaidam Basin and adjacent mountains. These observations imply lithospheric-scale wedge tectonics, which are characterized by the Qaidam lithosphere tapering into the thickened lower crust of the Qiman Tagh – East Kunlun Shan and the South Qilian Shan, and formed in response to the lateral heterogeneity of the lithospheric strength between basins and orogenic belts. Different from the above contraction-dominated basin-orogen systems, the Qaidam Basin and the Altyn Shan to the northwest are simply separated by the huge sinistral lithospheric-scale Altyn Tagh fault, which served as the lateral slip boundary during the formation and deformation of the Qaidam Basin.
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Distribution and enrichment mechanism of lithium in meta-sedimentary rocks in the Jiangnan Orogen and implication for lithium mineralization

Gou Shulin, Yu Jin-hai, Cai Yuanfeng, Jiang Wei, Mao Zhiqi

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The Jiangnan orogen is one of the important metallogenic belts of rare metals in China. Several granite-pegmatite type lithium rare metal deposits have been found in this belt. The enrichment of lithium and other rare metal elements in the basement rocks is the material basis for the mineralization of the granite-pegmatite type lithium rare metal deposit, but the distribution and enrichment mechanism of lithium in the basement rocks of the Jiangnan orogen are still unclear. In this paper, the Neoproterozoic Lengjiaxi Group, Shuangqiaoshan Group, Xikou Group and Banxi Group meta-sedimentary rocks and the Xingzi complex in the eastern section of Jiangnan orogen are investigated in detail. These basement rocks include metasandstone, argillite, phyllite, mica schist and less gneiss. Geochemical analysis results show that meta-sedimentary rocks of the Lengjiaxi, Shuangqiaoshan and Xikou groups have similar compositions, and metasandstone, mica schist and gneiss have higher SiO2 and lower TiO2, Al2O3, K2O, MgO and Fe2O3Tthan argillite and phyllite. The argillite and phyllite generally contain higher rare metal element contents, with mean Li content up to 61.8×10-6^,whereas the metasandstones have lower Li abundances with a mean of 44.9×10-6^.The Banxi Group has lower rare metal element contents (CLi = 30.8×10-6^). Li contents of meta-sedimentary rocks of the Lengjiaxi, Shuangqiaoshan and Xikou groups exhibit a good positive correlation with the chemical index of alteration (CIA), MgO, Fe2O3T^{, and with} the clay minerals in the rocks, especially chlorite. Therefore, Li concentrations of sedimentary rocks are obviously controlled by chemical weathering, that is, the mechanism of Li enrichment is the adsorption of clay minerals, especially montmorillonite and chlorite. The majority of Li concentrate in biotite, muscovite and staurolite in middle- and high-grade metamorphic rocks. The modeling of partial melting of the meta-sedimentary rocks of the Lengjiaxi Group shows that the decomposition and melting of mica minerals are the most important cause of the increase of Li content in the melt during partial melting. The Li concentration of the melt reaches the peak when the mica is completely melted off. Continued melting will dilute Li content in the melt. Li concentration in the melt are affected greatly by Li content in the source and the partial melting degree, which depends on major element compositions of the source rocks and P-T conditions. The modelling results also show that increasing pressure is conducive to the Li enrichment in the melt. Under the conditions of 1.0 GPa and 840℃, the melting degree reaches 25%, and Li content of the melt is the highest, up to 4 times of Li content of the source. Therefore, partial melting under medium pressure facies series may be the most favorable for Li enrichment in melt.
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Physical modelling experiments of fold-thrust belts: A review based on previous and new experimental models

Jia Dong, Yang Shufeng, Yin Hongwei, Li Yiquan, Wu Xiaojun, Xie Guoai, Li Yinqi

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The fold-thrust belt is rich in oil and gas resources, which contains about 14% of the world's proven oil and gas reserves. It has been more than 200 years since geologists first confirmed that folds are formed by horizontal compression deformation of rock strata in 1815, and the physical modelling experiment research on fold-thrust belts is undoubtedly one of the most effective research fields. In this paper, from tracing the pioneers of early modelling experiments to summarizing the relevant research progress in recent twenty years, the main contribution of physical modelling experiments to the development of foreland fold-thrust belt structure theory is emphatically analyzed and commented. It is emphasized that the critical wedge theory of orogenic belt, the strength of basement detachment layer, fluid overpressure and cohesive strength of deformed rock layers control the tectonic deformation process. The experimental results are as follows: (1) the growth law of structural deformation in fold-thrust belt; (2) Tectonic deformation mechanism of fold thrust belt; (3) The main controlling factors of structural deformation in the fold-thrust belt. Our purpose is to provide fascinating experimental research results of physical modelling, attract more researchers at present and in the future to understand and attach importance to physical modelling, and promote basin structure research to make a leap from qualitative to quantitative, from two-dimensional to three-dimensional, from geometry and kinematics to dynamics step by step on the road of discipline development with the help of increasingly advanced experimental devices and technical methods.
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Rubidium and Cesium Enrichment in Lacustrine Sediments from Tibetan Salt Lakes: A Promising Resource

liqingkuan, wangjianping, fanqishun, qinzhanjie, yuhaoxue, shanfashou, yuanqin, duyongsheng

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Rubidium and cesium are critical metal mineral resources. Abundant Rb and Cs resources with low grade (< 10mg/L) occur in brines from Tibetan salt lakes. According to the supply relationship between hot springs and salt lakes, and their heterogeneity of Li, Rb, Cs concentrations, the speculation that Rb, Cs may be enriched in the lacustrine sediments is raised. To verify the hypothesis, 5 brine and sediment samples are collected from the Laguo Co, Nieer Co, Yibu Chaka, Dangqiong Co and Zhabuye Chaka salt lakes, respectively, and sequential extraction experiments are completed on the sediments. The Rb, Cs concentrations of brines and extracts, and the mineral assemblages of sediments are analyzed. Great heterogeneities exist between the Rb-Cs supply from the rivers and resources in the brines from Laguo Co, Yibu Chaka, Dangqiong Co salt lakes, indicating abundant Rb-Cs resources occur in the lacustrine sediments. The Rb and Cs concentrations in the sediments are apparently higher than those of the brines; Rb and Cs are enriched in the clay minerals (mainly illite), with the forms of the exchangeable basal position and the irreversible FES and interlayer positions. The potential Rb and Cs resources in lacustrine sediments are much higher than the requirements of large-scale Rb-Cs deposits, and the Rb and Cs concentrations in the clay minerals are reached up to several hundreds of ppm. Compared with the development status of Rb resources from the KCl products, and Cs resources from the geyserite, the Rb and Cs resources from lacustrine sediments in the Tibetan salt lakes show great resource potential. This work can be benefit to the high-efficient utilization of salt lake resources.
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Quantitative textural analysis of cumulates from the lower zone of the Bijigou intrusion in the northern margin of the Yangtze block: Constraints on the expulsion mechanism of interstitial liquid at the early stage of solidification of layered intrusions

WANG Jie, LI Zhongzhou, WANG Mengxi

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The expulsion of interstitial liquid from the crystal mush is closely related to the abundant crystallization of Fe-Ti oxides during the mid-late stage of the solidification of layered intrusions, yet the expulsion mechanism of interstitial liquid before the abundant crystallization of Fe-Ti oxides at the early stage is still enigmatic. The highly differentiated Bijigou intrusion in the northern margin of the Yangtze block is the largest layered intrusion with Fe-Ti-(V) mineralization in China at present. The lower zone (LZ), middle zone (MZ) and upper zone (UZ) of the Bijigou intrusion are mainly composed of plagioclase peridotite, gabbro and diorite, respectively. In this study, we analyzed the crystal size distributions (CSDs) and spatial distribution patterns (SDPs) for plagioclase and clinopyroxene of samples from the plagioclase peridotite unit in the LZ, in order to examine the expulsion mechanism of interstitial liquid from the crystal mush at the early stage of solidification of layered intrusions. Modeling results show that the fraction of trapped liquid (FTL) is 9% ~ 13% for samples from the plagioclase peridotite unit of the Bijigou intrusion, suggesting the interstitial liquid was effectively expelled from the crystal mush. The consistent slopes of the CSD curves for clinopyroxene and plagioclase of samples from the plagioclase peridotite unit mainly vary from ?3.36 to ?2.45 and from ?2.99 to ?1.87, respectively, and the variable intercepts are from 0.45 to 3.35 and from 1.06 to 2.83, respectively, similar to those for the mechanical compaction. In addition, the SDP R value (ratio of observed and predicted nearest neighbor distance of the same mineral) and the mineral mode except plagioclase/clinopyroxene of the samples are negatively correlated, consistent with the trend of mechanical compaction. Therefore, the expulsion of interstitial liquid at the early stage of solidification of the Bijigou intrusion is controlled by mechanical compaction. On the other hand, we compared the Bijigou intrusion with the Skaergaar, Sept Iles and Kiglapait layered intrusions in terms of the scale, fraction of trapped liquid, density contrast of the interstitial liquid and cumulus crystal, the relationship of accumulation rate and compaction rate, and the thickness of mush layer. We propose that the compaction plays a critical role in expelling the interstitial liquid at the early stage of solidification of layered intrusions if there’s no magma replenishment and convection, but the factors controlling the degree of compaction are distinct in different conditions. When the intrusion sizes are comparable, the onset of compaction is mainly controlled by the density contrast of interstitial liquid and cumulus crystals, with a higher degree of compaction for a greater density contrast. In addition, compaction is more likely to operate in large intrusions, rather than small ones at the early stage of solidification.
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Geochemistry of monazites from Be–Nb rare-element pegmatites in the Ningshan district, Middle-Segment of South Qinling Orogen: Implications for pegmatite genesis

Nie Xiao, Chen Lei, Guo Xianqing, Yu Tao, Wang Zongqi

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In recent years, several Be-Nb rare-element pegmatite dikes have been discovered in the Ningshan district of the Qinling orogenic belt through geological exploration. This study used scanning electron microscopy and electron probe microanalysis to investigate the mineralogical characteristics and mineral composition of monazite in Be-Nb pegmatite. The results indicate that monazite can be divided into two types. The first type is mainly occurred in the rock-forming minerals such as quartz and feldspar. Most of the first type monazite exhibit uniform internal backscattered electron (BSE) images, while a small portion may show oscillatory zoning. The first type monazite has a higher ThO2 content (7.0%–13.9%, averaging 10.5%). In contrast, the second type monazite also exhibits uniform internal BSE images, but with noticeably lower brightness compared to the first type. The second type monazite has a lower ThO2 content (0.9%–4.4%, averaging 2.2%). This indicates that the first type of monazite has a magmatic origin, while the second type has a hydrothermal origin. Higher concentrations of ThO2 in the primary magmatic monazite are associated with an increase in the brabantite molecule substitution. The U-Pb dating of the magmatic monazite yielded an age of 200.8 ± 2.1 Ma, representing the age of the pegmatite emplacement, which is slightly younger than the that of the monzonite granite in Ningshan batholith. The εNd values of both the magmatic and hydrothermal monazite range from -4.6 to -3.0, which is consistent with the εNd value range of the monzonite granite. This indicates the genetic relationship between the Be-Nb pegmatite and the monzonite granite. Based on various lines of evidence, this study concludes that the formation of Be-Nb rare-element pegmatites in the Ningshan district is the result of the residual magma crystallization of the co-genetic monzonite granite magma differentiation in the early stage in the Ningshan batholith.
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Large-scale autogenic stratigraphic mechanisms and Autostratigraphy

WANG Junhui, MUTO Tetsuji, XIAN Benzhong

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In response to external forcings such like eustatic changes, tectonic activities, and sediment supply, the stacking of strata is controlled by both autogenic and allogenic mechanisms. One of the main progresses in recent years is a realization that autogenic ones may take place in a wide variety of spatio-temporal scales during the deposition. Unlike small-scale autogenic mechanisms that happens on local positions of the depositional system, large-scale ones control the formation of strata regionally, which might modify and even change the allogenic processes. To check the relationship between strata stacking patterns and external forcings, large-scale autogenic processes must be determined from allogenic ones. Based on the understanding of large-scale autogenesis, autostratigraphy has developed in recent years. Autostratigraphy provides new perspectives in analyzing the relationships between strata stacking patterns and external forcings, based on two pairs of coupled notions, i.e. autogenesis and allogenesis, equilibrium and non-equilibrium responses. Autostratigraphy defines external forcings of constant rates as steady, and those of changing rates as unsteady. Strata stacking patterns or processes controlled by steady external forcings are considered as autogenesis, while by unsteady external forcings are considered as allogenesis. Autostratigraphy also defines steady strata stacking patterns or processes where the ratio of aggradation rate and progradation rate (i.e. Ragg/Rpro) remains constant during the interested period. Otherwise, the strata stacking patterns or processes are considered as unsteady. Equilibrium response is then defined as a response where steady external forcings form steady strata stacking patterns and thus is autogenic. If steady external forcings form unsteady strata stacking patterns, this response is called non-equilibrium response and is also autogenic. Moreover, unsteady external forcings may also form steady strata stacking patterns, which is also a kind of non-equilibrium response but is allogenic. Under the framework of autostratigraphy, the stacking up of strata generally takes the large-scale autogenic non-equilibrium responses and thus usually exhibits an unsteady pattern. In contrast, steady stacking patterns of strata only takes places under very rare conditions. The acquiescence of equilibrium response between strata stacking patterns and external forcings and its corollary in conventional genetic stratigraphy should be revisited.
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Characteristics of mylonite magnetic fabrics and constraint on the relationship between the shear zone deformation and mineralization

likang, jiaoqianqian

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Abstract：The Hetai goldfield with gold deposits strictly hosted by mylonite zones are considered to be a typical gold mineralization example related to ductile-shear deformation and have the largest gold reserves in Guangdong Province. However, the shear deformation conditions versus the gold mineralization remain unclear. The Gaocun and the Yunxi gold deposit confined to ML11 and ML9 mylonite zone respectively are the significant gold producers in the goldfield. The magnetic petrology and anisotropy of magnetism susceptibility (AMS) of the barren and auriferous mylonite in the shear zones were studied after the macroscopic deformation and petrography characteristic observation. The x-T curves of mylonite show the Curie temperature of pyrrhotite, in combination of the hysteresis loops, isothermal remanent magnetism (IRM) and petrography characteristics, indicating biotite and pyrrhotite are the dominated magnetic bearing minerals of the mylonite with no magnetite, the contribution of pyrrhotite much larger than the biotite in Hetai goldfield. Therefore, the AMS characteristics are effective to show the deformation of the shear zones. The barren mylonite in ML11 mylonite belt (Gaocun deposit) have the similar mean magnetism susceptibility value Km (＜500 μSI), corrected anisotropy degree Pj, ellipsoid shape factor T, magnetism foliation F and lineation L with the ML9 mylonite belt (Yunxi deposit). Moreover, both the shear zones show consistent orientation of principle stress, nearly horizontal NNW-SSE striking maximum principle stress σ1 (K3) and steep dip NEE-SWW striking minimum principle stress σ3 (K1). Kinematic vorticity of two shear zones are also undistinguishable, varying from 0.12 to 0.63, less than 0.71. These characteristics suggest that both the shear zones in the Hetai goldfield subjected to Indosinian NNW-SSE trending severe compression which resulted in the mylonite as the S and SL tectonites with intense oblate stain ellipsoid, and the pure shear is dominated in the shear deformation. However, the AMS characteristics of auriferous mylonite is distinct from the barren mylonite, with the Km and Pj value of the former larger than that of the later, suggesting that the mylonite deformation strength tend to have positive correlation with the gold mineralization. Consequently, In the shear zone, the stronger the ductile deformation and the steeper the dip angle of the maximum strain principal axes (magnetic lineation) of mylonite, the more favorable it is for brittle fracture and gold enrichment in the later stage.
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Late Quaternary activity and paleoearthquake recurrence characteristics of Litang Fault in Western Sichuan

zhangxianbing, Yangzhen, Zhongning, Yuhao, Guochangbao, Yangguifang, Lihaibing

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Active faults within the block have the ability to trigger large earthquakes of magnitude 7 or above, and their spatial distribution characteristics, activity, and seismic risk cannot be ignored. The Litang fault zone is an important seismogenic structure in the Litang area of the western Sichuan plateau, which is distributed within the Sichuan-Yunnan block. There are still different understandings about the formation age of surface fractures in the Litang Basin, the recurrence characteristics of paleoearthquakes, and the kinematic characteristics of the Litang Fault. Based on remote sensing interpretation, field geological survey, unmanned aerial vehicle photogrammetry, paleoseismic trench exploration, and 14C dating, this paper has determined the spatial geometric distribution, activity, and paleoseismic history of the Litang fault. The research results indicate that the surface fracture of the Litang Basin may be formed by the superposition of the 1948 Litang M71/4 earthquake and the 1729 Litang earthquake. The recurrence behavior of paleoearthquakes along the Litang fault conforms to the characteristics of cluster earthquakes, which is relatively similar to the recurrence characteristics of strong earthquakes along the Maoyaba fault, indicating that both fractures may occur simultaneously. The movement of the Litang fault is characterized by sinistral strike-slip with normal fault components, which is controlled not only by lateral extrusion movements on the southeastern margin of the Tibet Plateau, but also by differential movements of the Yajiang and Shangri-La secondary blocks. This study provides detailed information for understanding the seismic risk and tectonic deformation mechanism of active faults within the Sichuan-Yunnan block, as well as for planning, construction, and safe operation of major regional projects.
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A study on the crustal structure of the east-central Great Kinghan Range margin based on geophysical data fusion

Zhao WeiJun, Qin tao, Li JianPing, Xiao Feng, Han JiangTao, Rong Xing, Guo BaoDong, Ge Huan, Niu XingGuo

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Sitting in the east segment of Central Asian orogenic belt, Xing’an block and Songliao-Xilinhaote block were separated by the Hegenshan-Heihe suture. Likewise, Xingan block and Songliao block were separated by the Nenjiang Fault subsequently. In the central segment of the great Kinghan Range, these two structures overlap and is hardly to be distinguished. To investigate the important structures, divide the structure units, and determine the depth variation of the basement in the east margin of the great Kinghan Range, we have acquired a 60-km-length gravity, magnetic and magnetotelluric coincident profile in Zhalantun-Arongqi area, Inner Mongolia. The 1:20K Buguer gravity data in Zhanlan-Arongqi area were reprocessed. Through multiple geophysical fusion, seven important faults were inferred. Among them, the Pangjiajie Fault, the Hongxing Fault, and Alunhe Fault are deep faults, at least penetrating up to middle crust. In addition, two low-resistivity belts in the middle curst were revealed, among which, C2 anomaly is interpreted as Hegenshan-Heihe suture. geographically. By correlating with 1:25K geological mapping data, the geophysical interpretation results were proofed. The research outcomes are helpful to geological studies of crustal structures at the central-east great Kinghan Range margin. It has the significant implications for regional revolution history of the two blocks.
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Paleomagnetic Study of Early Cretaceous Red Beds from Wulian Section, Jiaolai Basin in Shandong Province and Its Tectonic Implications

Bao Jing, Hu Yu, Li Bingshuai, Yan Maodu, Liu Yongqing, Xu Kemin, Cui Mingming

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Understanding the Mesozoic vertical-axis rotation of the Jiaodong Peninsula is quite crucial to constrain the sinistral shearing of the Tan-Lu fault. However, there are still debates about whether rotation occurred, if yes, the rotation magnitude of the Jiaolai Basin during the Mesozoic. In this study, we conduct a detailed paleomagnetic study to the Early Cretaceous red beds of the Longwangzhuang formation at the Wulian locality in the southern Jiaolai Basin. Detailed rock magnetic results indicate that hematite is the main magnetic carrier, while pyrrhotite and magnetite as subordinate magnetic carriers in some samples. The Fisherian mean direction of the 8 sampling sites was Ds = 169.5°、Is = -33.2°、ks = 40.9、α95 =8.8, which was proposed to be the primary remanence acquired during deposition. The results indicate that the Wulian region underwent an obvious counterclockwise rotation of ~22.8±8.8° relative to the stable East Asia. Together with previous paleomagnetic results from the Jiaolai Basin, they probably indicate a holistic counterclockwise rotation of the Jiaolai Basin after the Late Cretaceous. Moreover, an increasing magnitude of counterclockwise rotation to the southwest along the Wulian fault was observed and most likely attributed to the increasing influence of the sinistral strike-slip faulting along the Tan-Lu fault to the west along the Wulian fault. There were different rotation senses and magnitudes in different periods along the Tan-Lu fault, which were not only influenced by the sinistral shearing of the Tan-Lu fault, but also related to the different nature and tectonic backgrounds of nearby blocks.
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The influence of deep fluid activities in the basin on the metallogenic process of sandstone type uranium deposits

YAN Zhaobin, ZHANG Wenwen, ZHANG Chengyong, XIA Fei, NIE Fengjun, WU Xiuyu

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Sandstone type uranium deposits have become the most important type of industrial uranium deposits in the world and China. Exploration and research have found that, there are not only supergene oxidation fluids but also deep fluids involved in some sandstone type uranium deposits. Therefore, it is very important to sort out and clarify the types of fluid activities in the deep basin and their relationship with sandstone-type uranium mineralization for carrying out "three new" (new areas, new horizons and new types) prospecting. In this paper, the present situation of deep fluid activities participating in sandstone-type uranium mineralization has been studied from the macro and micro aspects, combining with deposit examples, to explore its impact on uranium enrichment. The deep fluid activity in the basin is divided into three types: deep hydrocarbon fluid, magmatic volcanic hydrothermal fluid and deep formation water. The typical characteristics and identification marks of different types of fluid are summarized, and the time-space relationship between deep fluid activity and uranium mineralization is discussed; This paper expounds the change characteristics of uranium minerals, co-associated minerals, ore body morphology and physical properties of ore-bearing sandstone under the participation of deep fluid activities, and on this basis, discusses the interaction mechanism. The results show that the deep fluid activities mainly affect the formation of sandstone-type uranium deposits by providing new ore-forming materials and changing the ore-forming environment. The fluid and basin geothermal brine related to magmatic activity have a significant impact on the uranium source and temperature of mineralization, while the hydrocarbon-bearing deep fluid activity has a significant impact on the environmental conditions. Its significant reducibility can make up or strengthen the reduction ability of the formation, and form geochemical barriers or superimposed enrichment effects.There are obvious differences between the ore-forming process and mode of sandstone-type uranium deposits under the participation of deep fluid activities and the ore-forming process of shallow supergene oxidation fluid. As uranium exploration moves towards deep, it is necessary to strengthen the deepening and refinement research of the participation of deep fluid activities in uranium ore-forming process, enrich the ore-forming theory of sandstone-type uranium deposits, and promote the breakthrough of uranium exploration.
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Study on thorium enrichment process and spatial distribution in Baiyan Obo deposit

CHEN Biao, SUN Qing, SONG Wenlei, JIN Hailong, LI Qiang, WANG Qiwei, YANG Zhanfeng, JIA Xiaoqi, WEI Wei, LIU Yanjiang, PENG ZhangKuang, HOU Shaochun

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Bayan Obo deposit is a large Fe - REE polymetallic deposit with a large amount of thorium resources. However, iron and rare earth resources are the main minerals developed and utilized at present, while thorium resources are almost used up to now. It is an important basis for the development and utilization of thorium resources in the future to find out the occurrence state and distribution law of thorium resources in ore deposits and reveal the enrichment process and mechanism of thorium resources. In this paper, based on the results of systematic sampling, analysis and testing in recent years, detailed mineralogical observation and whole-rock chemical analysis were carried out on 570 samples from Baiyunebozhu, East and west mining areas. Independent thorium minerals, mainly silicorite, were identified in different types of ores. Silicorite, except a small amount of which were coated by rare earth minerals, usually interspersed in rare earth minerals in the form of veins. It shows the characteristics of lag enrichment. The average grade of ThO2 in the mining area is 0.0322 %, which is more than 30 times higher than the Clark value of the crust (9.6×10-4 %). There are obvious differences in ThO2 content among various ore types, and high ThO2 content is distributed in mica, amphibole, girine and fluorite ores. The low content of ThO2 in dolomite ore indicates that thorium mineralization is mainly formed in alkaline hydrothermal metasomatism and fluorination. In addition, thorium mineralization is enhanced with the increase of depth, which indicates that the deposit has good thorium ore-forming potential.
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Late Miocene—Pliocene Ostracoda Fauna of Tuolin Formation in Zanda Basin, Tibet

chenfenning, chenruiming, Lina, Songbowen, Zhangkexin, Xuyadong, Zhaxianfeng

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The Cenozoic strata of the Zanda Basin in southern Tibet have yielded abundant Ostracoda fossils. Two Ostracoda assemblages have been established based on the distribution patterns of Ostracoda fauna on the stratigraphic profile: (1) Ilycocypris bradyi - Cyclocypris orum - Leucocythere dorsotuberosa assemblage; and (2) Leucocytherella-Candoniella zadaensis-Leucocythere mirabilis assemblage.Through comparison of the ostracod assemblages of the study area with those found worldwide at the same stratum, the age of the Tuolin Formation in Zanda Basin has been redefined to late Miocene to Pliocene.Based on the distribution characteristics of the fossil succession, the Ostracoda fauna in the study area has been be divided into seven ostracod communities in ascending order: Candona -Candoniella community; Ilycopris-Cyclocypris community; Leucocythere-Candona community; Ilycopris-Leucocythere community; Leucocythere-Leucocytherella-Candona community; Leucocythere mirabilis-Candona community and Ilycopris -Leucocytherella community. Through detailed character analysis of ostracod communities and the magnetostratigraphic chronological data, the paleoclimate of the Zanda Basin during 9.5~1.7 Ma was divided into six periods: 1) the cool and wet period (9.5-8.4 Ma); 2) the warm and humid period (8.4-6.3 Ma); 3) the cool and wet period (6.3-5.5 Ma); 4) the warm and humid period (5.5-4.4 Ma); 5) the cold and wet period (4.4-2.8 Ma); and 6) the warm and dry period (2.8-1.7 Ma).. Through a comparison of the climate evolution characteristics of the study area with the global climate evolution since 9.5 Ma, it is postulated that the Zanda Basin experienced primarily warm and humid conditions between 9.5 and 6.3 Ma, likely related to the strengthening of the southeast monsoon from India. The paleoclimate analysis of the Zanda basin during the interval 6.3-3.6 Ma indicates a period of relatively warm and humid, with climate fluctuations, possibly due to the re- strengthening of the southeast monsoon from the Indian Ocean. Subsequently, after 3.6 Ma, the influence of the global climate cooling, winter monsoon strengthening, and the strong uplift of the Qinghai Tibet Plateau caused a shift towards a cold and dry environment in the Zanda Basin. However, the area experienced a transition to a warm and humid climate between 2.8 and 1.7 Ma.
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Provenance and Tectonic Setting of the Lower Carboniferous in West Section of North Qaidam Basin: Constraints from Detrital Zircon U-Pb Geochronology and Geochemistry

HUJUNJIE, SHIHUI, MALICHENG, MAYINSHENG, lizongxing, WANGJIAQI, ZHONGCHANG

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Aiming at finding out the material source and tectonic background of Early Carboniferous strata in west section of northern Qaidam Basin. In this study, the Huaitoutala Formation clastic rocks from Xiaosaishiteng Mountain area were collected for geochemical and detrital zircon U-Pb geochronology analysis. The results show that UCC-normalized trace element spider diagram of clastic sedimentary rocks is flat shaped, with the enrichment of Th, U, Hf and the loss of Co, Sc, Ni, V. The rare earth elements of the sandstones display obvious fractionation in light and heavy REE, strong enrichment in light REEs with medium negative Eu anomaly. The Cr/Zr, Sm/Nd, Th/Sc and Th/U ratios and discrimination diagrams indicating that most sediments were derived from upper crust source area with felsic- intermediate rocks as dominant contributors. Multiple geochemical parameters revealed the geochemical characteristics of test samples are close to the continental island arc sandstone. Interrelated tectonic environment discrimination also verified that Huaitoutala Formation was developed in continental island arc and active continental margin tectonic settings. The U-Pb ages of detrital zircons in Huaitoutala Formation can be divided into three populations: 401～480 Ma, 900～1493 Ma and 1803～1908 Ma, which yield a single Early Paleozoic peak (414 Ma) in histogram, indicating key tectonomagmatism episodes of the north Qaidam Caledonian Orogenic Belt during late Early Paleozoic. Based on previous research conclusions of paleogeography and paleocurrent evidence, it is inferred that the provenance of the Early Carboniferous Huaitoutala Formation have come from the north Qaidam Caledonian Orogenic Belt.
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Restudy on the Cranium of the Early Triassic Hupehsuchus nanchangensis ( Diapsida: Hupehsuchia)

Zhao Bi, Zou Yarui, Li Jiangli

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Hupehsuchus nanchangensis is the most representative species in the Nanzhang-Yuanan Fauna and one of the oldest marine reptiles. The information about the key features of its cranium is very scarce. Therefore, in order to supplement this part of the content, a fossil specimen collected recently has been carefully repaired and studied in comparative anatomy. This study revised the following cranial diagnoses of this species: a narrow bone space along the middle line of the skull develops along the two branches of upper jaws; the premaxilla contacts with each other at the anterior end, while the nasal only contacts at the posterior ends; groove develops on the premaxilla in the same direction as that of the maxilla; top of the skull is flat without sagittal crest; the parietal is larger than the frontal, and the pineal foramen is located in the anteromiddle part of the parietal; upper temporal fenestra is formed by parietal, postfrontal, postorbital and squamosal, excluding supratemporal; its jugal is a triradiate bone with a thin and long anterior process, and a short ventral process; supraoccipital is large and nearly round; exoccipital has clearly visible nerve opening. The comparision shows that Hupehsuchus nanchangensis, Nanchangosaurus and Eretmorhipis all bear bone spaces formed by both sides of upper jaws, which might be the homologous character of Hupehsuchia. The supratemporal of Hupehsuchus nanchangensis does not participate the upper temporal fenestra. In addition, this species has morphological vestiges of the ventral process of jugal and its inferior temporal fenestra is not completely degraded, which is similar to the oldest diapsid reptiles, but different from the advanced ichthyosauromorphs. It is speculated that with the development and evolution, ichthyosauromorph supratemporal gradually moved forward and participated the upper temporal fenestra, while the inferior temporary fenestra gradually closed. The new material also shows that the external naris of Hupehsuchus nanchangensis is upward and its bite force is not strong, so it can be inferred that this species has a unique feeding function different from other species of ichthyosauromorphs.
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Ductile deformation of Wenchuan-Maoxian fault constrain the early uplift of Longmen Shan

GE Chenglong, LI Haibing, Philippe Hervé Leloup, ZHENG Yong, Liu Dongliang, ZHANG Lei, YE Xiaozhou, Thomas Courrier, ZHANG Jinjiang

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Wenchuan-Maoxian fault in the eastern margin of the Tibetan Plateau (Longmen Shan) is the major fault that has developed deep ductile deformation and played an important role in controlling the early uplift of the Longmen Shan. By using the field survey, macro/micro structure analysis, and crystal fabric analysis, we have constrained the kinematic and rheological characteristics and deformation conditions of ductile deformation of the Wenchuan-Maoxian fault. The results show that (1) ductile shear zone approximately 3 km wide and steeply dipping to the north west exists within the fault; (2) two phases of deformation are identified within the shear zone: early Top-to-NW normal shearing and late Top-to-E reverse shearing; (3) The quartz CPO results show that the reverse ductile deformation is dominated by basal slip, accompanied by bulging recrystallization, with an indicated deformation temperature of 300 - 400℃. The normal ductile deformation is dominated by prism slip, accompanied by subgrain rotation recrystallization, with a corresponding temperature of 350 - 650℃. Combining with published geochronological and thermochronological data, we suggest that the Wenchuan-Maoxian fault underwent Top-to-NW normal ductile faulting in the Oligocene and Top-to-E reverse ductile deformation in the Miocene, which resulted in the uplift and exhumation of large amounts of deep material in the hinterland region of Longmen Shan.
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Ostracod records from drill core in the Qarhan and its denotation for Late Pleistocene high lake level in Paleo-lake Qarhan

songbowen, Ke Xue, Song taizhong, Zhang kexin, Yang wenjun, Zhang jinming, Zhang xiaojin

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The Qarhan Salt Lake is the depocentre of the Qaidam Basin during the Quaternary, with a very thick sequence of lacustrine sediments. Continuous lacustrine sediments provide excellent archives of detailed paleo-environmental data regarding climatic change in the Qaidam Basin and northern Tibetan Plateau. In this study, fossil ostracods from the drill core (ZK53630-1) sediment were analyzed in conjunction with AMS 14C dating. A total of 10 ostracod species belonging to 7 genera are identified. The ostracod fauna can be subdivided into two assemblages from bottom to top: Ilyocypris biplicata– Limnocythere inopinata and Ilyocypris bradyi – Ilyocypris sebeiensis. The ostracod fauna and associated micro-fossils suggest the existence of a large freshwater to oligohaline lake in the Qarhan area during Late Pleistocene (MIS 3a, 34–28 ka), coeval with a warm and humid climate, which was completely different from the present-day hyper-arid salt lake environment.
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Gold mineralization of the Woxi Au-Sb-W deposit in Hunan Province: based on element-geochemical features and thermodynamic modelling analysis of native gold

Liang Yi, Ge Hang Fei, Wang Guo Gang, Pei Qiu Ming, Hoshino Kenichi

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The Woxi Au-Sb-W deposit, located in the Jiangnan orogenic belt, represents a typical case where W, Sb, and Au mineralization occur within a large-scaled single deposit. The native gold produced in the Woxi deposit is characterized by extremely high gold fineness (>998). This paper, focused on the gold mineralization, uses ICP-MS analysis and microthermometric analysis of fluid inclusions to determine geochemical features in mineralogy and characteristics of ore-forming fluids, and investigates the indication of gold fineness and Au/Ag ratios for the gold mineralization. The ICP-MS analysis shows Au/Ag ratios are higher in scheelite (103-520) and pyrite (69-673) and lower in stibnite (6-65) and host rocks (0.3-35), while Au/Ag ratios are varied in a large range in quartz (6-199). Based on results of the microthermometric analysis (200~350℃), this paper uses thermodynamic modelling to simulate ore-forming fluids of the native gold associated with pyrite and sericite, showing that the gold solubility is easier to be decreased by the sulfur concentration than the temperature, and the gold fineness has a positive correlation with the temperature and a negative correlation with the sulfur concentration. The native gold in the Woxi deposit is more likely to precipitate in the fluid with a higher temperature and a lower sulfur concentration, thus associated with pyrite and scheelite. This paper is expected to provide a new method to study other gold deposits.
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Geological characteristics of Early Permian Baliklik Formation reefs at the south Kezilblak Gully in the northwest margin of the Tarim Basin

Wang Yijun, Yang Guang, Wang, Tang Hongming, Zhang Yunfeng, Qu Haizhou

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At the Permian Baliklik Formation in the northwest margin of the Tarim Basin, there developed massively thick reef limestone that bears oil and gas exploration significance. This paper makes macro and micro examinations of the reefs which cropped out at Kizilbulak Nangou in the northwest margin of the Tarim Basin. This set of reefs had bioclastic shoals as reef bases. The lower zone of the reef core is mainly composed of microbialite of various types formed by Cyanobacteria, with thrombolite and broken-up microclots as its most dominant structural components, followed by stromatolites. At this time, the hydraulic energy is low. In the upper zone of the reef core locally developed phylloid algal reefs, with a large quantity of marine benthic fauna among them. At this time, the reef body began to expose itself above the wave base, with a large number of brecciated limestone developed, and it was subjected to the transformation of atmospheric freshwater karstification. In addition to the platform margin zone, the synchronous restricted platform in the Keping area in the northwest Tarim Basin also developed small-scale intra-platform reef-shoal complexes, with microbial rock characteristics, indicating that the environmental conditions in the region during this period were generally favorable for reef building. The set of reef-shoal complexes in the Baliklik Formation formed in the late Atherian period of the Early Permian to the Sakmarian Age, contemporary with the early stage of large igneous provinces of Early Permian Tarim Basin. Therefore, it is speculated that the forming of this set of reef-shoal complexes was related to the "eutrophication" of the sea water in the residual basin of the South Tianshan Ocean; the “eutrophication” had been caused by the volcanic ash spurted out by volcanic activities at that time. As a result of the outbreak of algae, the δ13C value of the reef-shoal complexes in the Baliklik Formation shows a significant positive shift compared with that of the carbonate rocks in the Kangkelin Formation. However, the reef-shoal complexes of the Baliklik Formation was much transformed by cementation and other constructive types of diagenesis, unfavorable to the forming of reservoirs. In other words, the reef-shoal complexes of the Baliklik Formation in the region, despite their desirable facies belts, possess poor reservoir permeability; high permeability layers only developed where structural fractures occurred. Therefore, it can be theorized that reef-shoal reservoirs of the Early Permian Baliklik Formation in the northwest margin of the Tarim Basin are, generally speaking, not controlled by facies, and that fractured reservoirs were dominant. Thereupon, exploration of Permian reef-shoal oil and gas reservoirs in the northwest margin of the Tarim Basin should focus on the structural fractured members. In brief, this study is an attempt to provide some scientific basis for the prediction of high-quality reservoirs in the Baliklik Formation reefs of the Tarim Basin, and to promote further research into Permian microbial rocks in China and throughout the world.
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Strata missing of the Ediacaran upper Dengying Formation at the northwestern Mianyang-Changning intracratonic sag, and tectonic implications

Dingyi, Liu Shugen, Wen Long, Ma Kui, Chen Daizhao, Song Jinming, Wang Han, Wang Linkang, Chen Mingsi, Yang Bo, Tang Pan, Li Zhiwu

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Although it is well accepted that the Mianyang-Changning intracratonic sag plays an important role in petroleum accumulation, its spatio-temporal distribution and formation mechanism are still controversy. In this case, this study carries out systematic stratigraphy and lithofacies investigations on the Sinian-Cambrian successions of the Guangyuan-Ningqiang area, at the northeastern margin of the Mianyang-Changning intracratonic sag. The lithofacies indicators and biostratigraphy suggest that the lower Beiwan Member or upper Algal dolomite Member are commonly overlain by Kuanchuanpu Formation, and thus the Gaojiashan and Beiwan members are pervasively missing at Kuanchuanpu, Shujiaba and Caojiaba-Dongshanzi areas. This indicates that the strata missing of the upper Dengying Formation at eastern margin of the Mianyang-Changning intracratonic sag can extend from the Central Sichuan Basin and north slope of Central Sichuan Paleouplift to the Guangyuan-Ningqiang area. The sharp shift from tidal flat-lagoonal microbial dolomite and dolomudstone in the study area to slope-basinal chert at Datan-Yangmu area indicates the control of extensional fault. Similar sharp shift in facies is also present at the southern margin of middle Yangtze platform and eastern margin of the upper Yangtze platform, reflecting an extensional tectonic regime with the formation of fault-bounded carbonate platforms. The width of several kilometres, erosion thickness of hundreds of metres and the depositional break up to 20 Myr suggest that Mianyang-Changning intracratonic sag can be attributed to differential subsidence/uplift rather than karstic morphology. The linear distribution of strata missing area at eastern margin of the Mianyang-Changning intracratonic sag should be resulted from relative uplift at the tilted block. The climax of extensional faulting occurred at the Sinian-Cambrian transition, causing the strata missing of the upper Dengying Formation to the lowermost Kuanchuanpu Formation.
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Tectonics and discrepant evolution of Cenozoic sedimentary basins adjacent Hainan Island

Wu Shiguo, Long Genyuan, Lu Xiangyang, Li Gang

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The four Cenozoic sedimentary basins have been developed adjacent Hainan Island, these are Yingehai basin, Beibuwan basin, Qiongdongnan basin and Zhu III sag of the Zhujiangkou basin. Based on the latest geophysical data, we have redefined the Mesozoic Cenozoic basin structure and basin evolution as well as its relation to Hainan onshore geological structures. The basins have well developed the NE and NW structures, but existed the great difference. Influenced by Red River fault, former NW trending Yinggehai basin is characterized by tension and compressive torsion of pull apart basin. Whereas the NE basins located in the southern of the continental margin of South China, sandwiched between Jiangshao-Bobai Faults and the southern of Lishui-Nanao faults. The evolution of the Baisha basin is consistent with the Mesozoic basin of the continental margin of South China. The extension began in the Late Cretaceous, with four rifting. The later magma reconstruct the sedimentary basin, showing magma eruption and high heat flow value. This tectonic distribution is extremely incompatible with the surrounding basins. The offshore fracture could extend to southernmost, showing obvious seismic activity. We inferred that the tectonics of Hainan Island has consistency with northern South China Sea margin.
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Petrogenesis of the high-pressure mafic granulite in the Eastern Himalayan Syntaxis and its tectonic implications

wu shuangpeng, zhang zeming, tian zuolin, lu weirui, guo mingming, zhang chengyuan

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There are typical high-pressure pelitic, felsic, and mafic granulites in the Namche Barwa Complex in the Eastern Himalayan Syntaxis. However, the distribution and spatial variation of metamorphic conditions and times of the high-pressure granulites in the Namche Barwa complex need to be further studied. In this paper, we conducted a petrological and geochronological study for high-pressure mafic granulite from the Baga area in the southwest segment of the Namche Barwa Complex. The high-pressure mafic granulite consists of garnet, amphibole, clinopyroxene, plagioclase, biotite, and quartz, and the porphyroblastic garnets show growth compositional zoning. The granulite contain three stages of mineral assemblage: the prograde one is the core of porphyroblastic garnet and hosting mineral inclusions, including garnet, quartz, titanite, and apatite; the peak metamorphic assemblage is the rim of porphyroblastic garnet and matrix minerals of clinopyroxene, plagioclase, amphibole, quartz, rutile, and melt; the retrograde assemblage is symplectitic and matrix minerals, including clinopyroxene, amphibole, plagioclase, biotite, quartz, and titanite. The high-pressure granulite has a clockwise P-T path, with peak metamorphic conditions of 1.5 GPa and 915 ℃ and ~26 vol% partial melt under the peak condition. The retrograde metamorphism and melt crystallization of the granulite is likely to occur at ~26 Ma, and last until ~14 Ma. Combined with previous studies, we suggest that the high-pressure granulites in the Namche Barwa Complex have a wide spatial distribution, extending at least more than 80km from the northeast Gala, Zhibai, Pai to the southwest Baga area, and that these granulites have similar metamorphic conditions and metamorphic timescale. This study indicates that a large number of high-pressure granulites in the Namche Barwa Complex were derived from high-temperature and high-pressure metamorphism and partial melting of the underthrusted Indian continental crust, representing the thickened lower crust of Himalayan orogen, the voluminous melts produced by intensive partial melting of the high-pressure granulites provide the sources for the Himalayan granites.
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Trace element composition characteristics of sphalerite in the Pusangguo cobalt-rich Cu–Pb–Zn deposit in Tibet and its indicative significance

Li Zhuang, Lang Xinghai, Liu Hui, Zhan Hongyu, Tan Hao, Zhang Peng

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The Gangdese metallogenic belt (GMB) in Tibet, located in the East Tethys metallogenic domain, is one of the famous Pb, Zn and other nonferrous metal areas in China. The Pusangguo is a large newly discovered cobalt-rich Cu–Pb–Zn deposit in recent years. The ore bodies mainly occurred in the contact zone between the magma and the Early Cretaceous Takena Formation strata, with the complex mineralization. Sphalerite is one of the main sulfides in the quartz-sulfides mineralization stage in the Pushangguo deposit. It mainly contains two different types: dark-brown type I sphalerite (SpI) and light-brown type II sphalerite (SpII). In this paper, the electron microprobe analysis (EMPA) and laser ablation inductively coupled plasma mass spectrometer (LA-ICP-MS) were used to analyze the trace elements in sphalerites. The results show that the sphalerite is generally rich in Co, and the content of Co in SpI is obviously higher than that in SpII. Co mainly replaces Zn element (Co) in the form of isomorphism Co2+? Zn2+; Both SpI and SpII are characterized by enrichment of Fe, Mn, Cd and depletion of Ga, Ge, In, among which Fe, Mn, Cd and other elements occur mainly in the form of isomorphism, while Cu, Ag, Pb, As and other elements occur mainly in sphalerite in the form of mineral inclusions. According to the correlation between different trace elements, it is considered that there may be Fe2++Mn2+?2Zn2+、(In3+, Sn3+)+(Cu+, Ag+)?2Zn2+、As3++Ag+?2Zn2+、Pb2++2As3++□?4Zn2+ (□is lattice vacancy) and other simple complex element substitution mechanisms. The ratios of Fe, Mn, Ge, In/Ga, In/Ge, Zn/Cd in sphalerite and the calculation results based on the sphalerite GGIMPis geothermometer indicate that sphalerite was formed in the environment of medium-high temperature (237~345℃), low oxygen fugacity and low sulfur fugacity (logf(S2)=-13.4~-8.3).
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The deposit types, spatial and temporal distribution and prospecting direction of rare earth deposits in China

Yu Jinjie, Chen Shaocong, Chen Xiaodan

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Rare earth element (REE) deposits in China can be categorized into the hard rock-type, ion adsorption-type, and placer REE deposits. The hard rock-type, ion adsorption-type, and placer REE deposits account for 96.4%, 3.2% and 0.5% of the total REE resource of China, respectively. The REE deposits in China are composed of 12 metallogenic zones, and the peak periods of mineralization are mesoproterozoic and Cenozoic. The former is represented by Bayan Obo ore deposit, while the latter is represented by the REE deposits of the Mianing-Dechang metallogenic zone and ion adsorption-type REE deposits in six provinces of southern China. The available rare earth deposits in China are carbonatite and alkaline rock-related and ion adsorption type REE deposits. The former is the source of LREE and the latter is the source of HREE. The controlling factors of carbonatite and alkaline rock-related REE deposits include rifts or collision-post-collision tectonic settings along craton margins, regional deep faults, and the magmas and post-magma hydrothermal evolution. The controlling factors of ion adsorption-type REE deposits include parent rocks, favorable exogenetic factors including quasi-equilibrium between denudation and exhumation at regional scales, local geomorphology dominated by low-lying gentle slopes, adequate rainfall, and favorable groundwater conditions. In this paper, the general metallogenic models of carbonatite and alkaline rock-type and ion adsorption-type REE deposits are recommended. The prospecting of carbonate rock and alkaline rock-type REE deposits Sis concentrated in the depth and edges of known deposits, but the search for hard rock-type heavy rare earth deposit in Xingmeng and Boziguer-Yilanlik metallogenic belts should not be ignored. Southern Jiangxi and northern Guangdong provinces are the key areas to search for ion adsorption-type HREE deposits.
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Ocean－continent transition process in the West Junggar tectonic belt: constraints from the basalts of the Baiyanghe Formation

LI Yongjun, ZHANG Jianye), YANG Gaoxue, DUAN fenghao), LI Wei)

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West Junggar structural zone distributed in the south western of the Central Asian Orogenic Belt, It’s a key area for studying the evolution of the Paleo Asian Ocean. However, there are currently controversies over the tectonic evolution of the West Junggar tectonic zone in late Carboniferous. The newly discovered volcanic rocks from the Baiyanghe Formation in Early Permian probably can alleviate those controversies. Baiyanghe Formation volcanic rocks are mainly consist of basalts and the symbiotic subvolcanic rocks. It has angular unconformity relationship on the Early Permian Jiamuhe Formation with continental molasse sequence. In terms of geochemical compositions, the basalts are relatively high concentrations of Al2O3 and low concentrations of TiO2, they belong to the middle－low K calc-alkaline series. The ratio of ∑LREE/∑HREE ranges from 2.31 to 5.00. All the basalts of the Baiyanghe Formation are enriched in LREE without obviously Eu anomaly (δEu=0.99～1.29). Furthermore, they are enriched in light LILE, such as Ba, K, Sr. In addition, depleted in HFSE such as Nb, Ta, Zr, Hf and show the “TNT” negative anomaly. (206Pb/204Pb)i =17.924～18.000, (207Pb/204Pb)i =15.469～15.509, (208Pb/204Pb)i =37.737～37.879. εNd(t) = +5.93～+6.76, 87Sr/86Sr =0.703974～0.704299, It indicates that the source probably is the dehydration of subducted plate to produce the fluid result in metasomatic depleted mantle. These characteristics are consonant with the geochemical characteristics of late carboniferous marine island arc basalts, they have correlation in timeliness and extensity, and have the characteristics of homology, syngenesis and syntectonic background, it seems like excellent inheritance. The time of Baiyanghe Formation later than Jiamuhe Formation molasse, which confirms that Baiyanghe Formation basalts were erupted after the closure of the ocean basin, so it belongs to “Lagged arc” formation. Combining with previous researches and the regional geological background, the ocean basin was closed in Late Carboniferous, nevertheless, the deeply subduction continued until produced the Baiyanghe Formation in Early Permian. In the process of ocean-continent transition, it experienced a unique tectonic evolution process of “Lagged arc”. The “Lagged arc” formation volcanic rocks provide essential constraints for the suture location of the Paleo-Asian Ocean and the tectonic evolution process in West Junggar.
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Deep structure and genesis of Sanmenxia fault basin and its adjacent area ——Evidence from deep seismic reflection and magnetotelluric sounding

He Faqi, Yu Wenhui

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In recent years, a lot of work has been done on the oil, gas and geothermal resources in the Sanmenxia faulted basin, but the genetic mechanism is less studied, which seriously restricts the exploration and exploitation of mineral resources. On the basis of previous research, combined with field geological survey and the use of high -precision deep reflections seismic profile, magnetotelluric (MT), gravity and magnetic geophysical exploration technology, Sanmenxia Basin comprehensive study. It is found that the Sanmenxia Basin is mainly composed of two negative flower-like structures in the east and west, and the west flower-like structure is larger than the east flower-like structure. The eastern edge of the basin is adjacent to the Luoyang Depression and the Guanyintang uplift. The Guanyintang uplift has a lens-like low-velocity body in shell, and large scale hidden reverse faults are developed on the east and west sides of the uplift. The Moho surface in the study area is a detachment layer with a thickness of about 5 km, which shows earthworm reflection characteristics on the deep reflection seismic profile, indicating that the detachment layer moves westward. Several new arc-shaped faults were found in the upper and lower parts of the Moho detachment layer. The comprehensive study of geological and geophysical data shows that the decoupling of the Moho detachment layer is the main reason for the formation of the flower structure in the Sanmenxia fault depression basin. Under the action of different temporal and spatial tectonic forces, the Cenozoic whole crust rotating floral tectonic basin was formed in the study area.
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Mechanism of mineral precipitatiaon and genesis of the Shagou Ag-Pb-Zn deposit in the eastern Qinling metallogenic belt, China

Jinhong Xu, Chengquan Wu, Zhengwei Zhang, Yanwen Tang, Yuping Jiang, Shuli Hu, Chaofei Zheng, Xiyao Li, Ziru Jin

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Several vein-like silver polymetallic deposits are developed in the eastern Qinling metallogenic belt, among which the Shagou large Ag-Pb-Zn deposit commonly contain authomorphic quartz grains coeval with sulfides, which record important information on the physical-chemical conditions of different mineralization stages and metal mineral precipitation from ore-forming fluids, and provide a good opportunity to reveal mineral precipitation mechanisms and deposit genesis. In this paper, a fine mineralogical study of quartz in the Shagou deposit was carried out by cathodoluminescence, fluid inclusion microcalorimetry and individual fluid inclusion composition analysis based on detailed field geological investigations. Three stages of mineralization can be identified based on mineral assemblages: (1) quartz(Q1)-siderite-pyrite stage, Q1 is located in the core of quartz grains, and is characterized by uniform bright cathodeluminescence (CL) intensity with undeveloped growth zonings, representing pre-ore; (2) quartz(Q2)-dolomite-polymetallic sulfide stage, Q2 is located in the mantle of quartz grains, and coeval with sulfides, and is characterized by dark CL intensity with chaotic growth zonings, representing the metallogenic stage; (3) quartz(Q3)-calcite stage, Q3 is located in the edge of quartz grains, and is characterized by bright CL intensity with good growth rings, representing the post-ore stage. The compositional analysis of quartz from various stages showed that a significant positive correlation between Al and Li in quartz at all stages (R2=0.97) and a close correlation with the cathodoluminescence brightness, indicating that Al3+ and Li+ replace Si4+ into quartz. The Ti content of Q1 and Q2 ranges from 0.722 to 3.62 ppm and 0.387 to 1.12 ppm, respectively, and the Al content ranges from 81.9 to 2436 ppm and 3.67-132 ppm, indicating that the mineralization system is a medium-low temperature, medium-alkaline hydrothermal environment, with decreasing temperature and increasing pH being the main factors triggering mineral precipitation. The compositional analysis of single fluid inclusion by LA-ICP-MS shows that the mineralizing fluid is enriched in alkali metals with high Rb/Na and Cs/Na ratios, indicating that the Shagou deposit is related to magmatism. Comprehensive studies suggest that the Shagou deposit is characterized by multi-stage hydrothermal mineralization and is identified as a distal product of a magmatic-hydrothermal mineralization system, which is indicative of the exploration for hidden porphyry-type Mo(W) deposits.
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Comparison of serpentinization in different tectonic environments: A case study of the Tianshan and North Qilian orogenic belts in Southwest China

Yao Yongxiang, Xiao Yuanyuan, Lin Jinyan, Wu Shengying

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Serpentine, with a water content of about 13%, is an important hydrated mineral on the earth and widely distributed in different tectonic environments, e.g., the ocean floor, subduction zones and fore-arcs. Except fluids, fluid-mobile elements (B, Li, As, Sb, Pb, Cs, U, Sr, Ba) can be also enriched in serpentine with serpentinization. Thus, serpentine can be present as the important host for fluids and these elements in different geological processes. However, different tectonic environments have varying temperatures and pressures with potentially different properties of fluids. Serpentinization in different environments cannot only result in the formation of different serpentines (e.g., lizardite, antigorite), but may also lead to different enriched characteristics of serpentine, which require further studies. Based on comparison of compiled literature data for serpentinite produced in different tectonic environments worldwide, together with the serpentinite samples from two typical orogenic belts of Southwest Tianshan and Qilian Mountains, we found that abyssal serpentinite and serpentinite in subduction zones show different enriched characteristics of B, Ba and Cs : (1) abyssal serpentinite has significantly higher B contents, which may reflect the preference of B to serpentinite at lower temperature; (2) Ba and Cs contents of serpentinite formed in subduction zones are relatively higher, which may indicate tbe contribution of subducting sediments. This conclusion is helpful for interpreting the tectonic environment for serpentinite through its compositional characteristics.
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Response of Carnian Pluvial Episode in southern Ordos Basin

Li Jianguo, Wei Yi, Yang Bing, Lei Xiaoting

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In order to study the response of the Carnian Pluvial Episode in the southern Ordos Basin, pollen fossils, organic carbon isotopes, framboid pyrites and major elements were analyzed in Yanchang Formation in the core ZH2. Two pollen assemblages are divided as (I) Punctatisporites- Verrucosisporites-Osmundacidites assemblage and (II)Asseretospora- Apiculatisporis assemblage from bottom to top. The geological dates are the Middle Triassic Latina and the late Triassic Carnian. In the Zhangjiatan shale in lower part of the pollen assemblage (II), the total organic carbon is enriched and the organic carbon isotope has a negative drift of 4.88‰. Meanwhile, the framboid pyrites index indicates that this layer was formed in anoxia environment, and the Al2O3/MgO and CIA value are high values in this layers, indicating a high temperature, humid and enhanced weathering environment. These characteristics indicate that the Carnian Pluvial Episode had a significant impact on the Ordos Basin. Further analysis shows that these indicators can be divided into four independent high temperature, humid, anoxic and organic carbon enriched fragments in the Zhangjiatan shale, indicating four climatic fluctuations of the Carnian Pluvial Episode in the Ordos Basin, named as CPEⅠ、CPEⅡ、CPEⅢ、CPEⅣ.
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Sedimentary characteristics of Devonian/Carboniferous boundary in Northeastern Guangxi and the implications for the evolution of platform-basin alternation

WU Liangjun, WANG Pujun, WU Jiwen, WEI Shengliang, Hu Jingsong, LV Yong, PAN Ming, ZHOU Jiaming, LIN Yu, LIAO Jiafei, LI Xilin, SU Guangyang

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Platform-basin alternation is an important feature of Devonian and Carboniferous sedimentation in Northeast Guangxi, and the D/C boundary is one of the most prominent periods of this feature. This paper reviews the research history, facies division and representative sections of D/C boundary in Northeast Guangxi. The D/C boundary can be divided into the clastic rock facies, the carbonate rock facies and their transition type’s facies. Through the comparison of lithologic characteristics of 20 sections, the lithofacies palaeogeography of relative decline period of sea level of D/C boundary in Northeast Guangxi has been restored. The results show that in this period, there were two major platforms in Liuzhou and Guilin area and several small platforms in other place. Deep water sediments with rapid facies transformation are well developed among platforms. In the upper D/C boundary (early Carboniferous), the distribution of platform facies are significantly expanded, the supply of the South Yangtze River ancient land was enhanced, while the degree of facies transformations are increasing. This led to the pattern of platform-basin alternation is enhanced. In order to further explore the evolution process and the controlling factors of sedimentation behind the D/C boundary in Northeast Guangxi, this paper discusses the stages of the platform-basin alternation evolution, the influence of the synsedimentary tectonism and the sea level changes. And the relationship between sea level and tectonic movement has been combed. It is considered that under the premise of continuous faulting of Yunnan Guizhou Guangxi rift basin, the main reason for the sedimentary division of D/C boundary in Northeast Guangxi may be the abnormal fluctuation of sea level caused by the Gondwana glaciers. And the local synsedimentary fault depression increasing caused by Liujiang movement intensifies the sedimentary differentiation. The coupling effect of tectonic and sedimentary factors reached the strongest at the D/C boundary, and finally promoted the platform-basin alternate pattern in Northeast Guangxi to reach its peak at this period. In this model, the evolution of platform-basin alternation can be divided into 4 stages in Northeast Guangxi. The middle-late period of Early Devonian was the bedding stage of the platform-basin alternating pattern. The late period of Early Devonian to late period of Middle Devonian is the development stage while sedimentary facies began to differentiate. The Late Devonian to Early Carboniferous was the prosperity stage, the abnormal decline of sea level and the Liujiang movement began to act on the sedimentation. After the Carboniferous, the platform basin-alternating deposition maintained the intensity, and the seawater gradually returned to normal in the late period of Early Carboniferous, the basin-alternating pattern gradually weakened.
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The Present-day strain characteristics and dynamic mechanism around the Eastern Himalayan Syntaxis revealed by the latest GPS data

Wei Shaogang, Xu XiWei, Wu Yanqiang, Liang Shiming, Luo Jiahong

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The Eastern Himalayan Syntaxis (EHS) and its vicinities, located in the tectonic front of the collision between India plate and Eurasia plate, is characterized by strong crustal shortening and tectonic rotation deformation. Based on the latest and large-scale GPS velocity data, we analyze horizontal differential crustal movement associated with the EHS and its vicinities. Furthermore, we use a ‘‘spline in tension’’ technique to get a continuous strain rate map of the EHS region. Combined with the previous research results, we focus on the present-day tectonic deformation and mechanism of the EHS and its vicinities, and try to discuss the continental internal dynamic mechanism reflected by the current tectonic deformation in this area. The following results are obtained: Under the background of continuous subduction of Indian plate beneath Eurasian plate at an angle of NE20°, the most remarkable crustal motion is the clockwise rotation of southeastern and eastern Tibetan Plateau around the Eastern Himalayan Syntaxis. The maximum rotation rates of (109.7~123.6) × 10^-9 rad/a occurred to the east of the Syntaxis, around this area of Lancangjiang fault, Jinshajiang fault and Nujiang fault. High value region of tectonic strain rates in this area concentrate around the vicinity of Himalayan Main boundary thrust, Sagaing fault, Xianshuihe-Xiaojiang fault and other large strike-slip faults, as well as the ring areas of the Eastern Himalayan Syntaxis, whereas there are no significant strain anomalies in the area across Jiali fault and Red-River fault. Moreover, the maximum superficial compressive strain rates of 152.1×10-9/a is in the northeast areas of Assam sub-block, which indicates that the core position moves from the Namjagbarwa area towards its southeast to the northeast of Assam, where the Himalayan Main boundary thrust successively meets the inferred Northern Sagaing thrust. It is considered according to the research that, owing to the hyper-oblique subduction of the Indian plate, the Eastern Himalayan Syntaxis region is mainly characterized by crustal thickening, and the flow of the lower crust and upper mantle with viscoplastic characteristics in the deep drives the overall movement of the overlying brittle upper crust block.
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Development Characteristics and Genesis Simulation of Strike-Slip Faults in the Yongjin Area, Middle Junggar Basin

ZHANG Jingqi, YU Fusheng, PANG Fuji, WANG Qianjun, WANG Yuefeng

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Yongjin area is located in the middle of Junggar Basin, northwest China, and several hydrocarbon-bearing structures associated with strike-slip faults have been discovered recently. However, the development characteristics and genetic mechanism of strike-slip faults are not thoroughly studied. Based on detailed interpretation of three dimensional seismic data, three groups of strike-slip fault systems are identified in the Triassic-Jurassic system in the study area, which are nearly east-west, north-west-west and north-east-east trends. The distribution characteristics of the strike-slip fault system are longitudinal stratified and planar "grid" pattern structure. Based on the similarity principle, four groups of structural physical sandbox simulation and comparison experiments were designed to reproduce the tectonic evolution process in the study area. The simulation results indicated that the formation of such kind of strike-slip faults is related to the location of pre-existing faults of the basement. This kind of distributed strike-slip fault system in Yongjin area was controlled by both pre-existing structures and stratum properties, thus a genetic model of the study area has been established. The research results have guiding significance for the genesis of strike- slip fault systems in areas with similar geological settings.
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Moho terraces and its tectonic significance of central Bangong-Nujiang suture zone uncovered by deep-reflection seismic imaging

chengjian, Liu Zhiwei

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Knowledge of the Moho in the Bangong-Nujiang Suture (BNS) is geodynamically of importance to understand the subduction of Meso-Tethys oceanic crust and the genesis of southern Qiangtang depression. Based on deep-reflection seismic data (88o30′E) across the BNS, depth-domain seismic profile and velocity field with high-resolution Moho geometry are obtained by deep-reflection seismic imaging using such techniques as mid/long wavelength static correction, noise elimination, optimal stacking, and PSDM. The depth-domain imaging shows that the Moho of the BNS located at a depth of 65~80 km tends to discontinuously uplift northwards, indicating a few lithospheric mantle terraces (up to 15 km) developed between the Lhasa and Qiangtang terranes. The geometry of the Moho in the BNS demonstrates that the terraces have been driven by southern lithospheric mantle subduction at 19.5o northward and northern crustal uplifting of southern Qiangtang Basin due to possible deep partial melting. The Moho structure suggests that southern Qiangtang Basin gets evolved from marginal marine into foreland basin during the Late Jurassic to the Early Cretaceous along with the Meso-Tethys closure.
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Zircon U-Pb geochronology and geochemistry of Tatuo mafic dykes in East Kunlun orogen, and its geological significance

Zhang Min, Li Ruibao, Pei Xianzhi, Li Zuochen, Pei Lei, Chen Guochao, Chen Youxin, Liu Chengjun, Wu Shukuang

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Early Ordovician mafic dykes exposed in the North Kunlun are of great significance to the subduction processes and dynamic background of the paleo-active continental margin. In this paper, we presented detailed petrology, zircon U-Pb chronology, whole-rock geochemistry and Sr-Nd isotopes of the mafic dykes. Zircon U-Pb dating results show that the zircon U-Pb ages of these dykes range from 486 to 483 Ma, suggesting Early Ordovician. Whole-rock geochemical results show that the mafic dykes have low SiO2 (50.06%-51.68%), medium MgO (5.08%-6.77%) and TiO2 (0.99%-1.20%) content, and belong to the tholeiitic basalt series. For the trace and rare earth elements, the rocks are enriched in large-ion lithophile elements (e.g., Rb, Sr, Ba, Th, K) and depleted high-field-strength elements (e.g., Nb, Ta, Ti); The chondrite-normalized REE diagrams are featured by wild enrichment of LREE and depletion of HREE, with weak Eu anomaly. In addition, the dykes show the high (87Sr/86Sr)i (0.7126-0.7133) and relatively low εNd(t) isotopic composition (-9.80~-4.31) of the enriched lithospheric mantle. The petrogenesis research indicates that the basic magma was originated from the enriched lithospheric mantle ever metamorphosed by fluids in the subduction zone, and then experienced fractional crystallization mainly of olivine and clinopyroxene during the diagenetic processes. Based on the regional geological data, we argued that the Kunzhong Ocean subducted northward in early stage of Early Paleozoic and formed a magmatic arc system. It may have experienced the retreat of the subducting oceanic slab at 486Ma, leading to an extensional tectonic setting in the upper plate of the subduction zone and then generation of mafic dykes.
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Age and rock assembly of Baogutu Formation in West Junggar

LI Yongjun, WANG Xulong, Li wei, DUAN Fenghao, zhuzhao, ZHENG Menglin, YANG Gaoxue, ZHANG Yueqian

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The Baogutu Formation is an important early Carboniferous sedimentary record in the southern margin of the West Junggar accretionary orogenic belt. To confirm the complete sedimentary sequence, rock assemblages and their contact relations with overlying and underlying strata is of great significance for the analysis of Late Paleozoic tectonic evolution of Junggar basin. The newly measuredHongshanliang section in the northern Baijiantan reveals two sets of strata with distinct rock assemblages and strong tonal distinction. The upper gray-black "carbonaceous fine clastic rock" and the underlying bright red "chert, silty chert and tuffaceous chert sandwiched with basic to intermediate volcanic rocks namely conformable contact), belonging to the Baogutu Formation and Hongshanliang Formation, respectively. LA-ICP-MS zircon U-Pb ages of 345 Ma and 365.9 Ma were obtained from the bottom of the Baogutu Formation and the top of the Hongshanliang Formation, and their ages are defined as Early Carboniferous and Late Devonian, respectively. This new discovery not only confirms that the Baogutu Formation is the oldest Carboniferous stratigraphic unit in the region, but also proves that the Baogutu Formation is older than the Xibeikulasi Formation. Moreover, this makes a complete stratigraphic sequence of the Lower Carboniferous in this region and reveals the sedimentary construction and rock assemblage at the bottom of the Carboniferous system, which provides new data for a complete understanding of the sedimentary characteristics and tectonic evolution of the basin during the Devonian to Carboniferous period.
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Discovery and geological significance of andesite intercalation in the “Dibuco Formation” in Nixiong area, Central Tibet

liuhaiyong, tangjuxing, wangyu, tangzuoqi, yeqiang, zengqinggao, kongmingming

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Due to the lack of high-precision chronological constraints, the age and stratigraphic attribution of the "Dibucuo Formation" in Nixiong area are controversial. In this paper, the weighted average age of ~120 Ma was obtained through zircon U-Pb dating from the andesite intercalayion in the "Dibucuo Formation". These data, in combination with the existing research data on detrital zircons of the "Dibucuo Formation" in the studied area, led us to conclude that the so-called "Dibucuo Formation" was formed in Early Cretaceous (130~120 Ma), which is consistent with the formation age of the colcanic-sedimentary strata of the Zenong Group in this region. It is thus suggested to tentatively classify the "Dibucuo Formation" into the Zenong Group. According to the whole-rock geochemistry of andesite samples and the in-situ zircon Hf isotopic composition, it is believed that the andesite was derived from of the mixture of crust-derived felsic magma and mantle-derived basaltic magma, and formed in the subduction tectonic environment. By further summarizing and analyzing the spatio-temporal transformation of Meso-Cenozoic magmatism in the Lhasa Terrane, it is revealed that the dynamic mechanism of the formation of this set of andesites is mainly related to the northward subduction of the Neo-Tethys Oceanic slab.
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The occurrence of cobalt and enrichment characteristics in skarn deposits of Gangdese metallogenic belt, Tibet

Wang Shuo, Xu Yuan, Shan PengFei, SiLang wangdui, Cao MingJian

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As an important strategic key metal, cobalt will become increasingly important with the rapid development of new energy, new materials and aerospace technology. Cobalt often appears in skarn deposits as associated resources, and the associated cobalt resources in some skarn deposits can reach a large scale. Cobalt in skarn deposits is an important source of cobalt resources in China. There are many skarn deposits in the Gangdese metallogenic belt, Tibet. However, there has lacked researches about the enrichment characteristics and occurrence states of cobalt. In this paper, the Jiama, Longmala, Chunzhe, Zhibula, Mengyaa, Nuri, Bangpu, Pusangguo and Yaguila skarn deposits in the eastern Gangdese, and the Bangbule and Chagele skarn deposits in the western Gangdese were investigated. The enrichment characteristics and occurrence states of cobalt in representative ores in the deposit were studied by means of hand-held X-ray fluorescence analyzer, optical electron microscopy observation, scanning electron microscopy observation and electron probe microanalysis. The results of hand-held X-ray fluorescence analysis show that the deposits in the eastern Gangdese are enriched with cobalt to varying degrees. The average cobalt contents of Jiama, Zhibula, Pusangguo and Chunzhe deposits are 853×10-6, 410×10-6, 460×10-6 and 898×10-6 respectively, while the cobalt contents of Bangbule and Chagele deposits in the western Gangdese is basically lower than the detection limit (< 3×10-6). The results of optical electron microscopy observation, scanning electron microscopy observation and electron probe microanalysis show that cobalt mainly exists in the form of cobaltite in Jiama deposit, cobaltite and carrollite in Pusangguo deposit, siegenite in Zhibula deposit. Other skarn deposits in eastern Gangdese are mostly distributed in the form of isomorphism in pyrite, bornite, chalcopyrite, sphalerite, tetrahedrite, tellurite, rather than independent minerals. Based on all the above experimental results and analyses, the enrichment degree of cobalt in the skarn deposits in the eastern Gangdese is distinctly better than that in the western Gangdese, indicating that the eastern Gangdese has better cobalt enrichment potential than the western Gangdese, the cobalt enrichment characteristics of skarns deposits in the eastern Gangdese would be controlled by the deep lithosphere structure. These characteristics may be related to the partial melting of juvenile lower crust in the eastern Gangdese, and the mineralization are not excluding the mixing of atmospheric precipitation. The main purpose of this research is to develop an understanding of cobalt enrichment characteristics and metallogenic mechanism, which can provide reference for subsequent exploration works.
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Enrichment mechanism and occurrence of silver in the Erdaohezi Pb-Zn-Ag polymetallic deposit, Inner Mongolia

LIU Yanrong, GUAN Qiangbing, FAN Wujie, LIU Minwu, YAN Xiaoru, HUANG Fan

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The Erdaohezi Pb-Zn-Ag polymetallic deposit, one of the largest and most representative deposits, is located in the central part of the Derbugan metallogenic belt. The hydrothermal mineralization process is subdivided into four mineralization stages: quartz-pyrite stage (I); quartz-sulfides polymetallic stage (II); quartz-sphalerite-galena-silver minerals polymetallic stage (III); and quartz-calcite-pyrite stage (IV). Microscope observation and electron probe microanalysis (EPMA) analysis suggest that the occurrence of silver in this deposit is mainly visible silver (<1μm), followed by invisible silver (>1μm). Visible silver is mainly microencapsulated silver and independent silver minerals, and invisible silver is mainly super-microencapsulated silver and isomorphic silver. Microencapsulated (super-microencapsulated) silver occurs usually as round or irregular inclusions within sulfides or between sulfides and quartzes. Independent silver minerals are mainly distributed as veinlets or aggregates in microfractures or edges of galena (sphalerite) veins. A very small amount of isomorphic silver exists in the crystal lattices of sulfides. The metal ions in the ore-forming hydrothermal fluids, such as Ag, Cu, Fe, Pb^{and Zn,}are transported as chlorine complex ions in the early mineralization stage and as HS_-^{complex ions after fluid boiling}. With decreasing temperature and pressure of the fluids and mixing of meteoric water, the ore-forming fluid has migrated upward and experienced two silver enrichment processes, : Ag₊released from HS_-^complex is coprecipitated with Cu₊^, Sb₃₊^, Pb₂_⁺ and S₂to form microencapsulated (super-microencapsulated) silver in Stage II; then the instability of Ag(HS)₂_-leads to the complete disintegration of silver from its HS- complex and combination with Cu₊^, Sb₃₊and S_2-to^form independent silver minerals (such as argentite and polybasite) in Stage III.
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Granite, Radon Gas and Human Lung Cancer

MA Xuxuan, Liu Fei, Huang He, Gao LiE, Xiong Fahui, He Bizhu, Li Haibing

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Radon gas is the only radioactive inert gas, whose hazards for human have been confirmed by medical and health science. The WHO report revealed that the inhalation of radon and its decay products was carcinogenic for the human lungs among non-smokers. Approximate 3-15% human lung cancers are triggered by the radon gas among different countries all over the world. The synergistic effect of radon gas and smoke will significantly raise the possibility of lung cancer. In addition, excess radon inhalation will damage human nervous system, decrease the hemameba, and trigger the increasing of blood clotting and hyperglycemia. Radon is the decay product of 238U, whose one main source is the granite. In the granite, the main U-bearing minerals are the accessory minerals such as zircon, titanite, allanite, and pyrochlore, etc. Granite is the main constituent of continental crust of the Earth, occupying the 22% on volume. Lots of studies on granite origin have been implemented among geological community and revealed that the granite was mainly formed in the active continental margin arc setting, the continent-continent collisional orogenic setting, and the intra-plate setting. However, the relationship of human lung cancer and the granite hasn't got enough attentions from geologists. In contrast, the medical and health community know much about the radon gas, but they don't understand the original source of radon gas and its closeness with granite. In the present study, we would like to address the linkage between granite and radon, shed light on the damage of radon gas for public.
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Finite element method-based numerical simulation of the enrichment process of Ge within the Lincang coal-hosted Ge deposit, Yunnan, China

HU XUNYU, DUAN PIAOPIAO, YANG YONGGUO, CHEN YUHUA, LUO JINHUI, YANG HUI, WANG KUN, LIU GUANGXIAN, LI YUE

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The enrichment process of ore-forming materials is a key problem facing ore geology research of the coal-hosted critical metal deposits. Numerical simulation links pressure, heat transfer, fluid-flow and chemical reaction processes is conducted to quantitatively describe the enrichment process of Ge within the Lincang coal-hosted Ge deposit, Yunnan, China. Modeling results are consistent with previous research, verifying the metallogeny of coal-hosted Ge deposits and the effectiveness of numerical modeling approach within ore geology research. The morphology of the upper surface of intrusions is a key factor controlling the enrichment process of ore-forming materials, and intrusions with dome upper surface results in 9.1×103 times of the concentration of Ge comparing to the concentration of Ge participating in chemical reaction. With half the size of intrusion, the enrichment rate can still approach 6.9×103. However, intrusions with depressed and flat upper surfaces can only lead to Ge enrichment of 589 times and 9.3 times, respectively. Therefore, intrusions with dome upper surface can profit the generation of high-grade Ge mineralization within the coal basin, which can provide useful information for future deep prospecting and exploration of coal-hosted Ge deposits with magmatic-hydrothermal origins.
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Distribution characteristics and metallogenic model of sand mineral resources in the South China Sea and adjacent areas

zhoujiao, Yangchupeng, Lixuejie, Caipengjie, Niexin, Tianchengjing, Zhonghexian

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The South China Sea and its adjacent areas have diverse topography and abundant provenance materials, which provide a material source and accumulation environment for the formation and distribution of marine solid mineral resources. In order to systematically find out the distribution of placer resources in the entire South China Sea and its adjacent areas, this paper analyzes the distribution characteristics and prospects of useful mineral placer resources and building sand resources , and summarizes the placer mineralization model through the particle size and clastic mineral identification of surface sediment samples from 2606 stations in the South China Sea and adjacent areas The results show that the promising minerals in the South China Sea and the adjacent areas are mainly include zircon, ilmenite, rutile, anatase, monazite and garnet High grade ore occurrences of heavy minerals are mainly concentrated inthe northeastern and southern continental shelf of the South China Sea, and the Philippine Basin .The anomalous areas of heavy minerals are mainly located in the shallow waters of the peripheral continental shelf of the South China Sea, the shallow waters of the outer shelf of Vietnam and the Philippine Sea Basin. Among them, the anomalous range of zircon grades is the largest (491913km2), and the area with industrial grades is also the largest (144941km2); followed by magnetite, ilmenite, monazite; anatase and rutile are equivalent; garnet grades are the smallest; according to The distribution law of placer deposits, tectonic background, metallogenic conditions and characteristics of metallogenic elements delineate, 24 useful heavy mineral placer metallogenic prospectareas and 6 metallogenic belts have been delineated. There are 9 prospective areas of construction sand with a sand content of more than 50% in the sediments (2mm-0.063mm), mainly distributed in the waters north of the line from the southwest of Hainan Island to the southern part of the Taiwan Strait, followed by Reed Beach and Wan'an in the southern part of the South China Sea. The sea area near Zengmu Shoal and Zengmu Shoal is extremely rare, with a total area of 246,397km2. Based on the distribution characteristics of placer resources in the South China Sea, five types of marine sand metallogenic models including near-shore type, tidal sand ridge type, paleochannel buried type, gorge type, and shelf slope break zone type have been initially established to provide guidance for understanding sand mineral resources in the South China Sea. And reference significance, to provide directions and suggestions for further exploration of sand mineral resources.
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Audio magnetotelluric response characteristics of gas hydrate reservoir in the permafrost based on resistivity logging

XIAO Kun, ZOU Changchun), LU Zhenquan), YANG Yaxin, LI Hongxing, DUAN Zhongyi

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Audio magnetotelluric (AMT) is an effective exploration method to study the electrical structure of strata based on the electrical differences of rocks. The gas hydrate in the permafrost has the characteristic of high resistivity, which is different from the surrounding rock electrically. The AMT method can be used for the exploration and evaluation of gas hydrate in the permafrost. Based on the actual geological characteristics of gas hydrate reservoir in the Qilian Mountain permafrost, the geoelectric model of gas hydrate reservoir is established by combining with resistivity logging. The application range of AMT method for gas hydrate reservoir detection and the optimal acquisition parameter setting scheme were simulated by using finite element method and nonlinear conjugate gradient method. When porosity of gas hydrate reservoir is less than 5%, gas hydrate saturation is greater than 70%, occurrence scale is less than 50 m, or bury depth is greater than 500 m, AMT technique cannot identify and delineate the favorable gas hydrate reservoir. Survey line should be more than twice the length of probable occurrence scale, while tripling the length will make the best result. The number of stations should be no less than 6, and 11 stations are optimal. At the high frequency section (10~1000Hz), there should be no less than 3 frequency points, 4 being the best number. The research results could provide important reference for gas hydrate reservoir electrical prospecting in the Qilian Mountain permafrost.
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The nature of mantle source and the process of sulfide segregation of the Xiarihamu No. I intrusion: insights from olivine, chalcophile elemental and sulfur isotopic compositions

LI Zhongzhou, WANG Yalei, WANG Mengxi, JIAO Jiangang, XIA Mingzhe

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The nature of mantle source of the Xiarihamu Ni deposit is still under debate, with three possible source regions from asthenosphere, sub-continental lithospheric mantle or pyroxenite mantle. In this study, we collected orthopyroxenite and disseminated ore samples from the drill hole ZK3109, and carried out the in-situ analysis on olivine composition of the No. I intrusion to identify the nature of mantle source, and analyzed the in-situ S isotopic composition of sulfide and whole-rock chalcophile elements to portray the processes of sulfide saturation and segregation. Most olivine grains of orthopyroxenite and disseminated ores have low Mn/Zn ratio (< 13.5), and most of those from orthopyroxenite have low 100×Mn/Fe ratio (< 1.35), indicating a pyroxenite mantle component in the source origin. Moreover, the low Ca（< 600×10?6）and high Li with an average value of ~ 9.8×10?6 of olivine from orthopyroxenite and disseminated ores, and the positive correlation of Sc and Ni for olivine from orthopyroxenite, suggesting the pyroxenite mantle was formed by the metasomatism of sub-continental lithospheric mantle by materials from the subducted oceanic crust. On the other hand, the negative correlations of Co concentration with Ni concentration and Fo value of olivine from orthopyroxenite and the ambiguous correlation of S and PGE indicate that the sulfide segregation occurred after the formaton of orthopyroxenite. In contrast, the positive correlation of Co and Ni of olivine and the positive correlation of S and PGE of disseminated ores suggest that the olivine composition is mainly controlled by the sulfide segregation. Pentlandite, pyrrhotite and chalcopyrite of orthopyroxenite and disseminated ore have δ34S ranging from 2.28‰ to 6.11‰, distinctly higher than the mantle value (0 ± 2‰), indicating the S saturation of parental magma in the shallow magma chamber was triggered by the selective addition of crustal S. The modeling results suggest that the different chalcophile elemental compositions of disseminated ores and net-textured ores in the west and east segments of the No. I intrusion were ascribed to different R-values (the mass ratio of the silicate melt to sulfide melt) during sulfide segregation of the parental magma, ranging from 30 ~ 3,000 and 3,000 ~ 15,000, respectively. Therefore, the combination of mineral, S isotopic and whole-rock chalcophile elemental compositions can be a comprehensive way to effectively identify the nature of mantle source and describe the processes of sulfide segregation of the Cu-Ni sulfide deposits.
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Genesis and Geological Significance of ilvaite in Jinchanghe Fe-Cu-Pb-Zn polymetallic deposit, Baoshan Block, Western Yunnan

Lu Bode, Liu Xuelong, Zhou Yunman, Zhao Chengfeng, Wang Jiyuan, Li Fanglan, Li Qingrui, Wang Hai, Li Shoukui, Cao Zhenliang, Zhou Jiehu

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Ilvaite is a common mineral in skarn-type Pb-Zn deposits and Fe deposits, and is closely related to lead-zinc ore bodies and magnetite ore bodies. In order to find out the relationship between the ore-forming process of ilvaite and Pb-Zn-Fe-Cu polymetallic mineralization, this paper investigated the production environment, mineral symbiotic assemblage, chemical chemistry of ilvaite in the Jinchanghe Fe-Cu-Pb-Zn polymetallic deposit. The composition and zonality were studied. Calculated according to the EMPA data, its chemical formula is: Ca0.95-1.08(Fe0.87-1.97Mn0.08-0.36Mg0.01-0.06)1.89-2.032+(Fe0.82-1.04Al0.01-0.03)0.88-1.153+(Si1.94-2.08O7)O(OH). Combined with the type of mineral assemblage, occurrence, zoning characteristics, etc., it was inferred that the skarn in the deposit will gradually metasomatize from the inner zone to the outer zone. There are mainly 3 mineral symbiotic combinations in Jinchanghe mining area: I、Ilvaite + magnetite combination, II、Ilvaite + magnetite + pyrite + chalcopyrite combination, III、Ilvaite + galena + sphalerite + chalcopyrite combination, corresponds to three different alteration stages: the later skarn stage (representative assemblage I), which is dominated by the decomposition of garnet, forming a large number of ilvaites; the retro-alteration stage(representative assemblage II), mainly actinolite, chalcopyrite, and pyrite developed; at the quartz-sulfide stage (representative assemblage III), ilvaite was further decomposed to form quartz, calcite, magnetite, etc. In addition, the distribution pattern of rare earth elements of ilvaite is very similar to that of garnet, which has certain inheritance. The research believes that the ilvaite is the product of the degradation and decomposition of the early garnet, and the ore deposit is gradually metasomatized from the inside to the outside, forming a Mn-rich ilvaite in the lead-zinc-copper ore body and manganese ilvaite in the magnetite ore body banding feature. Mn-rich ilvaite is conducive to the formation of lead-zinc ore, and has an influence on the depletion of magnetite. Meanwhile, it can also provide important scientific significance for the mining area to expose the neutral acid rock and deep prospecting.
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Multiple new paths of extracting lithium from brine: technology, resources, environment and cost

Tianming Gao, Na Fan, Tao Dai

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The traditional precipitation method for extracting lithium has a long production cycle, which is not suitable for brine with low lithium concentration. Therefore, the output of extracting lithium from salt lake grows slowly, which is difficult to meet the needs of new energy industry. Therefore, it is an urgent need for the lithium industry to develop new technology for extracting lithium from brine with high magnesium lithium ratio. This paper summarizes the development of new lithium extraction processes such as adsorption, solvent extraction, membrane and electrochemical methods. It is found that aluminum based adsorbents have been used in industrial production, but its adsorption capacity is significantly smaller than that of manganese and titanium based adsorbents, and the dissolution loss and long adsorption equilibrium time of the latter two are the key factors restricting their industrialization. Neutral phosphorus extractant have attracted the most attention, but it is easy to corrode and appear the third phase. Corrosion free amide extraction system has been used to industrially extract lithium from chloride type brine, but its stability needs long-term attention. Moreover, solvent extraction process has a long process flow and high acid and alkali consumption. The membrane method cannot remove magnesium deeply, so it needs to be combined with other methods to extract lithium, which consumes a large amount of water resources. Electrodialysis and "rocking chair" electrochemistry realize continuous lithium extraction, accelerate the adsorption rate, and avoid the use of eluent. The reduction of power consumption with the optimization of lithium extraction system and working conditions, electrochemical lithium extraction technology will usher in a broad industrial prospect. The resource consumption and environmental impact of the above new process for extracting lithium from brine are less than that of the traditional precipitation method, which has significant competitive advantages for salt lakes with high magnesium lithium ratio, but each has its own disadvantages. Therefore, in the future, lithium extraction from salt lake brine should strengthen the integration and coupling of a variety of new technologies, move forward the lithium extraction process, improve the lithium recovery rate of the whole process and the comprehensive utilization of various resources.
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Petrogenesis of ~500Ma intermediate to acid intrusive rocks in the South Altun: Implications to tectonic evolution

XU Nan, WU Cailai, LIU Chang, ZHAO Miaomiao

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The South Altun orogenic belt is an important subduction-collision complex belt in northwest China, located between the Tarim Basin and the Qaidam Basin. Its early Paleozoic tectonic evolution has been one of the research hotspots in recent years. However, the time limit of oceanic crust subduction has been controversial. In this paper, we study the petrology, geochemistry, zircon U-Pb chronology and zircon Lu-Hf isotope geochemistry of the Manya quartz monzonite, and discuss its petrogenesis and the tectonic environment. The samples show high alkali, potassium-rich, low-titanium, iron-poor and Nd-Ta-Ti anomalies similar to shoshonitic rocks. The quartz monzonites were generated from 511Ma to 495Ma, and the values of ?Hf (t) are mainly range from -3.51 to -0.08, with some positive values ranging from 0.04 to 1.69. Based on our research, we infer that the subducting oceanic crust released large amounts of water when arriving at amphibolite facies boundaries, and triggered the mantle wedge peridotite occurred hornblende metasomatism. Due to the dragging of the subducting oceanic crust, the temperature of the mantle wedge raised, causing the melting of the hornblende metasomatized peridotite, which triggered the partial melting of upper crust materials. Finally, crustal melts mixed with little mantle melts and formed the quartz monzonite. The ~500Ma granites are petrological responds to transition from oceanic island arc environment to active continental margin. Thus, subduction of the southern Altun oceanic crust may have begun at >517Ma.
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Detrital zircon U-Pb dating of the Paleogene lower Ganchaigou Formation in the Qaidam basin and discussion of basin-mountain coupling

Zeng Xu, Fu Suotang, Long Guohui, Wang Guiwen, Wang Bo, Wu Zhixiong, Cui Haidong

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The Qaidam Basin is surrounded by Qilian Mountains, Altun Mountains and Kunlun Mountains. The unique lithology and sedimentary pattern of the Paleogene lower Ganchaigou Formation (E32) in the basin indicate the complex basin mountain system and the diverse genesis of the source area. In this paper, the structure and provenance of the Qaidam Basin are systematically analyzed by using detrital zircon U-Pb dating and other analysis methods. The results show that the E32 zircon ages of the sample from well XX-1 in the front of Qilian mountains range from 155.8 Ma to 2691.9 Ma, and the main peak ages are 249.2 Ma and 448 ma; The E32 zircon ages of l6-1 well samples ranged from 220.2 Ma to 2692.8 Ma, with the main peak ages of 414.9 Ma and 498.4 ma. The E32 zircon ages of YT-1 well samples located in the Western subsidence center of the basin ranged from 266.1 Ma to 2795.8 Ma, with the main peak ages of 255 Ma and 423 Ma. The E32 zircon ages of N-105 well samples in front of Altun Mountain ranged from 241.9ma to 2481.5 Ma, and the E32zircon ages of N-109 well samples ranged from 228.3 Ma to 2637.9 Ma. The main peak ages were 246.4 Ma and 443.8 ma. Compared with the ages of the main source areas, the provenance of E32 in different structural zones of the basin is quite different. The provenance of E32 in XX-1 well and l6-1 well near the front of Qilian Mountains mainly comes from the interior of Qilian Mountains; The main source of well N105 and well N-109 located in front of the Altyn Tagh mountains is from the interior of the Altyn Tagh mountains, but well n-109 has the contribution of Qilian Mountains; The source of YT1 well in Chaixi depression is jointly controlled by Qilian Mountains and East Kunlun Mountains. The results of provenance analysis show that Qilian Mountain has been uplifted on a large scale in the Paleogene, and as the northern boundary of Qinghai Tibet Plateau, it continues to provide provenance for Qaidam Basin; Altun mountain and Kunlun Mountain had taken shape in E32 period, but did not rise on a large scale, resulting in a complex provenance system in the piedmont zone.
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Petrogenesis and geodynamic setting of the Xiaosaishiteng Mountain biotite monzonitic granite and quartz diorite in the western part of the northern margin of the Qaidam Basin: constraints from zircon U-Pb geochronology, geochemistry and Hf isotope

WANG Panlong, LI Yongjun, DUAN Fenghao, ZHUANG Yujun, ZHI Qian, GU Pingyang, GAO Jipeng, YANG Gaoxue

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There are a large number of late Hercynian intermediate-acid magmatic rocks in the Xiaosaishiteng Mountain, located in the western part of the northern margin of Qaidam Basin. Their formation age and genetic types are of great significance to reveal the regional tectonic evolution. In this paper, the Permian biotite monzonitic granite and quartz diorite in the Xiaosaishiteng Mountain are studied by petrology, zircon U-Pb chronology, petrogeochemistry and Lu-Hf isotope. The results show that the ages of biotite monzonitic granite and quartz diorite are 272±3Ma and 273±2Ma, respectively, indicating that they were formed in Early-Middle Permian. Geochemical results show that biotite monzonitic granite belongs to I-type granite of weakly peraluminous potassium basalt series, and quartz diorite belongs to I-type granite of quasi-aluminous calc-alkaline series. Both of them are enriched in large ion lithophile elements Rb, Th, K to varying degrees, and depleted in high field strength elements such as Nb, Ta, Ti, showing typical arc magma characteristics. Lu-Hf isotope compositions indicate that biotite monzonitic granite has a positive εHf(t) value(2.04~8.16), and younger two-stage Hf model age(tDM2=0.77~1.16Ga). Combined with previous research results, it is considered that the Early-Middle Permian biotite monzonitic granite and quartz diorite in the Xiaosaishiteng Mountain were the products of subduction of the Zongwulong Ocean. The quartz diorite was formed by the melt contaminated by mantle peridotite caused by the partial melting of the basaltic oceanic crust plate, and the biotite monzonitic granite was formed by partial melting of the mixed crust composed of the juvenile crust and the ancient basement crust under the condition of amphibolite facies, which is caused by the magma underplating generated by oceanic crust melting.
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Genesis discrimination of ferromanganese nodules in Pacific Ocean using Gaussian Mixture Model

YANG Yong, WANG Tao, HE Gaowen, REN Jiangbo, ZHANG Limin, YANG Shengxiong, LIU Yonggang

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The genetic classification of ferromagnanese nodules is an important geological problem in seabed mineral resources. The discrimination of nodules by geochemical characteristics has been concerned widely beginning at the discovery of nodules in the seabed. In recent years, with the application of Big Earth Data mining and the application of machine learning technologies, creative idea and method is caused for the discrimination of nodules by geochemical characteristics. Based on the geochemical data of ferromaganese nodules obtained in Pacfic Ocean over the years, the four types of nodules in deep-sea basin, the diagenetic, mixed, hydrogenetic-I and hydrogenetic-I types, have been identified successfully by Gaussian Mixture Model cluster analysis technology. Furthermore, the spatial prediction results of different genetic types of nodules show that the northwest Pacific ocean is one of the main distribution areas of hydrographic-I cobal-rich nodules. This genetic type are mainly distributed in the inter-mountain basins of Marcus-wake seamounts, the north of Magellan seamounts, the Marshall seamounts and the southwest of Central Pacific seamount group, as well as the nearby Pigafetta basin and the northwest of central Pacific basin.These basins are perspective areas for the future exploration of cobalt-rich ferromaganese nodules in the northwest Pacific ocean.
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Structural exhumation process and geological significance of ductile detachment zone of the Sonid Zuoqi metamorphic core complex in early Mesozoic

lijianbo, Wang Zhiyong, Song Zhijie, Zeng Tao, Lei hengcong

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The Sonid Zuoqiductile metamorphic core complexes, which is located on the south-eastern margin of the CAOB, includes a extensional ductile detachment zone which strike EW and dip to S. The footwall of this detachment zone consists of Permian-Triassic intrusions, ductile shear zone (mylonite zone) and brittle detachment fault zone, and the hangwall composes of Palaeozoic and Proterozoic rocks. The major rock types of the Sonid Zuoqi ductile detachment zone is mylonites which are generally characterized by a down-dip stretching lineation which plunges to 15°-39° toward 185°-228°and well-developed mylonitic foliation (S-C foliation) which dips toward145°-194°at 34°-55°. At the microscopic scale, the quartz is strongly oriented to wire-drawing and has sub-particle recrystallization. The feldspar forms asymmetric rotational cataclastic system and core-mantle structure. Shear-sense indicators such as asymmetric porphyroclasts, S-C fabric and mica-fish, consistently indicate top-to-the-SW shear. Zircon U–Pb dating yields ages of 244.1±2.1Ma, 243.5±2.3 and 230±2.7Ma for Strong deformation mylonite and the overlapping granite with the detachment zone, respectively. The strong deformation mylonite and Halatu plutons within the footwall of detachment zone are taken as the dating objects and yields Zircon U–Pb ages of 244.4±1.8Ma, 244.0±2.4 and 229.4±2.1; (U-Pb)/He age of 212.5±13.1 and 214.1±13.2 Ma for two strong deformation mylonite and the granite with the detachment zone, respectively. Combined with the regional tectonic background and previous research data, it is considered that the initial deformation time of the Sonid Zuoqi detachment zone is after 244 Ma, and the deformation peak time is 224 Ma and continues to 213 Ma. The cooling rates of the ductile detachment zone of the Sonid Zuoqi metamorphic core complex during 244 Ma to 224 Ma and 224 to 213 Ma are 18.5℃/Ma and 16.3℃/Ma, respectively, and the uplift rates are 0.54Km/Ma and 0.48Km/Ma, respectively. The early simple shear-dominated general shear and the late pure shear-dominated general shear jointly restrict the structural denudation process of the Sonid Zuoqi metamorphic core complex. The results of this paper show that there was a rapid crustal uplift event in the early Mesozoic between the northern margin of North China and the Central Asian orogenic belt, which may be the result of the combined action of the collapse after the final closure of the Central Asian orogenic belt and the remote effect of the Mongolia-Okhotsk tectonic belt.
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Contributions of metamorphic recrystallization in the metallogeny of sparry magnesite deposit

Hu Guyue, Wang Denghong, Zheng Jun, Yu Xuhui, Wu Wenbo, Song Lijun, Zhu Yongxin

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Abstract:

The sedimentary-metamorphic sparry magnesite deposits are hosted in the Mg-rich marine carbonate Formations and suffered metamorphic recrystallization of late-stages. Geochemical and stable isotope (C and O) study has been carried out on three typical magnesite deposits suffered by high-, medium- and low- metamorphic grades. Geological observation and geochemical data shows: (1) The magnesite ores that hosted in Paleozoic marine sedimentary rocks endured low grade metamorphic recrystallization, shows relatively low contents of Magnisium (44.98%~47.35%), and inherited the marine carbon isotopic characteristics (δ13CV-PDB: -0.4‰~+0.3‰). (2) Most of the large-class (>50 Mt) magnesite deposits in China are located at the Paleoproterozoic Jiao-Liao-Ji belt, east margin of North China Craton. These magnesite ore endured medium grade metamorphic recrystallization, shows relatively high contents of Magnisium (wt.(MgO)>46%), and inherited the marine carbon isotopic characteristics (δ13CV-PDB: -1.9‰~+1.7‰). (3) The magnesite ores that endured high grade metamorphic recrystallization with large crystals (particle size of more than 1cm), altered by silica-metamorphic fluids. These serpentinized magnesite ores show relatively low contents of Magnisium (wt.(MgO) : 44.42%~45.55%), high contents of FeOT，Mn, Ti, and low carbon isotopic compositions (δ13CV-PDB: -4.1‰~-3.5‰). Therefore, the magnesium enrichment process may be happened during the marine sedimentary and diagenetic epoch, with the sparry magnesite ores formed during the metamorphic recrystallization of late-stages. The Mg- and Ca-carbonate may occur fractional crystallization during the metamorphism, formed the dolomite interlayers in the magnesite orebodies, the high (high amphibolite to granulite facies) or low (greenschist facies) metamorphic recrystallization were not beneficial to the development of sedimentary-metamorphic sparry magnesite deposit.
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Detrital zircon U-Pb age signatures of coarse-fine fractions in the Horqin Sand Land: Implications for quantitative provenance and regional tectonic-magmatic evolutionary events

WangYehui, XieYuanyun, ChiYunping, KangChunguo, WuPeng, SunLei, LiuRuonan

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Tracing the provenance and aeolian-fluvial interaction mechanisms of large sandy lands in arid and semi-arid regions is essential for understanding the evolution of terrestrial landscape patterns, surface processes and geomorphological dynamics, and the linkages between the atmosphere and lithosphere. However, the provenance of the Horqin sandy land is still highly controversial and there is a lack of statistically significant zircon U-Pb age database. Therefore, in this study, multi-point sampling of surface aeolian sand from the Horqin sandy land was collected, and 1500 detrital zircons were selected for U-Pb dating analysis according to different grain-sizes (i.e., <63 μm and >63 μm). Then, the inverse Monte Carlo model were quantitatively constrained provenance of the Horqin sandy land. The results shows that the detrital zircon U-Pb age spectra of the Horqin sandy land are very similar from a visual qualitative point of view. However, the quantitative reconstruction results show that the source of the aeolian sands is overall dominated by the contribution of the Central Asian orogenic belt (50.5%-61.3%), however, the southeast of the Horqin sandy land reflects the absolute dominance of the North China Craton (~75.8%). There is spatial heterogeneity in the sources of the Horqin sandy land, with zircon age spectra in the western and northern parts of the sandy land being extremely similar and significantly different from the zircon age signature in the south. The signature of detrital zircon U-Pb ages in the Horqin sandy land is largely unaffected by grain-size sorting, except in the southeastern part of the sandy land. Thus, we suggest that the synergistic effect of wind and fluvial and their resulting sedimentary sorting and recirculation is the main reasons of the U-Pb age signature of detrital zircons in the Horqin sandy land. Combined with the regional tectonic evolution history, the peak ages at ~2.5 Ga and ~1.85 Ga in the Horqin sandy land are the products of the two tectonic events during the growth, collapse and collision of the North China Craton during early Precambrian, respectively. In addition, the ~1.7 Ga zircon age may be a combined response to the convergence and rifting of the Columbia supercontinent. The zircon peak ages (e.g., 400-500 Ma, 250-300 Ma and 110-130 Ma) since the Paleozoic record multi-phase regional tectono-magmatic events in the regional tectonic context of subduction and closure of the Paleo-Asian Ocean, subduction and collision of the Mongolian-Okhotsk Sea, and subduction and retreat of the Paleo-Pacific Ocean.
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Surface process response to the expansion of the northern South China Sea: Age evidence of apatite fission tracks from Wuzhi Mountains , Hainan Island

shijunhua, Hanshuai, Dujianjun, Hanjianen, Sundongxia, Hudaogong

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Hainan Island is an important part of the South China Sea block, and its tectonic evolution can largely reflect the tectonic activity characteristics of the entire South China Sea. During the Cenozoic period, under the neotectonic movement of Hainan Island, the differential rise and fall of fault blocks was relatively obvious, forming a tectonic pattern roughly bounded by the Wangwu-Wenjiao fault, with the subsidence area to the north and the fault-uplift area to the south. Research on the uplift process of the faulted uplift area can reveal the history of neotectonic activity in Hainan Island, but so far, the reason and time limit for the uplift of the southern Qiongzhong Mountains are still controversial. In order to clarify the exfoliation and uplift events in the central part of Hainan Island, this paper selects the Wuzhi Mountain with the highest elevation and the largest elevation difference in the southern Qiongzhong area as the study area, and collects 8 sets of rock elevation samples in this area, with an elevation range of 1153.52-203.55m. A large number of apatite fission track tests and thermal history simulation analysis were carried out on the collected samples. The results show that the Cenozoic in the Wuzhi Mountain area of Hainan Island mainly experienced two periods of rapid uplift and exfoliation. The first period is from Oligocene to Miocene (32~17Ma): the uplift rate is relatively fast. During this period, the Pacific plate subducted and retreated to the Eurasian plate, and the South China Sea is experiencing the second expansion, making Hainan Island in the context of extension The activity was intense, causing the Qiongzhongshan area to uplift rapidly until it turned into a slow uplift during the Middle Miocene. The second stage is the stage of rapid denudation and uplift at the end of the Miocene (5Ma): the expansion of the South China Sea has ended. With the subduction of the Asian plate by the Philippine plate, the entire northern continental margin of the South China Sea is in the stage of accelerated thermal subsidence, and the global climate change has accelerated, resulting in Extensive uplift and accelerated denudation in Hainan Island.
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Distribution and source of bromine in the brines from the salt-bearing basins in China

song hualing, Fan qishun, Li qingkuan, Liu wanping, Han guang, Han chunmei

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The salt-bearing basins in China occurred in salt lake brine and deep brine resources and enriched in bromine (Br) elements, which have potential development and utilization value. As an important resource element in brines, systematic comparative studies on Br distribution and sources have been rarely reported. Qarhan Salt Lake (QSL) in Qaidam Basin is the largest potash production base in China and a large comprehensive brine deposit with rich resources. In this paper, the intercrystalline brines of four sections of QSL was taken as the research object to analyze the distribution and source of Br in the whole lake area, and compared the change and provenance of Br in brines from different salt-bearing basins in China, and summarized the value of development and utilization. The results show that: (1) the Br concentrations in QSL are high in east and low in west, and the difference is obvious in different sections; (2) the lower Br in Beiletan and Dabuxun sections are recharged by rivers and enriched by evaporation, while the higher Br in Qarhan and Huobuxn sections are recharged by upwelling spring with high Ca in the northern fault zone; (3) the high Br values of most deep brines in salt-bearing basins of China (Qaidam Basin, Kuqa Basin, Jianghan Basin, Jitan Basin) are mainly obtained by leaching of water-rock reaction and desorption of Br in sediments and organic matter; (4) although the Br concentrations in brines of salt lake is far less than that in deep brine, it has the advantages of easy development and high comprehensive utilization rate. In particular, the predictability of Br in concentrated brine and old brine is higher than that of industrial grade, so it is a resource worthy of attention at present and in the future.
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Isostatic rising in the Linglong bivergent metamorphic core complex: Indication from kinematic vorticity

WU Xiaodong, ZHU Guang

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Early Cretaceous extensional structures around the Linglong batholith in the northwestern Jiaodong Peninsula belongs to a bivergent metamorphic core complex (MCC). The MCC is bounded by the Zhaoping and Jiaojia detachment shear zones in the east and west respectively. It is not clear whether or not isostatic rising also contributes to exhumation of the bivergent MCC. In this study, kinematic vorticity measurements were conducted to mylonite samples from different localities of the two boundary shear zones by means of the rigid porphyroclast aspect ratio (RPAR) methods, (including the Rigid Grain Net and Wallis plot methods) and the quartz c-axis fabrics-finite strain ratio (RXZ/β) method. The Zhaoping shear zone gives vorticity values of 0.57~0.73 from the RPAR measurements, and 0.80~0.93 from the RXZ/β measurements. The Jiaojia shear zone yields vorticity values of 0.58~0.74 from the RPAR measurements, and 0.79~0.93 from the RXZ/β measurements. For the same mylonite samples, the two methods give different vorticity values. The two shear zones give higher thinning rates from the RPAR measurements than those from the RXZ/β measurements. Theoretical analysis and other examples suggest that vorticity values obtained from the RPAR measurements represent earlier deformation whereas those obtained from the RXZ/β measurements indicate later deformation. It is suggested therefore that the boundary shear zones in the Linglong bivergent MCC evolved with reduction in pure shear component due to isostatic rising and resultant steepening of the shear zones caused. The isostatic rising took place at a later stage of the Linglong MCC evolution, and resulted from emplacement of the syn-tectonic, Guojialing-stage granodiorites of the Early Cretaceous age. Our results show that both bivergent and asymmetrical MCCs share similar evolution with isostatic rising at their later stages that has important contribution to exhumation of middle-lower crust.
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Inversion of feldspar content in granite based on hyperspectral indices developed from multi-angular bidirectional reflectance

Wu Mengjuan, Jin Jia, Wang Jinlin, Wang Quan

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The quantitative estimation of feldspar content in granites is helpful for naming and classification of granites, which provides basic data for subsequent study of related geological processes. In the range of visible near-infrared to short-wave infrared (0.35~2.5μm), the traditional method of inversion of rock types and mineral contents based on spectral absorption characteristic parameters is not suitable for minerals with no diagnostic absorption characteristics such as feldspar. At the same time, due to the complexity of the calculation of the radiative transfer model based on physics, the application of this method in the inversion of rock mineral properties is limited to a large extent. In this paper, a spectral index model for estimating the proportion of plagioclase to feldspar in granite was established based on multi-angle hyperspectral data by combining different spectral preprocessing methods and spectral index types. The results show that the double differences type index model based on the measured data set with the continuum removal at 2035nm band (CRDDn2035) has good performance in different measured data sets, and the estimation accuracy is 0.81. Through the study of this paper, a spectral index model for estimating the proportion of plagioclase in granite is established, which provides a new technical method and idea for quantitative inversion of rock and ore information with weak absorption characteristics.
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Volume 97,2023 Issue 8

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Volume 97,2023 Issue 8

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