Welcome to visit Acta Geologica Sinica Editorial Office

Current Issue
Online First

Online-CNKI

Archive

Select All

Display Method:: |

Select All

Display Method:: |

Progress of prospecting prediction research for karstic bauxite in China

LOU Bode, ZHANG Qizuan, JIANG Sha, LIU Huan, LI Wanyue, DONG Jianhui, ZHOU Shangguo, CHEN Xu

Submitted date:2023-08-26,Pre-publication date:March 04, 2024

DOI: 10.19762/j.cnki.dizhixuebao.2023374

Abstract: (41) HTML (0) PDF (9.67 MKB)(339)

Abstract:

Karst bauxite is the most important source of bauxite in China, accounting for more than 90% of the total resources, mainly distributed in the North China Craton and the southwest margin of the South China Block. In recent years, as a kind of strategic scarce mineral resource, the prospecting prediction of bauxite has become extremely urgent. This paper systematically summarizes the results of karst bauxite prospecting prediction and explores the optimal combination of prospecting prediction methods, so as to summarize the prospecting experience. By combing the examples and methods of geology, geophysics, geochemistry, remote sensing and artificial intelligence of geological big data to review the research results of karst bauxite prospecting and prediction in China, it is considered that geology and geophysics are still the most major methods for Chinese karstic bauxite prospecting prediction at present. In addition, the limitation of geochemical and remote sensing methods in searching for paleo-karst bauxite and their causes are analyzed, and the far-reaching significance of intelligent prospecting with geological big data is pointed out in the future.
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

Submitted date:2022-12-14,Pre-publication date:February 02, 2024

DOI: 10.19762/j.cnki.dizhixuebao.2023373

Abstract: (46) HTML (0) PDF (27.67 MKB)(184)

Abstract:

The Gangdese metallogenic belt (GMB) in Tibet, located within the East Tethys metallogenic domain, is one of the most famous Pb, Zn, and other nonferrous metal areas in China. A notable discovery in recent years is the Pusangguo deposit, which is rich in cobalt and contains Cu–Pb–Zn ores. The ore bodies mainly occur within the contact zone between the magma and the Early Cretaceous Takena Formation strata, displaying a complex mineralization pattern. Within the Pushangguo deposit, sphalerite is one of the main sulfides in the quartz-sulfides mineralization stage. Notably, there are two distinct types of sphalerite: dark-brown type I sphalerite (SpI) and light-brown type II sphalerite (SpII). This paper employs electron microprobe analysis (EMPA) and laser ablation inductively coupled plasma mass spectrometer (LA-ICP-MS) to analyze the trace elements present in sphalerites. The results show that sphalerite is generally rich in Co, with SpI exhibiting a higher Co content than SpII. Co mainly replaces Zn (Co2+→Zn2+) through isomorphism. Both SpI and SpII showcase enrichment of Fe, Mn, and Cd, as well as depletion of Ga, Ge, and In. The occurrence of Fe, Mn, Cd, and other elements is mainly in the form of isomorphism, while Cu, Ag, Pb, and As appear as mineral inclusions within sphalerite. Based on the observed correlation between different trace elements, it is proposed that there exist potential simple complex element substitution mechanisms. These mechanisms include Fe2++Mn2+→2Zn2+, (In3+, Sn3+)+(Cu+, Ag+)→2Zn2+, As3++Ag+→2Zn2+, and Pb2++2As3++□→4Zn2+ (where □ represents a lattice vacancy). Furthermore, the ratios of Fe, Mn, Ge, In/Ga, In/Ge, and Zn/Cd in sphalerite, along with the calculations based on the sphalerite GGIMPis geothermometer, indicate that sphalerite was formed in an environment of medium-high temperature (237~345℃), low oxygen fugacity, and low sulfur fugacity (logf(S2)=-13.4~-8.3).

Select All

Display Method: |

Geochemistry, monazite geochronology, and metallogenic relation of Kajiya two-mica granite and rare-metal pegmatite in Zhawulong deposit area, western Sichuan (China)

gaojianguo, zhoumingzhao, zhengbihai, ligaungwei, jinwenkai, zhuwenbin, xuzhiqin

Abstract: (4) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

Rare lithium–beryllium metals are critical resources both nationally and globally. The United States, Australia and Japan have long listed Li-Be minerals among the raw materials prohibited for export, which only strengthens their strategic potential. In China, Li-Be mineral resources are not only abundant, they possess a superior metallogenic setting; however, their distribution is uneven and covered by substantial Quaternary deposits. In recent years, field research has gradually revealed an extent of granitic pegmatite lithium deposits in the Tianshuihai-Songpan-Ganze orogenic belt, capturing the attention of the domestic and international scholarly community. The prominent Zhawulong granitic pegmatite lithium deposit in Shiqu County, western Sichuan Province, lies in the middle part of this orogenic belt. Identifying the main controlling factors of lithium resource accumulation and the rules of rare metal enrichment for this deposit will provide a foundation and guidance for the next stage of strategic prospecting along the Tianshuihai-Songpan-Ganze orogenic belt. This paper presents a study on systematically sampled spodumene-albite pegmatite dike, muscovite-albite pegmatite, tourmaline-albite pegmatite dike, Kajiya two-mica granite pluton, fibrous tourmaline aplite, and staurolite-biotite schist from the pluton’s edge. LA-ICP-MS monazite U-Th-Pb isotope dating precisely identifies Zhawulong Kajiya two-mica granite’s formation date in the Late Triassic at 211–213 Ma, fibrous tourmaline aplite at c. 210 Ma, muscovite-albite pegmatite at c. 200–210 Ma, and Li-rich pegmatite at c. 205 Ma. Combined with previous geochronological data, analysis suggests a narrative of progressive formation from two-mica granite and fibrous tourmaline aplite to muscovite-albite pegmatite and spodumene-albite pegmatite. After 210 Ma, magma gradually entered the magma-hydrothermal stage, with an approximate 10 Ma period of continuous and multistage magmatic-hydrothermal activities. Combined with the trace characteristics of REE, K/Rb, Nb/Ta and Zr/Hf, which exhibit decreasing values from granite to pegmatites, and negative Nd and Eu anomalies in the monazite of highly evolved pegmatite, this study reveals the important role of granitic magma crystallization and differentiation in the process of rare metal enrichment for the Zhawulong deposit.
1
Organic-matter-rich shales of the early Carboniferous and their importantly potential implications of the shale-gas exploration in the region from the southern Guizhou to central Guangxi province of South China

MEI Mingxiang, Chen Jiyu, Zhang Yingjie

Abstract: (1) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

In an inter-platform basin facies within the Dianqiangui Basin that was located in the southwestern part of the South-China plate, a set of organic-matter-rich shales with a total thickness of near 300 m and a total a relatively higher total organic carbon (TOC) value of more than 2%, i.e. the Luzhai Formation (Fm.), was centrally developed and formed in the relatively third-order sea-level rising period from the Tournaisian and the Visean Ages of the early Carboniferous, which makes up an importantly potential target rock for shale-gas exploration. A special forming time, a diachonism that is marked by a complex change to the Yingtang Fm. on the attached-platform setting through both the decrease of thickness and the facies changing, and an end with the development of a set of coal measure strata caused by delta sedimentation all characterize a particularly sedimentary succession of the early Carboniferous (the Missippissian) in the study area that was dominated by Luzhai Fm. with a great difference from the sedimentary succession on supercontinent of Pangaea. Actually, this great difference further reflected as the following fact, i.e. only the upper part of the Carboniferous System (the Pennsylvanian Subsystem) harbors enormous volumes of coal and the lower part (the Missippissian Subsystem) contains an unusually large proportion of limestone on Pangaea. The accumulation of organic matter within organic-matter-rich shales that made up the anoxic basin facies of the Lower Carboniferous in study area is generally tally with a fundamental and comprehensive model, i.e. accumulation of organicmatter is controlled by complicated interactions among the three factors: the enhanced productivity and the organic matter preservation, and the decreasing sedimentation rate that led to the weakening of dilution to organic mater, and all of which were directly affected by relative sea-level fluctuations. However, the accumulation of organic matter can not be excluded to the biological carbon pump especially for one of phytodetritus, although there are many detail problems need to further research.
1
The strata constraint on large scale sandstone-type uranium mineralization in Meso-Cenozoic basins, Northern China

chengyinhang, Jinruoshi, Michel Cuney, V. A. Petrov, Miaopeisen

Abstract: (2) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

The "red-black" coupling sedimentary architecture is one of the most important ore-control features of sandstone-type uranium deposits in the Middle and Cenozoic basins of the Northern China (referred to as the Northern Basins), which has been widely validated and applied in exploratory strategies. Simultaneously, more than 300 prospecting targets and orefields have been detected, and the the metallogenic theories have made considerable progress. The findings from more than 600,000 meters of boreholes in the Northern Basins are methodically summarized in this publication. Additionally, a comparative analysis of the sedimentology and geochemistry of typical deposits serves as the basis for a thorough assessment of the depositional conditions and material compositions of the Cenozoic, Cretaceous, and Jurassic reservoirs in the Northern Basins. This gave additional insight into the actual reservoir conditions that control metallogenic fluid flow and uranium mineral precipitation. The findings demonstrate the Northern Basin has developed seven sets of red beds since the Jurassic: (1) I. the Middle Jurassic-Early Late Jurassic (Bathonian-Oxfordian) red beds, II. Early Cretaceous (Valanginian) red beds, III. Late Early Cretaceous (Aptian) red beds, IV. Early Late Cretaceous (Cenomanian) red beds, V. Late Late Cretaceous-Early Palaeocene (Campanian-Thanetian) red beds, VI. Early Cenozoic (Aquitanian-Burdigalian) red beds, VII. Late Cenozoic, (Zanclean-Piacenzian) red beds. The red beds, along with the underlying black organic-rich strata, built upon the reservoir foundations for large-scale uranium mineralization in Northern Basins. (2) Geochemical indicators show that the Fe2+/Fe3+ ratio in the red strata range from 0.29 to 1.47, with an average value of 0.79 and a median of 0.75 (n=78), the Fe2+/Fe3+ ratio in the black strata range from 0.57 to 53.96, with an average value of 4.29 and a median of 2.82 (n=223), and the Fe2+/Fe3+ ratio in the orebodies range from 1.00 to 26.45, with a average value of 7.01 and a median of 4.62 (n=52). The growth of pyrite, carbon debris, and oil spots, which indicate the reduced environments, are characteristics of the orebodies and black strata with Fe2+/Fe3+ ratios that are typically more than 1. The red strata's Fe2+/Fe3+ ratio is typically less than 1, and they are distinguished by the formation of calcareous nodules that presenting strong oxidising environment. (3) As to the carbon content, the red strata range from 0 to 0.16, with an average of 0.046 and a median of 0.041 (n=107), the orebodies range from 0.01 to 2.65, with an average of 0.32 and a median of 0.14 (n=137), and the black strata range from 0.01 to 2.66, with an average of 0.36 and a median of 0.18 (n=339). Additionally, the enrichment and precipitation of uranium are intimately tied to the orebodies' carbon content that slightly less than the black strata. (4) Red beds, black strata, and sandstone-type uranium ore reside together closely in space. The uranium ore bodies usually occurred at the transitional zones between the red beds and black strata. The oxygenated uranium-bearing fluids migrate through the red beds, progressively eating away at the black strata' reducing medium and causing mineralization to occur. This process continues deep into the basin's interior. The ore bodies are mostly tabular-like and occur in gray, grayish green sandstone, fine sandstone, and even in mudstone. Large-scale uranium concentration and mineralization are not appropriate for regions with excessive oxidation or reduction. Large-scale uranium mineralization in the Northern Basins requires paired deposition and cyclic filling of the red and black strata. In the Northern Basins, the superposition of "red and black" strata results in multi-layer mineralization. This has significant practical implications for the deployment of exploration efforts as well as for a thorough understanding of the metallogenic environment, regularity of ore formation, and metallogenic mechanism.
1
Pegmatite-type mineralization of rare metals in the Altai orogenic belt, northern Xinjiang

Chen Yanjing, Han Jinsheng

Abstract: (5) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

Granitic pegmatites are closely related to rare metal mineralization (e.g., Li, Be, Nb and Ta). Although abundant studies and discussions have been carried out on the metallogenic model of pegmatites and the genetic relationship between pegmatites and granites, controversies still exist. The Altai orogenic belt in northern Xinjiang is well-known due to a large number of well-investigated pegmatite-type rare-metal deposits. This paper systematically synthesizes the geological background and metallogenic characteristics of the Altai pegmatites, clarifies three genetic relationships between pegmatites and granites in the Altai orogenic belt: 1) The pegmatites were formed from independent pegmatitic melts via anataxis, showing no genetic connection with granites; 2) The pegmatites are "brothers" of the coeval and proximal granite in genesis; 3) The pegmatites present as sons of parental granite, and both them belong to a granite-pegmatite magmatic system. Meanwhile, we propose a petrogenetic-metallogenic model for the pegmatite in the region, and speculate that pegmatites of different genetic styles may coexist at province-, orefield- and deposit-scales. The formation of the Altai pegmatite-type rare metal province largely benefited from the Paleozoic strata. In addition, the Altai orogenic belt is located in a mantle slope zone and is susceptible to far-field impact from external tectonic events. In the Triassic, the formation of rare metal-bearing pegmatites was triggered by the far-field impact of the northward collaging of a series of landmasses divorced from the Gondwana Land (Tethys tectonic domain) to southern margin of Eurasia. In the Jurassic, the tectonic framework and the petrogenesis as well as the mineralization in the Chinese Altai were jointly affected by the far-field impact of the Neo-Tethys and the Mongolia-Okhotsk Ocean tectonic events.
1
VELSD1.0: a volcanic eruption landform dataset based on remote sensing image for Changbaishan area with deep learning

LI CHENGFAN, HAN JINGXIN, WU CHENGZHI, LIU LAN, YAN LILI, LIU XUEFENG, ZHAO JUNJUAN

Abstract: (3) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

As one of the most well preserved polygenetic composite active volcanoes, the surface cover types in the Changbaishan Mountain volcanic eruption landform scene are widely developed and the interpretation labels in remote sensing image are clear. The remote sensing dataset is currently an important data foundation for large range volcanic eruption landform classification based on deep learning methods from remote sensing image. In this paper, a volcanic eruption landform scene dataset (VELSD 1.0) from Sentinel-2 remote sensing image for deep learning classification in Changbaishan Mountain, China is presented in combination with geological data and field investigations. In the dataset, it includes ten kinds of surfacec over types (i.e., high vegetation coverage, middle vegetation coverage, low vegetation coverage, exposed soil, basaltic rocks, trachytic rocks, mixed rocks of trachyte and pumice, water, shadow, and artificial landscape) as well as three constituent elements (i.e., remote sensing image, labeled data, interpreted label and explanatory file). Covering an area of 2500 km2, the dataset has approximately 40000 sample images of volcanic eruption landform which the image size of each sample is 25 pixels×25 pixels and the spatial resolution is 10 m. The classical convolutional neural networks (e.g., GoogLeNet, ResNet) and Transformer-based (e.g., Vision Transformer, Swin Transformer) deep learning models are used to validate and analyze the proposed VELSD 1.0 dataset. The experiments show that the proposed dataset has good applicability and transferability for deep learning models, and the overall classification accuracy (OA), Kappa coefficient (KC), and mean average precision (mAP) reached 82.93%, 75.64%, and 84.22%, respectively. It can effectively support the deep learning classification of other volcanic eruption landform scene from remote sensing image, and improve the informatization and intellectualization of remote sensing surveys for volcanic landform.
1
Enrichment characteristics and occurrence state of lithium in claystones of Upper Permian Longtan Formation in Xingwen area, south Sichuan

HAOXUEFENG, TANGYI, PANMENG, HEYANG, ZHOUSONGDE, HEYANGPIAO, FUXIAOFANG, LIANGBIN

Abstract: (3) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

Southern Sichuan is located in the middle-outer zone of the Permian Emeishan Large Igneous Province, extensively distributed with claystones of the Lower Permian Longtan Formation related to igneous rock eathering-deposition , with geological background and metallogenic conditions for forming lithium and other critical metal resources.In this paper, a systematic geological survey of the lower part of the Upper Permian Longtan Formation in Xingwen area of southern Sichuan has been carried out, and the chemical analysis of samples from the study area and drill cores has been carried out to determine the distribution and enrichment of lithium in the claystones. On this basis, the mineral composition of the lithium-rich claystones was analyzed by powder crystal X-ray diffraction (XRD), and the distribution characteristics of the elements on the micrometer scale were analyzed by focused-ion-beam and time-of-flight secondary ion mass spectrometer (FIB-TOF-SIMS). The results show that the claystones in the lower part of Longtan Formation are rich in Li, Ga, Nb and other elements, which is a rich layer of several critical metals, and has good ore-forming potential and prospecting prospect.These claystones originate from weathering processes of volcanic rocks within the Emeishan Large Igneous Province. The lithium-rich rocks are mainly pyrite-bearing kaolinite claystones, and their sedimentary environment is the saline environment of lagoons in the transition area of sea and land. The Li content is closely related to the chemical weathering intensity (CIA index), which shows the characteristics of weathering-sedimentary deposits. In addition to a small amount of in lepidolite,lithium is mainly adsorbed in the montmorillonite phase of claystones, some of it enters the montmorillonite mineral structure, and some of it occurs in illite. Besides weathering release from volcanic rocks, a portion of lithium potentially originates directly from coastal shallow groundwater, contributing to the formation of high-grade lithium-bearing mica within lithium-rich claystones.
1
Tracing the migration and extreme enrichment of critical metals using metal-stable isotopes

Xia Hu, Gengxin Deng, Xuqi Chen, Jiaru Sheng, Fang Huang

Abstract: (3) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

Critical metal minerals are significant to the national economy and security, but whether their enrichment is controlled by the fractional crystallization process or by the magmatic-hydrothermal interaction remains controversial. Traditional geochemical methods can only indirectly restrict the source of ore-forming materials, and it isn"t easy to distinguish the effects of fractional crystallization and magmatic-hydrothermal processes on mineralization. The isotope systems of fluid-active metals such as Rb, Ba, Sr, and U have different responses to these two mechanisms. We have studied the Rb and Ba isotopes of granites collected from the Himalayas and South China. Our research shows that the Ba isotope in the residual melt becomes heavier and the Rb isotope remains unchanged during mineral crystallization, while the Ba isotope in the granite becomes lighter and the Rb isotope becomes heavier during the magmatic-hydrothermal interaction. The hydrothermal fluid exsolved from deep magma brings abundant critical metals that are easy to migrate with fluid. Our study shows that stable metal isotopes, especially fluid-active metal isotopes, are very effective in tracing magmatic-hydrothermal processes and ore-forming fluid sources.
1
A study of the cyclostratigraphy and orbital forcing of the palaeoclimate changes in the Lower Ordovician Xialingnangou section, western margin of the Ordos Basin

makunyuan, tudan, gongyiming

Abstract: (3) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

The Ordovician was a crucial period for the evolution of life and the environment on Earth. During this period, there was a remarkable radiation of life known as the Great Ordovician Biodiversification Event, and the Earth""s climate shifted from a greenhouse in the Early Ordovician to an icehouse in the Late Ordovician. The Lower Ordovician Xialingnangou section in the Helan Mountains, western margin of the Ordos Basin, has excellent exposures of the Furongian to Middle Ordovician. The conodont biostratigraphy of Xialingnangou section provides valuable time constraints on the cyclostratigraphy. In this study, Ca, Fe, and Fe/Ca series were selected as palaeoclimate proxies to carry out cyclostratigraphical analyses on the Xialingnangou section. A continuous and high-resolution astronomical time scale of ~8.9 Myr was established based on the stable 405-kyr long eccentricity cycle, and the duration of the Tremadocian Stage was calculated to be 6.9 ± 0.28 Myr. The evolution spectra of the ratio of obliquity power and short eccentricity power to total power reveal a super-long obliquity cycle of ~1.2 Myr (s4–s3) and a super-long eccentricity cycle of ~2.4 Myr (g4–g3) in the Early Ordovician. Meanwhile, the sedimentary noise models of the tuned Ca, Fe, and Fe/Ca time series show high-resolution sedimentary noise fluctuations corresponding to sea-level changes. This reveals that sea-level changes were mainly driven by the super-long eccentricity cycle (s4–s3) in the early Tremadocian Stage, whereas in the middle Tremadocian to early Floian, they were mainly controlled by the super-long eccentricity cycle (g4–g3). The adjustment of the astronomical periods in the Early Ordovician may have played an important role in promoting the Great Ordovician Biodiversification Event.
1
Deep structure and interpretation of regional metallogenic model of the Dahongliutan pegmatite lithium ore deposit in western China

LI Wenyuan, ), GAO YongBao, RENGGuanLi, LUI Chen, LI Kan, KONGHuiLei

Abstract: (6) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

To reveal the deep structure of the granitic-pegmatitic type lithium and other rare metal mineral system, a Magnetotelluric (MT) survey was conducted in the Dahongliutan area of the Western Kunlun. Through 3D resistivity inversion of the MT data, two high-resistivity bodies were detected within the depth range of 0-20 km, reflecting the large-scale felsic magma and the partially concealed eastern granite basement of Dahongliutan. A widespread high-conductivity anomaly observed at depths of 20-80 km reflects the large-scale felsic magma reservoir formed by crustal remelting extending deep into the upper mantle. The mineralization host rocks, the granite basement of Dahongliutan, are shown to be rooted and represent a massive magma reservoir extending deep into the upper mantle, providing the source materials and heat for the formation of the giant Dahongliutan granitic-pegmatitic type lithium deposit. In comparison with the Songpan-Ganzi Jiajika super-large granitic-pegmatitic type lithium deposit, although the exposed granite in Jiajika is limited, the 3D resistivity inversion model of the MT data also reveals a widespread high-conductivity anomaly extending into the upper mantle, indicating the presence of a large-scale felsic magma reservoir. The difference lies in the shallower erosion depth in Jiajika, where the overlying granite intrusion has not been eroded. Therefore, Dahongliutan exhibits a "hot dome" feature with extensive granite outcrops resulting from deep erosional processes, while Jiajika represents a "gneiss dome" feature with the country rocks surrounding the granite subjected to thermal metamorphism. The giant ore belt of rare metal mineralization, including lithium, in Western Kunlun-Songpan-Ganzi, which hosts two super-large deposits of late Triassic age at its ends, is the product of large-scale crustal remelting and felsic magmatism. The saturation of H2O is a key factor in the exceptional enrichment of lithium and other rare metals in the granitic-pegmatitic type lithium deposits. Moreover, the "pre-enrichment" of lithium during different stages of differentiation and evolution in the felsic magma reservoir, intrusive granites, and pegmatites lays an essential foundation for the formation of massive granitic-pegmatitic type lithium deposits.
1
Petrogenesis and geological significance of the late Silurian quartz monzodiorite in the Dunhuang Block

Gan Baoping, Tang Juxing, Diwu Chunrong, Zhu Lihui, Sun Qingfei, Liu Yuanyuan

Abstract: (7) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

As a key microcontinental block/terrane in the southernmost Central Asian Orogenic Belt (CAOB), the genesis of early Paleozoic magmatism and tectonic evolution for the Dunhuang Block still remain poorly constrained, thus limiting the whole understanding of ocean-continental subduction-accretionary evolution of the southern Paleo-Asian Ocean (PAO) and the recycle of deep magmas materials. Here we have newly identified the Silurian quartz diorite from the Changshaliang area in the eastern Danghe reservoir in the central part of Dunhuang block, NW China. The petrology, zircon U-Pb dating, whole-rock geochemistry, and zircon Hf isotopes data have been carried out on the Changshaliang quartz monzodiorite. Zircon U-Pb dating results reveal that the quartz diorite was formed at ca. 428~426 Ma. Whole-rock analyses show that the quartz monzodiorite is relatively rich sodium (K2O/Na2O = 0.84~0.99), high Al2O3 (16.5~17.0%), Mg# (51.5~53.0) and low A/CNK (0.96~1.00) values, and point to the high potassium calc-alkaline metaluminous series. These samples studied exhibit negative Eu anomaly (Eu/Eu* = 0.70~0.77), enriched in larger ion lithophile elements (e.g., Rb, Ba, and Th), depleted in high field strength elements such as Nb, Ta and Ti, together with the low Y (16.3~19.0 × 10-6) contents and Sr/Y ratios (20.3~24.5), showing typical geochemistry characteristics of arc magma. Zircon Hf isotopes results indicate the Changshaliang quartz monzodiorites have a wide variable and negative εHf(t) value of -12.0 to -2.2, and older two-stage model age ranging from 2136 Ma to 1525 Ma. All the above features suggest that the Changshaliang quartz monzodiorites originated from melting of overlying mantle wedge metasomatized by subduction-related sediment melts, subsequently which triggered remelting of Paleoproterozoic lower crust materials. This study, combined with the existing research results, suggest that the Dunhuang Block was strongly involved in the orogenic events related to the southern part of the CAOB during the early Paleozoic period, which caused the modification and activation of crust, finally resulting in multi-stage magmatism events with different compositions resulted in significant activation crust. The block was at an active continental margin arc environment where the PAO continued to subducted to the Dunhuang Block.
1
The connected Yellow River first emerged during the Early Pleistocene, as evidenced by the findings from the Zhengzhou borehole in the North China Plain

LIN Xu, XIE Kejia, LIU Jing ), SONG Ruizhi, LIU Haijin, LI Qingkang, RE Liping

Abstract: (3) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

The formation of rivers is closely related to tectonic activities and climate changes. Therefore, studying the historical formation of rivers is crucial for comprehending the evolutionary processes of the Earth. The formation age of the Yellow River, the largest river in northern China, remains a subject of significant controversy. To address this issue, our study focused on the Kaifeng Depression, a crucial passage through which the Yellow River flows eastward into the sea. Through sedimentary drilling, paleomagnetic, magnetic susceptibility, grain size, and detrital zircon U-Pb age analysis, we obtained several noteworthy results. The drilling core at ZK02 penetrated the Quaternary strata, while the bottom of ZK04 was dated to approximately during the late period of the Early Pleistonece. The sedimentary environment at ZK02 was primarily fluvial, whereas ZK04 experienced a transition from fluvial and lacustrine deposition between 1.0 and 0.15 Ma to loess deposition from 0.15 Ma to the present. The analysis of detrital zircon U-Pb ages revealed that the main source of sediment in ZK04 between 1.0 and 0.15 Ma was the eastern Qinling Mountains. However, since 0.15 Ma, the sediment composition has been significantly influenced by loess from the Mangshan Mountains. In contrast, the sediment provenance of ZK02 is primarily connected to the evolution of the Yellow River. Material from the eastern Sanmen Gorge region has been present near Zhengzhou and the Yellow River Delta for at least 2.2 Ma. The connection between the upper, middle, and lower reaches of the Yellow River occurred between 1.9 and 1.6 Ma, mainly due to the humid climate conditions in the region. During the Middle Pleistocene, the Yellow River basin experienced a period of coarser sedimentation between 0.7 and 0.5 Ma, primarily driven by climate transitions. This period contributed to the formation of a distribution pattern similar to the current layout of the Yellow River and the Bohai Sea in North China. The presence of material from the Yellow River in ZK02 at 0.15 Ma indicates that the main channel morphology of the Yellow River has not experienced significant oscillations after flowing through this region since 2.2 Ma.
1
Tectonothermal evolution and of exhumation history of the fold-and-thrust belt constrained by the low-temperature thermochronology and analog models

Qianqian Feng, Nansheng Qiu, Tenger Borjigin, Hang Wu, Kangjie Long

Abstract: (6) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

Some time-temperature constraints are required to reconstruct the thermal history reconstructed by paleothermal indicators. The time-domain constraints limit the accuracy of the thermal histories. During the deformation process of the fold-and-thrust belt, differential horizontal slip occurs simultaneously with the uplift and cooling of the strata, resulting in differences in the uplift process. However, the thermal history, which revealed the cooling processes of the samples, did not consider the impact of flexural slip information, which has a significant effect on the structural analysis of a region with a long lateral slip distance. How to set appropriate time constraints to reconstruct the thermal history and accurately reveal the tectonothermal evolution of the fold-and-thrust belt is a scientific challenge in the field of low-temperature thermochronology research. In this study, a new thermo-kinematic approach that combines analog modeling, balanced reconstruction, various paleothermal indicators (low temperature thermochronology and maturity of organic matter) are used to constrain tectonothermal evolution of the eastern Sichuan fold-and-thrust belt, South China. This method accomplishes the fusion of “point-to-surface” and the quantitative coupling of overall-to-local analysis and meticulously dissecting the onset, pattern, rate, stage and size of uplift and exhumation during thrusting process. This study provides valuable insights regarding the restoration of tectonothermal evolution within the fold-and-thrust belt.
1
Multi-stage tectonic events constrained by apatite fission-track thermochronology in the Outang-Chuxian-Shangyaopu, Anhui Province

TIAN Pengfei, He Zifei, Lv Jinliang, He Yajie, YUAN Wanming, YANG Xiaoyong, DUAN Liuan

Abstract: (6) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

The Outang-Chuxian-Shangyaopu area in Anhui is located in the southeastern margin of the North China Craton, the northern margin of the Middle-Lower Yangtze River Ore Belt, the northern frontal belt of the Qinling-Dabie orogenic belt, and the east side of the Tanlu fault zone (TLFZ). The study area is located at the intersection and transition of various large-scale regional dynamical systems, and a large number of copper deposits are developed around it, which has important economic value. However, the degree of low-temperature thermal history research in the region is low, and the analysis of the thermal history of apatite fission track in this region is of great significance for understanding the regional tectonic evolution. We used apatite fission track to study the tectonic activities in the area of Outang-Chuxian-Shangyaopu. In this paper, we obtained nine apatite fission track results with central age between 113.2±7.8 Ma and 78.6±5.3 Ma. The study reveals the TLFZ has experienced multi-phase thermal events. The Outang-Chuxian-Shangyaopu area showed rapid exhumation at 130~100 Ma, possibly related to the high-speed oblique subduction of the Izanagi plate. The exhumation of the study area was relatively slow from ~100 Ma, until ~60 Ma when the far-field effect of the Indian plate and the Eurasian plate was reflected in the Outang-Shangyaopu area. After the hard collision between the Indian plate and the Eurasian plate started, the Outang-Shangyaopu area was exhumated rapidly. Especially, the thermal history clearly reflects the impact of the hard collision between the Indian and Eurasian plates (55~52 Ma) on the thermal history of the study area, and then the study area was controlled by two tectonic systems, which are the subduction of the Pacific plate and the long-range effect of the collision between the Indian plate and the Eurasian plate.
1
River Terrace characteristics in the Wuhai Broad Valley at the upper reaches of the Yellow River and their implications for Landform Evolution

LIU Xiaobo), LI Rongxi), QUAN Cheng, WU Xiaoli), ZHANG Haoying), CAO Pengju)

Abstract: (9) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

The formationof the Wuhai Broad Valley（WBV）, located at the junction of the Yinchuan Basin and the Hetao Basin, is a visual record of the historical evolution of the end of the upper reaches of the Yellow River.. However, the stratigraphic- -chronological sequence of the Yellow River terraces in this section has not yet been established, and the formation and cutting history of the Yellow River in this area is still unclear. In this paper, based on the field geomorphological, stratigraphic, and sedimentologic investigations, four-level of fluvial terraces are identified on the east side of the WBV and are dated by the Optically Stimulated Luminescence (OSL) dating method. The results show terrace T1 is a depositional terrace with an abandoned age greater than 0.52±0.04 ka. The terraces T2-T4 are base terraces and are characterized by a similar sedimentary sequence consisting of fluvial deposits in the upper part and lacustrine deposits in the lower part. The maximum estimated abandon ages of the terrace T2, T3, and T4 are about 41.98±2.7 ka, 67.48±4.07 ka, and 102.32±6.00 ka, respectively. The average incision rates from T4 to T3, T3 to T2, and T2 to T0 are calculated to be 0.11 mm/a (~102-67 ka), 0.24 mm/a (~67-42 ka), and 0.26 mm/a (42 ka-modern), showing a gradual increase incision rate since ~102 ka. The age of the lacustrine deposits in the terraces T2-T3 coincides with the development time of the Late Pleistocene “Jilantai-Hetao Megalake”, indicating that the range of megalake had already reached the study area at that time. The formation of the fluvial terraces in the study area was developed in the process of narrowing and disappearing of the “Jilantai-Hetao Megalake”, which represents the transition between lake-river landform at the upper reaches of the Yellow River in the Late Pleistocene. Through detailed comparisons with the low-level sequences of various fluvial terraces around the Ordos Block, combined with regional tectonic and climatic information, it is concluded that the formation of the Late Pleistocene fluvial terraces in the WBV and the transition between lake-river landform were mainly controlled by tectonic activities.
1
The genesis and tectonic significance of the Xinchang granites in Beishan, Gansu Province and its implications for the geological disposal of High-Level Radioactive Wastes (HLWs): Constraints from geochemistry, zircon U-Pb chronology and Lu-Hf isotopes

GUI Rengao, WANG Ju, SUN Jia, SHI Kaituo, XIAO Wenzhou, ZHOU Miao, ZHANG Xiaoping, LI Nan, WU Peng, DUAN Xianzhe

Abstract: (9) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

Xinchang, located in the eastern section of the southern part of Beishan, Gansu province, is a key area for studying the tectonic evolution of the southern part of Beishan and evaluating the site selection in the geological disposal of HLWs. The Xinchang granitoids are composed of three lithofacies units: medium-fine biotite monzonitic granite, granodiorite and gneissic tonalite. Biotite monzonitic granite and granodiorite are generally rich in silicon, potassium (K2O>Na2O), and alkali, and have medium aluminum. These two granites belong to weak peraluminous and high potassium calc alkaline A2 type granite. The tonalite is rich in sodium (K2O
1
Microstructure and composition of the small shelly fossils in Cambrian Meishucun stage phosphorite rock, Central Guizhou: constraints on biological phosphorus formation

Peng Rou, Yang Ruidong, Gao Lei, Gao Junbo, Chen Jiyan, Gao Chuanqian

Abstract: (11) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

The identification of the microstructure and shell composition of small shelly fossils are of great significance for revealing the evolution of the early Cambrian small shelly fossils, and a large number of small shelly fossils have been preserved in the early Cambrian Meishucun stage’s phosphorite rock in Central Guizhou, but there were few studies on the microstructure and composition of small shelly fossils in the past. In this paper, the microstructure and shell composition characteristics of small shelly fossils in Zhijin Xiongjiachang and Qingzhen Luohang phosphorite rock in Guizhou Province were analyzed by electron microscope and scanning electron microscope (SEM-EDS) to observe and test individual small shelly fossils in rock thin sections and acid-treated small shelly fossils. The results showed that the diversity of small shell fossils and their shell composition in the phosphorite rock of Zhijin and Qingzhen were consistent, mainly Hyolitha, and their components were fluoroapatite elements such as P, Ca, F, and O. The small shelly fossils preserves obvious nano-scale apatite mineralized particle skeleton, multi-circle structure, dissolved pores and tube nesting. In addition, the insitu micro-element surface scanning of the small shelly fossils was carried out by electron exploration, and it was found that the main elements P and Ca were distributed in the small shelly fossils and their fragments, and the cementation almost did not contain P elements. At the same time, the content of small shelly fossils (including fossil fragments) in the whole rock was inferred by the help of thin-slice full-glass surface scanning, which was positively correlated with the phosphorus content in the phosphorite rock, and it was believed that the prosperity of small shelly fossils in the Cambrian Meishucun stage had an important contribution to the formation of phosphorite rock in the same period.
1
Banded iron formation: Advances and challenges in Cyclostratigraphy

BAI Yang, MA Kunyuan, ZHANG Lianchang, WANG Changle

Abstract: (11) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

Banded iron formation (BIF) is chemical marine sedimentary rock that was exclusive to the Precambrian. They constitute a significant component of early crust and provide valuable insights into the tectonic evolution, ancient environmental changes, and primitive life activities on early Earth. BIF exhibits distinctive rhythmic band at various scales. Despite considerable progress in understanding the sources of ore-forming materials and depositional conditions of BIF, ongoing debate persists regarding the formation of bands at different scales. In recent years, geologists have identified numerous reliable Milankovitch cycles records within BIF stratigraphy, leading to innovative theories proposing astronomical forcing as a driving factor for the formation of diverse rhythmic bands in BIF. This paper presents a comprehensive review on cyclostratigraphy in BIF, with specific focus on exploring the impact of climate change driven by Earth's orbital parameters on BIF. Furthermore, this study presents key unresolved issues and explores future prospects for cyclostratigraphic studies on BIF in the North China Craton.
1
The basement dipping’s control on the structural deformation of the Longmenshan thrust belt

Yu Jingqiang, zhao li, Zhang Yunyin, Dong Dawei, Yu Zhengjun, Wang Yongshi, Zhang Pengfei, Wei Wen

Abstract: (8) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

The basement dipping is an important factor controlling the structural deformation of thrust belts. However, rare attentions have been paid on the basement dipping characteristics of the Longmenshan thrust belt. Based on interpretations of seismic profiles, this paper found that the Longmenshan thrust belt in the northern, central and southern segments underwent different basement dipping. The basement dipped 2.6° toward foreland in the northern because of the uplift of thrust sheets. The basement dipped 3.2° toward hinterland in the central due to several phases of loading. The basement dipped 2.6° toward hinterland in the southern which was the result of earlier rifting and later loading. The numerical experiment shows that the basement dipping toward hinterland or horizontal subsiding will suppress the forward propagation of thrusting deformation, and superimposed the thrusting sheets. While the control effect of the pre-existing basement dip is opposite. When the basement remains horizontal or dip toward the foreland, the thrust sheets in hinterland uplifted stronger than that of the foreland, which will cause the basement dipping toward the foreland as a whole. When the basement dipped backward with syn-sedimentation will result in the back-thrusting in slope zone. Numerical simulation proved the basement evolution in southern segment of the Longmenshan thrust belt. Before the Late Cretaceous, it was in an extensional regime with thick strata in the west and thin strata in the east, and its basement dipped to the west. During the Late Cretaceous—Eocene, a foreland basin developed, and the basement dipped toward hinterland because of the loading. During the Oligocene—Miocene, the thrusting deformation strongly propagated into the basin, and the basement almost had no dipping. Since the Pliocene, the basement in hinterland has been uplifted because of the Qinghai-Tibet Plateau, which resulted in the sharp topography.
1
Numerical Simulations Reveal the Control of Lithospheric Strength Structure on Passive Continental Margins’ Evolution

Fan Qingkai, Guo Jinrui, Gao Min, Wu Gaokui, Wang Yanyang

Abstract: (5) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

The formation and evolution of passive continental margins are controlled by the pre-rifting lithospheric strength and its vertical structure. In order to investigate the effect of two factors on lithospheric breakup time, faulting styles, sizes and morphology of passive continental margins, we define two comprehensive indexes as integrated lithospheric strength (σe) and crust-mantle rigid layers coupling degree (Coc), and reveal the influences through geodynamic numerical modelling. According to simulations, the strength structure of lithosphere plays a key role in controlling its rifting duration, a stronger pre-rifting lithosphere inevitably causes a longer lasting rifting, and on this basis, the decrease of the Coc will prolong this process further. For the fully coupling lithosphere (Coc=1), upper crust usually breaks first, and will form symmetric margins through a ‘pure-shear’ mode. When Coc decreases, rigid layers of upper crust and upper mantle deforms separately, and an asymmetric continental margin will form by lateral migration of the rift center. Under such circumstances, the upper mantle with a relatively limited thickness will break first, while when a thick upper mantle develops, the upper crust will break first and lead to the exhumation of mantle rocks. In addition, a low Coc is necessary to generate large-scale passive continental margin basins with a broad and gentle geometry, and the lower Coc is, the greater the migration distance of the rift center and the conjugated margins are. Thickening of the crust will lead to the decreasing of Coc, which will also enlarge the scale of continental margins. Those understandings can be verified on the central segment of South Atlantic continental margins.
1
Metallogenic regularity and model of Paleogene-Neogene anticlinal fissure pore brine in central and western Qaidam Basin

Han Guang

Abstract: (8) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

In recent years, deep fissure pore brines have been found in Paleogene-Neogene anticlinal tectonic strata in the central and western Qaidam Basin, Qinghai Province. These brines have large reservoir thickness, high content of potassium, lithium and boron resource elements, and some metallogenic conditions have reached the boundary or industrial mining grade, which have great potential for further prospecting. In this study, the sedimentary and salt-forming evolution of Paleogene-Neogene strata, reservoir characteristics and element geochemistry of brine deposits in Qaidam Basin are reviewed in detail, and the spatio-temporal metallogenic characteristics and genetic mechanism of brine resource elements are summarized. The results show that the reservoirs of brines in the west of the basin are gray mudstone and mudstone, while in the central of the basin are mudstone and siltstone. The content of potassium, lithium and boron resources gradually decreases from the west (Shizigou -Nanyishan) to the central (Hongsanhan - Yanhu) and to the north (Eboliang - Lenghu - Nanbaxian), which is closely related to the migration and evolution of the sedimentary center of the ancient lake basin. The metallogenic model of the Paleogene-Neogene anticlinal fissure pore brine deposit is established, which has a good guiding significance for future exploration evaluation and metallogenic prediction.
1
Petrogenesis of granites and its relationship with uranium mineralization in the Xiazhuang pluton, northern Guangdong Province: Constraints from zircon trace element and mineral chemistry

TAO Jihua, Zhang Zefeng, Renzhi, XU Zhitian, SUN Junjie, CAO Jun, SU Xianyuan, LENG Chengbiao, XU Deru

Abstract: (7) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

The granite-hosted uranium deposits in South China are spatially associated with the U-rich granites (U﹥10×10-6). Understanting the petrogenesis of these uranium-bearing granites with high U contents is not only significant for formulating exploration strategies for granite-hosted uranium deposits in South China, but also for ta better insights into the mechanism of U enrichment and mineralization for the granite-hosted uranium deposits. Here we investigate the Xiazhuang garnites which represent typical U-bearing granites with high U contents, using zircon U-Pb dating and zircon trace elements, biotite and chlorite geochemistry data, to constrain the petrogenesis and its relationship with uranium mineralization. LA-ICP-MS zircon U-Pb dating shows that the Xiazhuang granites were emplaced 234~236 Ma. The parental magmas of Xiazhuang granites were derived from the partial melting of Paleoproterozoic metasedimentary rocks with high F contents, and then underwent relative highly degree of magma differentiation. The oxygen fugacity decreased and U contents increased with the magmatic evolution, which led to the formation of U-rich granites (U﹥10 ×10-6) containing a large amount of U-rich accessory mineral such as uraninite, monazite, xenotime and thorite. Our study suggests that the U-rich accessory minerals in Xiazhuang granites were altered by the hydrothermal fluids in relatively acidic and oxidizing conditions in response to the Yanshanian mafic magmatism, followed by uranium leaching during alteration and provided uranium sources for the uranium mineralization.
1
Geology, geochemistry and of the Chakeng copper-potash feldspar deposit in Dehua district, Fujian province，and a preliminary discussion for its genesis

Zhang Chengjie, Qiu Tian, Xiong Fahui, Wen Wu, Mu Xiaoping, Chen Qin

Abstract: (0) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

The Chakeng copper-potash feldspar deposit (236 t Cu and 41.52 wt potash feldspar), located in the central part of polymetallic mineralization concentrated area of Mesozoic magmatic belt along southeast coast, is hosted in Qiongxi biotite granite in Dehua district, Fujian province. Copper ore bodies and potash feldspar ore bodies are the mainly two kinds of orebody in this deposit, both of which are controlled by a group of NNE trending faults F1, F2 and F3, and their secondary faults. The ore-forming process consists of three stages: potassic metasomatism (I); silicification and muscovite alteration (II) and carbonatization (III). Stage I and II are the major period for potash feldspar and Cu mineralization, respectively. Cu mineralization is strictly superimposed on potash feldspar mineralization, forming Cu- and potash feldspar-rich ores. Based on the geology, mineral chemistry, whole-rock geochemistry and internal structure of zircon, we propose that the Chakeng deposit is a hydrothermal-metasomatic deposit. Magmatic zircons separated from the copper-potash feldspar ore were probably captured/inherited from Qiongxi granite by hydrothermal fluids. Zircon U-Pb dating yielded a concordant age of 159.4±1.0 Ma (MSWD=0.21), which is interpreted as the petrogenic age of Qiongxi granite, and also defined as the upper limit of ore-forming age. Granite porphyry, intruded in biotite granite in Chakeng area, is characterized by enrichment of Ba, Sr, P, Ti, Pb and Cu, which is similar with the copper-potash feldspar ore but much higher than biotite granite. It is inferred that the copper-potash feldspar mineralization possibly resulted from the evolution of granite porphyry in this area.
1
The U-Pb isotope dating and tracing using different accessory minerals in pegmatite: Problems and application

Jiang Shao-Yong, ZHANG Haoxiang, LIU Siqi, LI Wentian, YIN Yanliang, CHE Yuying, SU Huimin

Abstract: (10) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

Dating and tracing have always been key scientific issues in the study of pegmatite petrogenesis and mineralization processes, as well as rare metal enrichment mechanisms. Accessory minerals are not only important carriers of rare metals and rare earth elements in pegmatites, but also contain abundant other trace elements such as high U-Th content, making them an ideal probe for studying pegmatite chronology, petrogenetic and mineralization processes, and to trace the magma sources. The accessory minerals that are commonly used for U-Pb dating in pegmatites include zircon, columbite-tantalite, monazite, cassiterite, titanite, allanite, xenotime, and apatite. Due to differences in closure temperature, mineralogical characteristics, and elemental behavior in fluids with different properties, U-Pb isotope systems of different accessory minerals in pegmatites often exhibit complex age spectra, which may record potential late geological processes in pegmatites, such as auto-metasomatism, late metamorphism, and fluid alteration. Therefore, based on previous studies on mineral microstructures such as optical microscopy, scanning electron microscopy, cold cathodoluminescence, and laser Raman spectroscopy, in-situ U-Pb dating and geochemical analysis of major and trace elements and isotopes of accessory minerals from different generations of pegmatites are carried out, which is beneficial for a comprehensive understanding of the evolution history of multiple geological events and pegmatite petrogenesis and mineralization processes. It is of great scientific significance to construct an accurate spatiotemporal framework of tectonic-magmatic-hydrothermal mineralization events related to pegmatite formation.
1
Zircon U-Pb Ages and Its Geological Significance of Ediacara-Cambrian tuff from Guizhou, South China

Jinhong Xu, Chengquan Wu

Abstract: (15) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

The Dengying Formation and Laobao Formation are important Ediacaran-Cambrian stratigraphic units in South China. We report here integrated zircon cathodoluminescence (CL) and U-Pb isotopes of tuff from the platform facies in the Xinzhai section located in the Yankong area of northern Guizhou, and Jianfengding and Wangjianshan sections located in the Songlin area of northern Guizhou, and from the transition zone in the Niujiaochong and Xinchong sections located in the Pianyan area of eastern Guizhou, and from the slope facies in the Guabang section located in the Sanshui area of southeast Guizhou. Zircon LA-ICP-MS U-Pb dating results show that the tuff layers of Xinzhai, Wangjianshan and Xinchong sections were formed at 532±4 Ma, 536±5 Ma and 535±4 Ma, respectively, and the tuff layers of Jianfengding, Niujiaochong and Guabang sections were deposited at 520±4 Ma, 517±3 Ma and 521±3 Ma, respectively. Synthesis of previous results and this study show that the deposition time of the Dengying Formation and Laobao Formation are constrained from 551.1±0.7 Ma to 518±5 Ma, and 550.6±3.3 Ma to 517±3 Ma, respectively. Which belong to simultaneous heterogeneous sedimentation. The uranium-rich phosphorite within the Laobao Formation and equivalents in the Yankong, Songlin and Pianyan areas were formed between 546.3±2.7 Ma and 532±4 Ma, 536±5 Ma to 520±4 Ma and 535±4 Ma to 517±3 Ma, respectively.
1
Late Cretaceous eolian sandstones in southern Hunan province: Indicative of paleo- environment and climate

LI Xianghui, WANG Jingyu, ZHENG Chenyu, LIU Ruicen

Abstract: (18) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

As a climatic proxy, eolian sandstones have been applying in the paleoclimatic analysis. For the Late Cretaceous eolian sandstones in South China, lithofacies and paleoclimatic indications have been deficient, while paleowind system has been dispute in the paleowind directions. In this study, we conducted integrating analyses of lithofacies, texture, and paleowind directions for the eolianites from the Honghuatao Formation of the Changsha Basin, Li-You Basin, and Cha-Zi Basin, middle-southern Hunan. Results show that sandstones are orange-red and brick-red with large and high-angle cross-beddings, in which laminal set is often 3?10 m thick, even up to ~20 m; detrital grains are dominated by fine sand with medium-good roundness and sorting; reddish brown and / or dark brown Fe-varnish are common along the quartz edge; impact scars of dish-, V-, and crescent- shape generally occur on quartz surface; sandstones are characterized by grain-supported and Fe-mud matrix textures; and main surfaces of reactivation surfaces (R), interdune migration surfaces (I), and superimposition surfaces (S) bound the dunes. They together indicate the sandstones of the Honghuatao Formation are eolian in origin. These eolianites had been built onto the underlain Luojingtan alluvial fan conglomerates and both laterally interfinger out each other. The alluvial fan lithofacies is featured by pulse debris and muddy gravity current sediments, manifesting arid alluvial type. Eolian sandstone and associated arid alluvial fan lithofacies suggest the (semi-) arid climate, possibly in a relative cooling condition. Low distribution in basin and association with proximal-source alluvial fan facies indicate the Late Cretaceous eolian sandstones have been accumulated in an intermontane dune environment rather than in a sand-sea desert. Two sets of paleowind directions SE and NE are predominantly recognized from the eolian sandstones, which are not compatible with those of modern planetary wind system. It is proposed that they two sets of prevailing wind directions might be a superposition imprints of modern planetary, East Asia monsoon, and local reflection-refraction wind systems.
1
Lithology identification of Karamaili ophiolite belt in Xinjiang based on ASTER and SDGSAT-1 thermal infrared data

Liulei, Zhang Zhao, Zhang Qunjia, Mei Jiacheng

Abstract: (22) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

Thermal infrared spectrum (TIR, 7-14 μm) has unparalleled advantages for the identification of rock-forming minerals, but currently there are few available satellite borne thermal infrared data sources, and the spatial and spectral resolution of the images is generally low. The thermal infrared spectrometer (TIS) carried by China's Sustainable Development Scientific Satellite-1 (SDGSAT-1), which will be launched in 2021, is characterized by large bandwidth (300 km), high spatial resolution (30 m), and high detection sensitivity, and has a better application prospect in lithologic mapping. In this study, two kinds of thermal infrared images, ASTER and SDGSAT-1, were selected from the East Junggar Kalamari region of Xinjiang to establish rock indices of mafic–ultramafic rocks, quartz-rich rocks, feldspar-rich rocks, and granitoid rocks, and combined with the results of the principal component analysis to analyze the distribution characteristics of the different rock types in the 2D and 3D feature spaces, and constructed the lithology identification models of the two kinds of data in the multi-dimensional spectral feature space, respectively. The results show that: 1) The rock indices constructed from ASTER TIR and SDGSAT-1 TIS data can effectively identify mafic–ultramafic rocks, quartz-rich rocks, feldspar-rich rocks and granites, with an overall accuracy of 95.16% and 98.02% for lithology identification, respectively; 2) The multi-dimensional spectral feature space model constructed with two types of data also has good lithology recognition performance, with overall accuracy improved to 96.78% and 98.54%, respectively; 3) SDGSAT-1 TIS has improved the accuracy of extracting mafic-ultramafic rocks by 13.26% compared to ASTER TIR, and has stronger recognition ability for rocks with smaller outcrops. It has great potential for application in lithology mapping.
1
Computational Grid Selection in numerical modeling of Subduction Dynamics

yangshaohua, PAN Jiawei, LI Haibing

Abstract: (17) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

Various numerical models based on mathematical physics equations in geosciences, including numerical modeling of subduction dynamics, necessarily involve computational grids consisting of discrete nodes, which control the accuracy of numerical calculations and thus the credibility of numerical models in solving practical geoscientific problems. The numerical modeling of subduction dynamics has made great progress in recent years; however, the numerical accuracy due to the arbitrary use of computational grids is still unclear. In this paper, we construct numerical models based on three sets of computational grids with different accuracies for a classical scientific problem, and evaluate the possible impact of low-precision grids in practical research. It is argued that the computational grid with an accuracy of 2km×2km for the encrypted zone, which has been more commonly used in the last decade, is likely to obtain computational results containing significant numerical errors, which in turn affects the application of numerical modeling in subduction dynamics. Therefore, it may be necessary to revisit models with low precision grids and their corresponding geologic conclusions in recent years. As numerical models of subduction dynamics become more and more highly nonlinear, the choice of computational grids with the highest possible accuracy may be inevitable. For the case of using low-precision grids for highly nonlinear problems, definitive evidence of grid reliability is needed. We propose a new set of grid pattern suitable for subduction dynamics: locally encrypted structured quadrilateral grids containing hanging nodes. This grid may accomplish high-precision numerical calculations with a small total number of grids and is relatively simple to implement.
1
Palynoflora from the Lower Jurassic Fuxian Formation in Ordos Basin and its response to the Jenkyns event

WEI Yi, NAN Qingmin, YANG Bing, ZHANG Xinzhi, SUN Siyuan, SU Guifen

Abstract: (18) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

For researching the influence of Jenkyns event on the paleoclimate of inland basins, we analysis the palynological characteristics of Fuxian Formation in the southern Ordos basin. Three palynological assemblage were divided from bottom to top as: Cyathidites-Deltoidospora-Chasmatosporites assemblage, whose age is the Pliensbachian of early Jurassic; Classopollis-Quadraeculina-Chasmatosporites assemblage, whose age is the early-mid Toarcian of the early Jurassic, which coincides with the Jenkyns event; Cyathidites-Cycadopites-Psophosphaera assemblage whose age is the late Toarcian of early Jurassic. The paleoclimate reflected by sporopollen community shows that the Ordos basin experienced the transformation as subtropical humid climate→subtropical semi-humid and semi-arid climate→subtropical humid climate during the early Jurassic Fuxian period. Different from the previous conclusions of the Tethys Oceanic and Pan-Oceanic studies, the Jenkyns event appears as a drying and heating event in the Ordos Basin (the hinterland of Eurasia).
1
Identification of the Central Fault— the extension of the Red River Fault Zone in the Yinggehai Basin

Fu Yongtao, Chen Guanfei, Wu Tao, Wang Wanying, XuTao, Zhou Zhangguo, Yang An

Abstract: (27) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

The early left-lateral and late right-lateral strike-slip shearing of the Red River Fault Zone performes a crucial function in controlling the tectonic evolution and sedimentation processes of the Yinggehai Basin. While the Red River Fault has been identified in the northern and southern parts of the Central Depression of the Yinggehai Basin, it remains unclear how the Red River Fault Zone extends within the Central Depression, impacting the study of the basin's tectonic evolution and sedimentation processes. Current studies on the tectonic evolution of the Yinggehai Basin are based on the No. 1 Fault on the eastern side and the Yingxi Fault on the western side as boundaries. In this paper, utilizing satellite altimetry gravity anomaly data in the Yinggehai Basin and employing the normalized vertical derivative total horizontal derivative edge recognition (NVDR-THDR) method, we determined the distribution of the Central Fault. This recognition is verified by 2D seismic sections in the northern and central parts of the Central Depression. The Central Fault is the extension of the Red River Fault Zone in the Yinggehai Basin, developing as a left-stepping fault system north of the Dongfang Diapir area, forming an eastward dislocation in plan view. In the Changnan Diapir area, it consists of several parallel faults. In the Ledong Diapir area, a left-stepping sinistral strike-slip fault system is developed, leading to the development of the Ledongnan Subsag (pull-apart basin). Seismic profiles reveal that the buried depth of the Central Fault is larger in the Central Depression, with a two-way travel time exceeding 6 s. According to the stratigraphic sequences, the main active period of the Central Fault predates 30 Ma to 15.98 Ma. The Cenozoic sediment thickness of the Yinggehai Basin, calculated using the fast inversion method of the double-interface model of the gravity field, reveals the development of five depocenters with thicknesses exceeding 15 km in the Central Depression. Generally, to the west of the Central Fault are the depocenters, while to the east, there is a gradient zone with smaller sediment thickness. Simultaneously, the five diapir belts in the Central Depression are all distributed to the west of the Central Fault, with the left-stepping sinistral strike-slip fault system in the Ledong diapir area exerting significant control on three parallel diapir belts. The Central Fault holds great significance for the tectonic evolution and oil and gas exploration in the Yinggehai Basin.
1
New insight into the mechanism of No. 1 fault in the Yinggehai Basin: analogue modelling and discussion

Xiao Kunze, Tong Hengmao, Yang Donghui, Li Xuesong, Li Xushen, Cui Hao

Abstract: (13) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

The Yinggehai Basin has long been of great interest to academics and the petroleum industry due to its special tectonic location (the area of the Red River Fracture Zone into the sea) and its abundant natural gas resources. Since the Indo-Eurasian collision-extrusion model was proposed to explain the deformation in Southeast Asia, the Yinggehai Basin has been regarded as a typical pull-apart basin. However, based on the generalised fault theory, and through the structural analysis of the 3D seismic data system, they revealed that the tectonic features and the distribution of fault distances of the boundary fault (No.1 fault) in the Yinggehai Basin are not similar to those of the traditional strike-slip faults, but they are also strongly similar to the features of the structural deformation under oblique extension. Furthermore, our article proposes a new insight into the mechanisms of the No. 1 fault based on the analysis of the structural features of the No. 1 fault and also combined with the analogue modelling. The results show that the No.1 fault has obvious characteristics of an oblique-slip normal fault, and there are significant differences in the amount of strike-slip and dip-slip displacements in different areas along the fault strike, as well as the control of sedimentation in the basin. The boundary fault was an oblique-slip normal fault due to the reactivation of pre-existing structures under a north-south extensional stress regime during the Oligocene-Miocene period, and these r insights were also verified by analogue modelling. A new insight into the mechanism of the No. 1 fault, which theoretically reveals the mechanism of the Yinggehai Basin and can provide guidance for the structural analysis of the Yinggehai Basin and its later oil and gas exploration and development.
1
Numerical simulation of co-seismic deformation and seismicity following the Pingyuan M5.5 earthquake in Shandong Province on August 6, 2023

Meng Qiu, WANG Zitao, ZHANG Huai

Abstract: (19) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

On August 6, 2023, M5.5 earthquake occurred in Pingyuan County, Dezhou City, Shandong Province, causing significant economic losses and ending the nearly 40-year period of M≥5.0 seismic quiet in Shandong Province. The epicenter of the Pingyuan earthquake is located in a densely populated area, with rapid economic development. The changes in regional seismicity resulting from this earthquake and the potential for future strong earthquakes are significant social concerns. We use the finite element numerical simulation with a three-dimensional model to study the co-seismic deformation and stress changes in the seismogenic environment at the epicenter and its surroundings. Additionally, we utilize the assumed rupture model to simulate the co-seismic dislocation. Based on the Coulomb stress change theory, we investigate the seismicity changes in the surroundings. The results indicate that the primary deformation caused by the earthquake is concentrated within 10 km of the seismogenic fault, and the Coulomb failure stress at the epicenter decreases by more than 500 kPa. The probability of a strong earthquake occurring is low in the near future. The Pingyuan earthquake has a significant impact on the seismicity in the surroundings. It may increase the occurrence of slip-type small and medium earthquakes in the north, while reducing the occurrence of normal fault-type earthquakes in the west. Longer seismic data and more comprehensive research are still needed to understand the seismicity changes in the North China Plain and its adjacent faults.
1
Zircon U-Pb ages and Rubidium occurrence of the giant Gariatong granite-type rubidium deposit, Tibet

XIE Jinling, TANG Juxing, LIN Bin), TANG Pan, QI Jing, DENG Shilin, HE Liang, ZHANG Xiaoxu

Abstract: (9) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

Lots of highly differentiated granites are widely distributed on the Qinghai-Tibet Plateau, but their mineralization and exploration potential for rare metals were unclear. The Gariatong deposit is a newly discovered giant granite-type rubidium deposit in the central Lhasa terrane, recently. The detailed geological survey and borehole logging of the Gariatong deposit revealed that the rubidium mineralization is mainly hosted in monzogranite and surrounding rocks. Zircon U-Pb dating results show that the weighted average ages of the ore-bearing monzonite is 20.0±0.5 Ma (n=14, MSWD=1.8), which suggested that the intrusion occurred in the Miocene. Detailed petrography and electron microprobe analyses revealed that rubidium is mainly host in muscovite and biotite in an isomorphism form, and no independent rubidium minerals are seen. The geochemical characteristics of muscovite and biotite revealed that the magma associated to mineralization is the product of remelting of crustal-derived material in a low-oxygen fugacity environment, and the formation of fluoride-rich magmatic hydrothermal fluids after strong differentiation is the key to the formation of large-scale rubidium mineralization. The discovery of the giant granite-type rubidium deposit in the Gariatong not only enriched distribution of rubidium mineral resources in China, but also support the prospecting of rare metals in highly differentiated granites on the Qinghai-Tibet Plateau.
1
Enrichment process of rare earth elements in Permian sedimentary manganese carbonate deposits from the Zunyi area, northern Guizhou

Xu Hai, Gao Junbo, Yang Ruidong, Xu Jinhong, Liu Zhichen, Qiao Wenlang, Ye Fei, Zhang Xu

Abstract: (28) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

As strategic and critical minerals, rare earth elements and yttrium (REY) have long been of great concern. In recent years, previous studies have reported that numerous sedimentary manganese (Mn) ores are significantly enriched in REY (> 500x10-6). However, the provenance, carrier, and enrichment process of REY in sedimentary Mn ores still lack precise constraints. It is noteworthy that the significant enrichment of REY in the Zunyi Mn deposits has been discovered through careful compositional analysis. Specifically, the average ∑REY content in the ores and the underlying tuffaceous clay is 693.97×10-6 and 1464.54×10-6, respectively, which is mainly characterized by the enrichment of La, Ce, Nd, and Y, and is the first reported REY-bearing carbonate Mn deposits in China. The macro and micro mineralogical composition, symbiotic and intergrowth relationships, and REY differentiation highlight that the enrichment of Mn and REY primarily originates from the magmatic-hydrothermal system of the Emeishan Large Igneous Province (ELIP). The REY in ores and tuffaceous claystones mainly occurs as monazite, xenotime, and goyazite, which indicates that phosphate is the main carrier of REY in Zunyi Mn deposits. Of note, monazite and xenotime are mainly fine-grained (<10μm) anhedral particles form, coexisting with authigenic minerals (e.g., rhodochrosite and capillitite), and closely symbiosis with residual Fe-Mn oxides and altered tuffs in rhodochrosite. Meanwhile, goyazite appears in microcrystalline or colloidal form, closely symbiosis with fine-grained minerals (e.g., illite and quartz), and locally coexisting with residual altered volcanic debris. In conclusion, we suggest that REY enrichment is controlled by ELIP paleostructure-magma-hydrothermal activity, multiple carriers, and multiple sedimentary stages, therein REY initially occurs in Fe-Mn oxide and tuff, subsequently transfer to phosphate minerals during early diagenesis-alteration process.
1
Organic-matter-rich tentaculitid shales of the Devonian in the region from the southern Guizhou to central Guangxi province of South China: An importantly potential target rock for shale-gas exploration

MEI Mingxiang, Cen Wenpan, Muhammad Riaz

Abstract: (12) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

The Devonian is a special geological time that was marked by an episode of Earth history noteworthy for the global deposition of organic-matter-rich shales. Within an inter-platform basin facies that is dominated by deep-water deposits in the region from the southern Guizhou to the central Guxngxi, a set of organic-matter-rich tentaculitid shales with the thickness of more than 600 meters was relatively concentrated and developed from the Emsian Age to the Frasnian Age of the Devonian. Following features not only characterize this set of organic-matter-rich tentaculitid shales but also demonstrate it is an importantly potential target rock for shale-gas exploration: 1) a relatively higher total organic carbon (TOC) value of more than 2% that can be up to 5% to 6%; 2) From the Amsian Age of the early Devonian to the middle Devonian, organic carbon content is typically enriched in massive organic-matter-rich tentaculitid shales with the monolayer thickness of more than 100 meters that is formed in the period of third-order relative sea-level rising, and depleted in the calcareous shales and muddy limestones of the shelf facies forming in the period of third-order relative sea-level falling; and 3) Within the Liujiang Formation that is dominated by silicalites of the Frasnian Age of the late Devonian, organic carbon content is typically enriched in massive organic-matter-rich tentaculitid shales with the monolayer thickness from 30 to 40 meters that is formed in the period of third-order relative sea-level falling, and depleted in silicalietes of the pelagic basin facies forming in the period of third-order relative sea-level rising. It can be certain that the accumulation of organic matter within organic-matter-rich tentaculitid shales in study area is controlled by complicated, nonlinear interactions among the three factors: productivity, preservation, and sedimentation rate. More particularly and importantly, the high-density preservation of tentaculitid fossils demonstrates that the accumulation of organic matter within organic-matter-rich tentaculitid shales in study area is genetically related to the biological carbon pump of zooplankton.
1
Late Triassic extension in the northwest Ordos Basin: Constraints from Langshan basalts, NW China

huijie, fanliyong, zhaoweibo, kangrui, wangyufei, zhangjin, zhangbeihang, zhaoheng

Abstract: (16) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

This study reported newly discovered Triassic basalts in the Langshan region, analyzed its tectonic setting and contemporaneous deformation, and discussed the characteristics of the Late Triassic basin in the northwest margin of Ordos Basin. 40Ar/39Ar geochronology show that the basalts formed in the Late Triassic (217 Ma). Whole-rock geochemistry reveals that the basalts have OIB affinity, derived from the 5–10% partial melting of garnet and spinel lherzolite, formed by the decompression melting of the asthenosphere in the intraplate extensional setting. The Langshan region also developed a Late Triassic NE-SW trending ductile sinistral shear zone, which connected southward with a simultaneous sinistral shear zone in the Bayanwulashan and Helanshan regions and extended northward into Mongolia. Temporal simultaneity indicates the close relationship between sinistral shearing and basalts eruption. By comparing the contemporaneous basalts, Yanchang Formation, and sinistral strike-slip faults in the Langshan and Helanshan regions, we proposed that the northwest margin of the Ordos Basin was under the far-field effects of the collision of North China Plate and South China Plate in the Late Triassic, and the sinistral ductile strike-slip lead to the formation of regional pull-apart basin, accompanying the extension of lithosphere and the basaltic magmas eruption resulted from the decompression of asthenosphere.
1
Carboniferous–Middle Permian sedimentary- paleogeographic environment and source of the lithium-rich claystones in the Dianzhong Basin, SW China

ZhangJiahui, Yanzhen, XueChuandong, YuLiangjun, WeiAiying, FuChanglei, WangWei, WangYu, ZhouHonglin

Abstract: (25) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

The Carboniferous?Middle Permian sedimentary sequences are rich in bauxite, coal, calcite, limestone and other type ore deposits associated with numerous lithium-rich claystones in the Dianzhong Basin, SW China, and their metallogenic setting is constrained by spatial?temporal evolution of the sedimentary environments and relevant paleogeography. Systematical field investigation demonstrates that the Carboniferous sedimentation in the Dianzhong Basin is mainly dominated by terrigenous clastic and carbonate rocks of a littoral tidal flat-lagoon environment, and the Lower?Middle Permian sedimentary rocks mainly deposited in a lagoon-tidal flat-open platform environment. The Lower Carboniferous Datang Formation of which is mainly composed of carbonates with muddy shale interlayers of the tidal flat environment, and the lagoon deposition only occurs adjacent to the Niushoushan Paleo-high. The Middle Carboniferous Weining Formation and Maping Formation are littoral-tidal flat deposits, which are sporadically exposed around this uplift. The Lower Permian Daoshitou Formation is a suite of fine?grained terrigenous clastic rocks, with minor limestone lenses locally. The bauxite, coal ore deposits and lithium-rich claystones hosted in the Daoshitou Formation precipitated in a tidal flat?lagoon environment. The Middle Permian Qixia and Maokou formations consist of algal clastic limestone, dolomitic leucoblastic bioclastic limestone and medium- to coarse-grained dolomite, which deposited in an open-platform environment. Spatially, the thickness of the Datang and Daoshitou formations vary greatly in transversal, showing a thinning-southward trendency. The number of coal and bauxite layers also decreases to the southward. These characteristics demonstrate that the depth of seawater is shallowing to the south and the relevant deposits are close to their source area gradually. The Qixia and Maokou formations are widely exposed to the north and the corresponding thickness increases northward. This is consistent with the SE-high and NW-low paleogeography of the Dianzhong Basin indicated by paleocurrent data during the Early?Middle Permian, which also demonstrates that the Niushoushan Paleo-high is the major source region of the Daoshitou Formation. Geochemical data demonstrate that the Daoshitou Formation is rich in the aluminum- and lithium-rich claystones, and the contents of lithium and bauxite ores (Al2O3) are controlled by weathering of their source areas, and sedimentary conditions. When the contents of Al2O3 are less than 55%, and the ratios of Al2O3/SiO2 are less than 3, the contents of lithium are positively correlated with the contents of Al2O3, and of negatively correlations for other variation intervals. Regional geological data analysis demonstrates that the Niushoushan Paleo-high mainly comprises of the Precambrian intermediate-mafic volcanic and sedimentary rocks, which also occurred in a warm and humid environment during the Early?Middle Permian. This Paleo-high experienced regional uplifting and erosion because of continuous opening of the Paleo-Tethys during the Early Carboniferous to Middle Permian times, which also results in that the Precambrian volcanic rocks and relevant sedimentary rocks were eroded, and the volcanism was widespread. These eroded detritus and volcanic eruptions adjacent to the Niushoushan Paleo-high are the important source for the formation of the bauxite ore deposits and lithium-rich claystones in the Dianzhong Basin.
1
Characteristics of trace element geochemistry and the geological significance of fluorites from the Haidewula uranium deposit in Qinghai

Wu Jia, Liu Xiaodong, Wang Kaixing, Dai Jiawen, Yu Chida, Sun Liqiang, Zhu Kunhe, Yang Jianjun

Abstract: (25) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

The Haidewula uranium deposit is the first typical volcanic-related hydrothermal uranium deposit to be discovered in northwest China currently. Revealing the nature of the ore-forming fluids and the mineralized mechanism is favorable to understand the genesis of the deposit and to guide the prospecting in this area. Detailed studies on mineralogy, petrography and trace elements of fluorites from the deposit have been conducted in this paper. The results show that two stages of hydrothermal fluorite including metallogenic stage dark purple fluorite and post metallogenic stage purple fluorite have been identified, with the metallogenic stage dark purple fluorite closely associated with the uranium mineralization. The characteristics of trace elements and the REEs pattern are significantly different in two stage fluorites. The dark purple fluorite in the metallogenic stage is relatively enriched in Sr and Ba, while the purple fluorite in the post metallogenic stage is relatively enriched in REE and trace elements such as Co, Ni, Cu, Zn, Ga, Rb, Y, Zr, Nb, Mo, Cs, Pb, Th and U. The ΣREE of dark purple fluorite in the metallogenic stage ranges from 59.98×10-6 to 118.31×10-6, with a median value of 75.02×10-6, and the REE pattern is characterized by enriched LREE (LREE/HREE ratios median 5.06) and a strong fractionation between LREE and HREE ((La/Yb) N value median 12.24)), with moderate negative Eu anomaly (with median of 0.56), week Ce anomaly (with median of 0.99) and positive Y anomaly (with median of 2.21). The ΣREE of purple fluorite in the post metallogenic stage ranges from 194.12×10-6 to 207.67×10-6, with a median value of 195.55×10-6. The REE patterns of purple ?uorite is characterized by enriched LREE (LREE/HREE ratios median 4.76) and a relatively strong fractionation between LREE and HREE ((La/Yb) N value median 6.37)), with a well-pronounced negative Eu anomaly (with median of 0.09), positive Ce anomaly (with median of 1.33) and positive Y anomaly (with median of 1.90). Based on the comparison with the geochemical characteristics of the surrounding rocks and the pitchblende, two stages of fluorite (metallogenic stage dark purple fluorite and post metallogenic stage purple fluorite) in Haidewula uranium deposit were formed in the fluids with different sources. The metallogenic stage dark purple fluorite was formed in the acidic ore-forming ?uid rich in F- and Cl-, and maybe precipitated by the mixing mechanism of meteoric water with magmatic water in a reducing environment. The trace element geochemical characteristics of post metallogenic stage purple fluorite, such as with Ce positive anomaly and inheriting the Eu negative anomaly of the ore-bearing volcanic host rocks, indicated that the fluorite was formed in the oxidizing environment with higher proportion of meteoric water and higher oxygen fugacity and pH value in the fluid.
1
Geochemical characteristics and tectonic significance of podiform chromite in the Dongqiao in the middle part of the Bangong -Nujiang suture zone, Tibet

Zhangboyang, Xiongfahui, Xuxiangzhen, Qiutian, Zhangchengjie, Helanfang, Wangtianze, Yangjingsui

Abstract: (31) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

The Dongqiao ophiolite, located in the northern part of the middle part of Bangong -Nujiang suture zone, is composed of mantle peridotite and chromitite, and the mantle peridotite is manily harzburgite and dunite. Chromite is mostly lenticular and banded, and often with dunite cladding, both of which occur in the harzburgite dyke. The olivine Fo values (91.2~92.9) and Cr# values (70.16~76.60) of the para-mineral chromium spinel in the mantle peridote of Dongqiao are high, which are similar to Dingqing, Qielihu and Yilashan rocks in the Banong-Nujiang suture zone, indicating that the Dongqiao ophiolite has experienced a high degree of partial melting. The chemical composition of chromium-spinel of Dongqiao chromitite indicates that there are both high chromium-type chromitite (Cr# value is 60.67~82.67, Mg# value is 54.45~68.08) and high aluminum-type chromitite (Cr# value is 56.36~59.62, Mg# value is 67.20~72.68) in the ophiolite. The REE characteristics of the mantle peridote in Dongqiao show that it has the characteristics of pre-arc mantle peridote, and the trace element partitioning pattern is very similar to that of Izu-Bonin-Mariana, indicating that the Dongqiao ophiolite may have formed in the ocean floor spreading environment of plate subduction zone. The PGE element partitioning pattern of chromite is similar to that of Lobusa chromitite, which is characterized by enrichment of IPGE and loss of PPGE. The analysis of Dongqiao mantle peridotite and its chromite equilibrium melt shows that high-chromium type chromitite was formed in SSZ type forearc basin, high-aluminum type chromitite was formed in MORB type environment, and the adjacent ophiolite of Bangong -Nujiang suture zone indicates that Dongqiao mantle peridotite and its chromitite have undergone MOR→SSZ multi-stage evolution process. In the transition zone from dunite cladding to banded disseminated chromitite, Cr# value increases (67.22~68.48) and Mg# value decreases (57.35~74.56), which reflects the existence of different degrees of partial melting in the mantle source region. It is further indicated that the mantle peridotite and its chromitite may have undergone melt-rock reaction to a certain extent.
1
The multi-level structure and formation mechanism of the Kenya Rift Valley, East Africa

Jia Zhijie, Lu Quanzhong, Huang Weiliang, Zhuang JIanqi, Zhu Xinghua, Ma Penghui, Wang Feiyong, Wang Zuopeng, LIU YANG, He Ming, Zhao Junyan, He Zhiyuan, Huo Bingyao, Peng Jianbing

Abstract: (23) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

The East African Rift System, as the most famous continental rift and fault zone on earth, conducting research on the formation of ground fissures within the rift valley is of great significance for understanding the active rift process and guiding the engineering construction of the rift valley area. On the basis of field investigation, trenching, geophysical exploration, and helium isotope detection of ground fissures in the Kenya Rift Valley, East Africa, this article establishes a multi-level structure of ground fissures in the crust and analyzes their formation mechanisms. The results indicate that there are a total of 22 large ground fissures developed in the study area, mainly distributed in the rift basin between the eastern boundary fault and two volcanoes in the study area. Ground fissures appear on the surface as ruptures and collapses of loose sediments, and as simple tensile fractures with degassing on the surface of pyroclastic rocks. Resistivity detection shows that ground fissures are extensions of rock fissures in the crust. Based on the characteristics of helium isotopes, a multi-level structure consisting of ground fissures, rock fractures, faults, magma chambers, faults, and upper mantle has been revealed. On the basis of the above research, combined with the characteristics of crustal deformation and numerical simulation, the formation mechanism of ground fissures in Kenya Rift Valley, was revealed and summarized as follows: mantle upwelling-mantle intrusion-magma chamber expansion-surface fracturing.
1
Iron isotopic characteristics constraints and indicative significance of the Xiaohongshilazi Pb-Zn (Ag) deposit in Jilin Province

Wang Gaotian, Wang Da, Bai Feng, Xu Debing, Wang Guilong

Abstract: (35) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

The Xiaohongshilazi Pb-Zn (Ag) deposit is a representative medium-sized deposit within the Jizhong-Yanbian copper-nickel polymetallic metallogenic belt, the main views for deposit types mainly include VMS type, medium-low temperature hydrothermal vein type, and exhalative deposits overprinted by hydrothermal fluid. In order to constrain the ore genesis, the Fe isotope characteristics of pyrite and pyrrhotite are systematically investigated. The overall δ56Fe values range from –0.82‰ to 1.00‰; Compared with other various type deposits, we have found that the Xiaohongshilazi Pb-Zn (Ag) deposit shows the characteristics of both hydrothermal and sedimentary deposits, hence the metallogenic hydrothermal fluid should be hot spring, and MVT type is most suitable. The δ56Fe values of pyrite gradually decrease from stage 1 (1.00‰) through stage 2 (0.21‰ ~ 0.83‰) to stage 3 (0.08‰ ~ 0.12‰); in comparison, the δ56Fe values of pyrrhotite gradually increase from stage 1 (–0.82‰) through stage 2 (–0.55‰ ~ 0.13‰) to stage 3 (–0.23‰ ~ –0.21‰), which is the typical Rayleigh fractionation characteristics. Within coexisting mineral pairs, the pyrrhotite is preferentially enriched in light Fe isotopes relative to pyrite, which is the same with previous studies. In addition, a Fe isotope fractionation model has also been established, which imply that the collected samples were correspond to the intermediate period (33.96% ~ 63.70%) of the whole mineralization process, while 63.59% of the metal resources related to the early period (0.00% ~ 33.96%) and late period (63.70%~ 100.00%) have not been discovered. In summary, the Fe isotopic compositions is mainly controlled by Rayleigh process, although the Fe isotopic evidence supported the MVT genesis, the geological characteristics are slightly different hence it should be classified as an MVT-like deposit; and there is still further prospecting potential within orefield.
1
Growth model and geological significance of bedding-parallel fracture veins in Southeast Sichuan Basin1 Engineering Technology Research Institute, PetroChina Southwest Oil Gasfield Company, Chengdu, Sichuan 610017, China

Tianhe, Liyuegang, Zeng lianbo, Chenliqing, Wuqiuzi, YInyingzi, Lihong, Xuliang, Liyanyou, Yangxue, Lidu, Chenyao

Abstract: (11) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

Bedding-parallel fractures are widely developed in organic-rich shale, which are important reservoir space and lateral migration channel of shale gas, affecting the migration, enrichment, preservation of shale gas and the fracturing effect of reservoir. However, the formation of bedding-parallel fractures usually has multiple stages and causes, making the formation mechanism of bedding-parallel fracutures very complex and difficult to distinguish. This study takes the shale from the Wufeng-Longmaxi Formation in the Southeastern Sichuan Basin as an example. Based on field, core, thin section, and scanning electron microscopy data, the macroscopic characteristics of bedding-parallel fractures and the microstructure characteristics of filling veins were studied, and the formation mechanism of bedding-parallel fractures was analyzed. The results show that the surface of the unfilled bedding fractures is smooth and has obvious mirror features. The scratches and steps on the fracture surface can indicate the relative displacement direction of the surrounding rock on both sides of the fracture, and the fracture can extend several meters to tens of meters forward along the bedding plane. The bedding-parallel fractures are mostly filled with striped calcite and quartz minerals, with a width of 0.5cm~5cm. Bedding-parallel fractures contain three important microstructures, namely crack-seal bands, inclusion trails, and elongate crystals. The shape of the crack-seal band is controlled by the initial fracture, and the number of bands can indicate the times of fracture opening. The inclusion trails are parallel to the opening direction of the fracture and can track the opening trajectory of fracture. According to the different driving forces of fracture opening during the formation of veins, bedding-parallel fractures veins can be divided into three types: fluid overpressure type, tectonic compression type, and tectonic-fluid overpressure type. During the growth of bedding fractures and veins, they can serve as lateral migration channels for shale gas, affecting the enrichment and preservation of shale gas. And as mechanical weak surfaces, they have a significant impact on the hydraulic fracturing effect.
1
Structural Generation and Its Application in Ore-prospecting

Chen Bailin

Abstract: (11) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

Tectonic generation is an important concept of geomechanics and tectonic geology. Tectonic generation refers to the sequence in which structural planes with different mechanical properties and different orientations are formed in the same crustal movement under the continuous action of the same period and the same dynamic action mode, or because of the local change of boundary conditions, the structural features are controlled in turn. Structural generation emphasizes the genetic relationship between structural features and is the basis for determining structural types and establishing structural systems. The structural generation relationship is very common, which is different from the structural level. Different generation structures have the characteristics of time difference, derivation, absoluteness and invisibility. Low-order structures are often distributed within the influence range of higher-order structures and controlled by local stress fields. The study of ore-controlling structures should be from low order to high order. Starting with ore-bearing structure investigation, analyzing the mechanical properties and combination laws, then, the ore-controlling structure types are determined, and the ore-controlling laws of structures are summarized. The ore-prospecting prediction should be from high order to low order. According to the ore-controlling type of structure and the control law of structure generation, the possible position and direction of low-order ore-bearing structures are analyzed and the ore-prospecting prediction is carried out. Through the structure generation analysis of ore-controlling structures, it is considered that the Zoujiashan uranium deposit is not controlled by the NE-trending Zoujiashan-Shidong fault, but by the NEE-trending hidden structural belt with medium-low dip angle dipping to NNW, and the prospecting direction is along the SWW direction of the existing ore belt and the deep part with medium dip. In the Changjiang uranium ore field, uranium mineralization is not controlled by Mianhuakeng fault and Youdong fault, but by NNW (near SN)-trending structural belt with steep dip angle. The shallow secondary fault is ore-bearing (or ore-storing) structure, and the main structural belt merged from them and extended to the deep plays the role of guiding mineralization and transporting ore-forming hydrothermal solution (distributing of deposits). The ore-prospecting direction is the extension and deepening part along the NNW (near SN) –trending ore-bearing structure and the deep part of the surface mineral-free zone. When analyzing the structural generation, we should pay special attention to the genetic relationship of structural features, and also pay attention to structural periods. We should distinguish the structures before mineralization, during mineralization and after mineralization. Within a specific ore field, deposit or mineralization zone, we should objectively analyze the relationship between ore-guiding structures, ore-transporting (ore-matching) structures and ore-storing (ore-bearing) structures (that is, the relationship between ore-controlling structures and ore-bearing structures), then determining an ore-controlling structural type, constructing a structural ore-controlling model, and finally guiding the practice of ore-prospecting and prediction.
1
Study on the process of iron-aluminum differentiation in bauxite formation: a case study of the iron-aluminum rock series in the Jiujialu Formation of the Carboniferous System in Central Guizhou

Yang Ruidong, MO Hongcheng, LUO Chaokun, GAO Junbo, NI Xinran, Peng Rou, GAO Chuanqian, CHEN Jun, CHEN Jiyan

Abstract: (15) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

Based on the study of the iron-aluminum rock series of the Jiujialu Formation in the Carboniferous System of Central Guizhou, as well as the sedimentary sequence, sedimentary structures, and geochemical analysis, it is concluded that iron-aluminum differentiation primarily occurred during the depositional period. The banded, clastic, and oolitic structures observed in the ferruginous rock indicate its depositional origin rather than post-depositional iron migration. Geochemical characteristics show distinct elemental compositions between the ferruginous rock and bauxite, suggesting differences in sediment sources and depositional environments during the depositional period. The proximity of high-iron bauxite deposits to source areas and the distance of low-iron bauxite deposits from source areas further support the conclusion that iron-aluminum differentiation primarily occurred during deposition. The iron-aluminum differentiation in the Jiujialu Formation is closely related to global paleoclimatic changes, particularly the transition from a hot and arid climate to a cold climate during the early Viséan period. The abrupt intensification of rainfall led to the leaching of iron-rich material from the weathered crust, which was transported in colloidal form and deposited in lakes and swamps, forming ferruginous rock. Subsequent heavy rainfall events resulted in flood events, during which aluminum-rich weathered crust was transported as debris flows into lakes or swamps, leading to the deposition of clastic bauxite as a product of these flood events.
1
Fission track evidence of Cenozoic uplift and exhumation of Huayangchuan uranium polymetallic deposit in Xiaoqinling

Chen ZhiBai, Yan Jie, Sun Yue, Kang Qingqing, Pan Chunrong, Xia Fei, Pan Jiayong

Abstract: (13) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

The Huayangchuan uranium polymetallic deposit is a comprehensive super-large deposit dominated by U-Nb-Pb and associated with rare earth elements. In order to clarify the exhumation history of the deposit and the preservation of the ore body, this paper systematically collected 10 gneiss samples in Huayangchuan mining area according to the distribution characteristics of the ore body, and carried out apatite fission track test. The results show that the age of the samples is between 52.0 ± 2.9 ~ 35.2 ± 0.77 Ma, and the average track length is between 11.53~13.73μm. The thermal history simulation shows that the Huayangchuan area has experienced two stages of rapid uplift and denudation since the Cenozoic : ① Eocene ( 54 ~ 34 Ma ) and ③ Middle Miocene to present ( 13 ~ 0 Ma ), and ②Oligocene to Middle Miocene ( 34 ~ 13 Ma ). Combined with the regional tectonic evolution, the Cenozoic tectonic evolution model of Huayangchuan area is constructed. It is considered that the rapid uplift and denudation in the Eocene period is affected by the thrusting of Xiaohe fault from south to north and the extension of Huashan piedmont fault. During the period of 34 ~ 13 Ma, the study area was in the tectonic quiet period as a whole. The rapid uplift and exhumation since 13 Ma was mainly affected by the Huashan piedmont fault, resulting in the tilt of the study area from north to south. Fission track data and thermal history simulation show that the ore bodies on the southeast side of the study area are well preserved and have great prospecting potential.
1
Deformation and element redistribution characteristic of in-situ apatite in metamorphic rocks: a case study of metamorphic rocks in the Eastern Himalayan Syntaxis

ZHANG YanYan, ZHAO ZhongBao, DU JinXue, LIANG FengHua, MAO XiaoHong, TIAN ZuoLin, Ma XuXuan

Abstract: (38) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

The metamorphism and deformation of rocks can be well recorded by the structures and element distribution of accessory minerals. Especially, the metamorphic/deformation history can be revealed and analysized by in-situ chronologic dating. Apatite is a common accessory mineral in metamorphic rocks. With the rapid development of in-situ dating technology of apatite, it has become an important dating mineral in magmatic rocks and mineral deposit studies. In different metamorphic-deformation processes, a series of important problems about the deformation mechanism and behavior of apatite and its restriction effect on the element diffusion process have not been solved. In this study, rocks in the Eastern Himalayan syntaxis, which has the strongest tectonic deformation and metamorphism, are selected for research. SEM and CL observations show that the apatite in granulite does not show obvious compositional structure, while the apatite in mylonite shows obvious changes in light and dark, that is, composition changes. By statistical analysis of apatite distribution characteristics in thin sections, we found that the long axis direction of apatite in the two metamorphic rocks is approximately parallel to the main foliation. EBSD fabric analysis shows that the apatite in granulite shows obvious intra-granular deformation, while the apatite in mylonite shows almost no intra-granular deformation. The results of EPMA scanning of apatite composition show that the distribution of major elements of apatite in granulite is relatively uniform, while the distribution of Si elements of apatite in mylonite is obviously zonal or uneven, which is consistent with the results of CL scanning. Based on the above apatite deformation and element distribution characteristics, it can be preliminarily concluded that: (1) Although apatite in granulite is directionally distributed parallel to main foliation and occurred intra-granular deformation, it may be due to relative higher metamorphic temperature, which promotes the rapid diffusion of elements and makes the redistribution of elements tend to be uniform. Moreover, the late fluid action occurs element metasomatism along the low-angle grain boundary or near the fracture which are always perpendicular to the maximum tensile stress. (2) The apatite in mylonite is arranged parallel to the mylonite foliation, but almost no intra-granular deformation occurs, possibly due to the low deformation temperature (< 450o), or because the strain of mylonite is mainly concentrated in the quartz and mica domains, while the relatively tough apatite does not participate in deformation. The composition changes shown in the CL image and some major elements distribution maps may be indicating that the low metamorphic/deformation temperature have not led to the rapid diffusion of elements in apatite. (3) The preliminary age results show that the apatite in the granulite records multiple ages, indicating that the inherited apatite occurs in the element redistribution during metamorphism and late stage metasomatize of the apatite which has influence mineral isotope system, while the apatite in the felsic mylonite is the result of continuous fluid activity during the mylonitization process resulting in continuous crystallization of apatite. New results provide important information for the interpretation of apatite age in metamorphic and deformation rocks.
1
Biotite in highly evolved granite from the Zengjialong Sn ore deposit, China: Insights into magma source and evolution

Sun Keke, Chen Wei

Abstract: (18) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

Tin is an important strategic key metal and the study of its mineralization laws has valuable theoretical significance and economic value. Primary Sn mineralization is generally associated with highly evolved and relatively reduced granitic magmas. Compared with common granites, Sn-rich highly evolved granites often undergo complex evolution processes. We can’t obtain the early-stage magmatic compositions based on whole rock geochemistry analyses, which only represent the information of the last evolved samples, hindering our understanding of magmatic source and their evolution details. In addition, the explains for the whole rock analyses are not unique. Minerals crystallized in magma such as quartz, biotite, apatite can record the dynamic composition changes and fine evolution processes of magma that are difficult to reflect in whole rock analyses, showing unique advantages in the study of petrogenesis of granite. In this paper, we present a comprehensive major and trace element (including halogen) dataset for biotites from highly evolved granites in the Zengjialong Sn ore deposit. Biotites in the Zengjialong granite have a magmatic origin. They are characterized by low Mg# (5.70―9.93, mean = 7.63), high A/CNK values (1.77―1.98, mean = 1.88), similar to biotite compositions in S-type granites worldwide, suggesting the parental magmas were of meta-sedimentary origin. Biotite trace elements show that as the K/Rb ratios decrease, the Rb, Cs, and Sn increase and Pb decrease, indicating that the magma has experienced crystal fractionation dominated by K-feldspar. Tin contents in biotite increase by 4 times due to progressive fractional crystallization, indicating the Sn riched in the residual magmas. Biotites have low IV(F), IV(F/Cl), log(fHF/fHCl) and high IV(Cl) values, along with the negative relationships between IV(Cl) and IV(F/Cl), log(fH2O/fHF) and log(fHF/fHCl), suggesting the Zengjialong magma is F-rich and Cl-depleted magma system and the biotite crystallization process is accompanied by continuous fluid exsolution. The biotites in Zengjialong granite contains almost no Fe3+. In the Fe3+—Fe2+—Mg triangle diagram, the biotites are located below the FMQ line, indicating a low oxygen fugacity. The biotites in the Zengjialong granite record that the magma has an enriched source, high degree of differentiation, low oxygen, and continuous fluid exsolution. These processes are conducive to the tin enrichment and mineralization. Our study shows that biotite geochemistry data can be used to distinguish different magmatic-hydrothermal mineralization (Cu, Mo, W, and Sn) systems.
1
Sedimentary characteristics and geochemical constraints of borate deposits in salt lakes on Qinghai-Tibetan Plateau

Xiang Honglu, Fan QIshun, Li Qingkuan, Chen Tianyuan, Yang Haotian

Abstract: (11) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

Boron is a strategic key non-metallic mineral in China, widely used in new energy, new materials, electronic information and other high-tech fields. The salt lake type borate deposits are mainly distributed on the Qinghai-Tibetan Plateau and the most important and promising boron resource type in China. Boron-rich salt lakes in the Qinghai-Tibetan Plateau show hydrochemical zones and differences of borate deposit types in different hydrochemical of salt lakes from south to north, but there is lack of comparative study of boron-rich salt lakes in different zones.This paper summarizes and compares the sedimentary characteristics of solid boron deposits and the differences of geochemical parameters of boron-rich brines in carbonate type (I region), sodium sulfate-magnesium sulfate subtype (II region) and magnesium sulfate-chloride type (III region) salt lakes on the Qinghai-Tibetan Plateau. The main conclusions are obtained as follows:① Borate minerals are mostly deposited directly on top of the clastic sediments, and present interactive multilayer deposition characteristics, indicating that the deposition of borate deposits requires brackish water recharge and hydrological environment changes, which accords with the theory of "Brine diluted into salt"；② The deposition of borax and ulexite is associated with a large number of mirabilite, and the deposition of pinnoite and Kurnakovite is accompanied by a large number of magnesium-bearing carbonate mineral (Hydromagnesite and dolomite), which indicates that the deposition of borax and ulexite requires the recharge of waters high in Na+, and that the deposition of pinnoite and Kurnakovite requires the recharge of waters high in Mg2+；③ The boron precipitation conditions of salt lakes inⅠ,Ⅱ, and Ⅲ zones are similar, as shown by the brine pH value of more than 8 and the B content of more than 400 mg/L; however, there are differences between different salt lakes in terms of TDS, Mg, and Na content；④ Combined with the chemical composition of borate deposits types mainly containing Na+ and Mg2+.The B×10-Na-Mg terminary equivalent diagram in zones Ⅰ, Ⅱ and Ⅲ shows that the equivalent of Na and B are in the range of 0.2-0.6 and 0.4-0.7, respectively, whereas there are some differences in the Mg equivalence values, with zones Ⅰ < 0.1, and zones Ⅱ and Ⅲ in the ranges of 0.1-0.4.
1
Summary of the exploration achievements and gold mineralization of Jiaodong Xiling super large gold deposit

jia

Abstract: (12) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

Jiaodong is the most important concentrated exploration area for gold deposits in China. During the 14th Five Year Plan period, Shandong gold geology and mineral exploration Co., Ltd. explored another super large gold deposit -- Xiling gold deposit between Sanshandao-Cangshang fault zone. Its accumulated detected gold resources reach 580t, with an average grade of 4.24 g/t, making it the largest single gold deposit discovered in China at present. It is located between the Sanshandao gold deposit and the northern sea area gold deposit. It is the deep extension and lateral part of the Sanshandao gold deposit in the northeast direction, and is connected to the northern sea area ore body in the deep. In fact, the three are actually the same ore body. Xiling gold ore body controls a maximum strike length of nearly 2000m and a maximum extension depth of 2057m; it is found that the ore body is in the form of "short handled axe" inclined to the Northeast in the horizontal direction, and has obvious echelon in the vertical distribution. The gold resources are mainly concentrated at the elevation of -1000 ~ -2200m; At the northeast end of the mining area, the ore body has extended to - 2600m, and continues to go deep. The thickness of the ore body becomes thinner, the grade is low, and the deep gold mineralization becomes weaker; The ore body extends from shallow to deep in multistage steps, which generally shows the characteristics of steep and gentle alternating echelon mineralization. Through the study of fluid inclusions in the deposit, it is found that the gold ore-forming fluid belongs to H2O-CO2-nacl fluid with medium temperature (199 ~ 347 ℃) and medium and low salinity (0.35 ~ 8.28 wt.%) rich in CO2, which is consistent with the large-scale gold ore-forming fluid in Jiaoxi North University, but slightly different in the process of gold deposit precipitation and migration. The precipitation mechanism of Xiling gold is mainly fluid immiscibility, and the temperature and salinity of the fluid in the main metallogenic period change most obviously, from the shallower part to the later stage of mineralization, The properties of ore-forming fluids tend to be more uniform. There is a certain coupling relationship between the emplacement of fluids and the spatial echelon mineralization. Gold mineralization is mainly concentrated in the second and third echelon spaces, corresponding to the middle and late stages of the mineralization stage. The study of S isotope shows that pyrite δ34S value has the trend of first increasing and then decreasing. The initial sulfur source of Xiling gold deposit may be closer to magmatic sulfur. In the process of mineralization, ore-forming materials and ore-forming fluids were mixed with other sources. The gold ore in the area has experienced strong assimilation, mixing and alteration metasomatism. The main element SiO2 is moderately acidic, with high Al2O3 and K2O and low Na2O、 TiO2、 MgO and CaO. It is peraluminous potassic basalt and high potassic calc-alkaline series granite. The ree distribution form is right-leaning type enriched in LREE, enriched in large ion lithophile elements (LILE) and depleted high field strength elements (HFSE), which has similar geochemical characteristics with island arc magmatites in extensional tectonic setting. Comprehensive studies have shown that,Xiling gold deposit belongs to altered rock type gold deposit formed by mesothermal magmatic hydrothermal filling metasomatism according to its genetic type. It was formed in the extensional tectonic background under the failure mechanism of North China Craton in the early Cretaceous. In the early Cretaceous, lithosphere thinning and asthenosphere upwelling caused large-scale magmatic activity. The coupling of structure, magma and fluid created large-scale gold mineralization in this area.
1
The deposit types, spatial distribution and development and utilization of gallium and germanium resources in China

Yu Jinjie, Chen Qishen, Bi Minfeng, Chen Shaocong, Chen Xiaodan, Znang Rui

Abstract: (40) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

Gallium and germanium as by product of other ore deposits are the dominant mineral resources in China. The types of gallium deposits are divided into gallium-bearing hydrothermal deposits, gallium-bearing bauxite deposits dominated by monohydrate bauxite ores and gallium-bearing coal deposits in China. The resources of the first two types of deposits are dominated and available. The types of germanium deposits in China are divided into germanium-bearing medium-low temperature lead-zinc deposit, germanium-bearing magmatic hydrothermal deposit, germanium-bearing sedimentary deposit, germanium-bearing organic rock deposit and germanium-bearing volcanic rock deposit. Among them, the resources of germanium-bearing medium-low temperature lead-zinc deposit and germanium-bearing organic rock deposit are dominant and available. The spatial distribution, development and utilization of gallium- and germanium-bearing ore deposits in China are mapped. There are 423 gallium-bearing orefields, in which 117 are fully utilized orefields, 112 are partly utilized orefields, 7 are closed and 187 are fully unutilized. There are 69 germanium-bearing orefields, in which 18 are fully utilized orefields, 12 are partly utilized orefields, 4 are closed and 35 are fully unutilized. In general, although gallium- and germanium-bearing de posits are widely distributed in China, they are mainly concentrated in a few metallogenic belts. Gallium-bearing ore deposits are divided into 22 metallogenic belts (regions), and germanium-bearing ore deposits are divided into 13 metallogenic belts (regions). China is the most significant producer and exporter of gallium and germanium in the world. The gallium and germanium industry is small. A large number of primary gallium and germanium products exported to western developed countries every year. But high-end gallium and germanium products are basically dependent on imports in China.
1
The volcanic-intrusive rock sequences and metal mineralizations in rifted basin in the eastern Yunnan Province, China

FANG Weixuan, LI Tiancheng, GUO Yuqian

Abstract: (2) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

Alkali magmatism have special controlling on mineralizations in the metal ore-concentrated areas. However, obstacles have all the time placed on the deep exploration and mineral predication in the study area, for cognitive difficults exist on the volcanic-intrusive rock sequsences, metal mineralizations, and the magmatic superimposing intrusive tectonic system. Focused on the Dongchuan Fe-Cu-Au ore concentrated area (the Proterozoic marginal rifted basin) and the Gejiu Sn-Cu-W-Cs-Rb- polymetal ore-concentrated area (the Triassic arc-back rifted basin), the innovated mapping techniques of the tectonic lithofacies had been applied to dissect study on the volcanic-intrusive rock sequences related to the alkali magmatic activity, rifted basin evolution, rock associations, and magmatic superimposing intrusive system, in order to disclose the superimposing mineralizations of IOCG, Cu-Co-rutile deposits and Sn-Cu-W-Cs-Rb polymetallic deposits in the eastern Yunnan Province in China. This study suggests as the followings. First, the Neoarchean alkali rocks are composed of calcite albitite（2520±14 Ma）and Fe-rich alkalipicrite（2529±77Ma）in the Dongchuan Fe-Cu-Au ore-concentrated area. The Neoarchean-Paleoproterozoic Xiaoliukou Formation Complex（＞2.50Ga）and its top part, a special mapping unit with homotopy in different lithofacies（2.5 to 1.80 Ga）, are the new hosting strata of Cu-Co-rutile-REE mineralizations and had been reworked by the superimposed by the Mesoproterozoic volcanic-intrsuive rocks in the Dongchuan Fe-Cu-Au ore-concentrated area. Second, in the Mesoproterozoic the first member of the Yinmin Group, alkaline rocks, including rock assications of Fe-Na-rich alkali basic rocks, Fe-K-rich trachyte, and Fe-rich alkali diabase-gabbros, were formed at the Mesoproterozoic stage of volcanic rifting basin. Xikuangshan-type Fe-Cu deposits or IOCG deposits were hosted at the second to three members of the Mesoproterozoic Yinmin Group, Moreover, Fe-K-rich trachyte at the footwall of the Fe-Cu orebody hosted the monazite-type REE mineralization layer. IOCG system and rutile superimposing mineralization were formed in alkaline Ti-Fe-rich gabbros (1097 to1047Ma）, alkaline Ti-Fe-rich diorites, and alkaline monzoporphyry, all of these rock associations were formed during the Greenville Orogeny in eastern Yunnan. Third, the Triassic alkalipicrite and tephrite with primary enrichment of Sn-Cu-Zn-Li-Rb-Cs were produced at the of the Triassic arc-back rifted basin in the Gejiu area at the Eastern Yunnan Province in China. While they were superimposed by leucogranite, and they were responsibly for Sn-Cu-W-Cs-Rb-bearing phlogopite-type skarn. Final, alkali rocks with initial enrichment of metals or mineralization in the early stage of the rifted basin, were superimposed by alkaline intrusive rocks with metal mineralizations at the late stage, which may be main hypernormal mechanism for metal mineralizations the rifted basin at the Eastern Yunnan Province in China. Breccia-pipe of magmatic hydrothermal fluids in the alkaline magmatic superimposing intrusive tectonic system has evident controls on hypernormal enrichment of Cu-Co-rutile-REE superimposing mineralization, whereas leucogranite intruded the alkalipicrite and tephrite with Sn-Cu-W-Cs-Rb primary enrichment are responsibly for hypernormal enrichment of Sn-Cu-W-Cs-Rb-bearing phlogopite-type skarn.
1
Zircon U-Pb geochronology, petrogenesis and tectonic setting of granitic pegmatite in Guanpo area, the eastern part of the North Qinling Orogenic Belt

CHEN Guochao, ZHANG Xiaofei, PEI Xianzhi, LI Ruibao, LI Zuochen, WANG Shuo, CHEN Xiaozhen, WANG Yongqiang, Zhang Rongzhen

Abstract: (15) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

The granitic pegmatites of the North Qinling tectonic belt are important pegmatite areas in China. There are controversial about the formation age and petrogenesis of the granite pegmatite. This paper presents LA-ICP-MS zircon U-Pb age, Hf isotopic and geochemical data of the Xiahecun granitic pegmatites and the Shanghecun granitic pegmatites in the Guanpo area to determine the formation age, the magma source, the petrogenesis and tectonic setting. LA-ICP-MS zircon U-Pb dating suggests that the Xiahecun granitic pegmatites and the Shanghecun granitic pegmatites crystallized 360~361 Ma and 334.8 Ma, respectively. The Xiahecun granitic pegmatites and the Shanghecun granitic pegmatites contain garnet, muscovite and tourmaline, with high contents of SiO2, Na2O and K2O, and low contents of CaO, FeOt and MgO, and are mainly peraluminous. The Xiahecun granitic pegmatites and the Shanghecun granitic pegmatites show little fractionation between LREE and HREE, and have obvious positive Eu anomalies. The magma is enriched in large ion lithophile elements (LILE) such as Rb, Th, Ba and Cs, and depleted in high field strength elements (HFSE) such as Nb, Ta and Ti, with low Nb/Ta and Zr/Hf ratios, indicating a high degree of crystallization differentiation. The Xiahecun granitic pegmatite has low εHf values ranging from －11.7 to－6.2. Shanghecun granitic pegmatite εHf values rangs from －4.9 to 1.1, higher than that of Xiahecun granitic pegmatite. Based on this, the Xiahecun granitic pegmatite is the result of partial melting of the ancient crust, while the Shanghecun granitic pegmatite is the result of partial melting of the juvenile lower crust, and then magma assimilates and contaminate the wall rocks. The granitic pegmatite in the eastern part of North Qinling can be divided into northern rare metal granitic pegmatite and southern uranium granitic pegmatite.
1
Confirming and its structural significances of Middle Silurian Xinjie plagioclase amphibolite schist in the Longshan junction of the Qinling-Qilian orogenic belts

CHANG Yinglei, LUO Jinhai, CHEN Zhuo

Abstract: (10) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

The Qinling-Qilian Junction intersects at the Long Shan Tectonic Belt in the southwestern part of the North China Block, and the Longshan tectonic belt is the key area to reveal the spatio-temporal relationship between North China block, North Qinling orogenic belt and North Qilian orogenic belt. A set of Mesoproterozoic quartz diorite in Xinjie determined by predecessors has doubts in terms of rock type, formation age and formation environment. In this paper, petrology, geochemistry and U-Pb chronology of monazite and zircon have been studied for this set of rocks and biotite monzonite gneisses inclusions. This set of rocks has been renamed as Xinjie plagioclase amphibolite schist. According to geochemistry, the protolith is a set of basic magmatic rocks. Zircon U-Pb dating gives the formation age of protolith is 433.15 ±3.42Ma (Middle Silurian).Metamorphic zircon and monazite U-Pb dating gives metamorphic age of 427.9 ±1.46Ma. The protolith was metamorphic shortly after its formation. This is an important feature of Xinjie plagioclase amphibolite schist in the history of formation and evolution. Combined with the analysis of regional geological data, it is shown that in the late Ordovician-middle Silurian, Longshan area was in a strong back-arc extensional tectonic environment under the background of northward subduction in the eastern part of North Qilian. Large-scale basic-acid magmatic activity developed in Longshan area under this extensional background. The protolith of Xinjjie plagioclase amphibolite schist is the basic magmatic rock formed under this extensional background. The protolith experienced hydrothermal metasomatism associated with magmatism in the same period and became plagioclase amphibolite schist. The detrital zircon age of biotite monzonitic gneiss enclosed in plagioclase hornblende schist is in good agreement with the detrital zircon age of Huluhe Group(S₁H) in southern Longshan area, and its provenance area is closely related to Ordos block and North Qinling orogenic belt. The results of this paper show that the magmatism caused by back-arc extension in Longshan area during the late Ordovician to middle Silurian is large in scale and lasts for a long time, and there is a good time-space relationship between magmatism, metamorphism and sedimentation in this background.
1
Influence of multiple detachment layers on structural deformation of Dabashan foreland fold thrust belt--Based on discrete element numerical simulation

Zhang Xiaoyu, Li Jianghai, Dou Fangpeng, Xu Haixuan, Liu Chen

Abstract: (23) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

The Dabashan tectonic belt is a typical intracontinental orogenic belt in China, located at the transitional zone between the Qinling orogenic belt and the Sichuan Basin. It is the main distribution area for proven reserves of large and medium-sized oil and gas reservoirs in the Sichuan Basin. The study area has developed multiple sets of detachment layers, and the distribution of detachment layers controls the structural deformation. Previous studies have determined the main structural styles of the study area based on the geological outcrop data, 3D seismic data and other technical methods, but there is still a lack of quantitative analysis of the structural deformation process and Kinematics characteristics. This article uses the discrete element numerical simulation method to calculate the differences in structural styles displayed within the same time step using PFC2D software, and conducts discrete element single factor comparative simulation experiments to explore the differences in structural styles in multi detachment layer systems. The experimental results show that (1) The detachment layer plays a controlling role in the development of structures in the cross section. On the one hand, the number of faults in both the double detachment system and the multi detachment system is higher than that in the single detachment system. The introduction of detachment layers makes the structural development in the system more complex; On the other hand, from the analysis of the developed fault properties, it can be seen that as the number of detachment layers increases, the number of forward thrust faults in the system shows a gradual increase. The number of reverse thrust faults in the multi detachment layer system is less than the first two models, and is significantly less than the number of reverse thrust faults in the double detachment layer system. The middle detachment layer has an inhibitory effect on the formation of reverse thrust faults. (2) The introduction of detachment layers accelerates the vertical thrust velocity of faults, and the middle detachment layer plays a role in connecting the basement detachment layer and the upper detachment layer. The phenomenon of structural decoupling is common in the double detachment layer system, and the development of secondary faults and folds is the main feature in multi detachment layer systems. (3) The multi detachment system shows obvious characteristics of secondary folds and faults, which is more consistent with the profile of eastern Daba Mountains. The dual detachment system shows more structural decoupling characteristics, which is more consistent with the profile of western section.
1
Experimental progress and geological application of nitrogen and hydrogen impurities in diamond

Lu Zhiyun, Yang Jingsui, Lian Dongyang, Wu Weiwei, Yang Yu

Abstract: (10) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

The occurrence, content and distribution characteristics of nitrogen and hydrogen impurities, which are widely present in natural diamonds, are of great significance for understanding the material cycle and for estimating the residence time of diamond in the deep mantle. Since the first diamond crystal was produced by the high temperature and high pressure (HPHT) method, researchers have obtained a large amount of data on diamonds synthesized at different pressures, temperatures (P-T), and media components. This paper systematically summarizes the occurrences and contents of nitrogen and hydrogen impurities in diamond crystals synthesized in the metal-carbon, carbonate-carbon, carbonate-silicate-carbon, sulfide-carbon, nitride-carbon, and nitride-sulfide systems. In addition, the influence of [111] and [100] orientations on the nitrogen and hydrogen content in diamonds is analyzed from the perspective of diamond crystal structure. We also discuss the effects of P-T conditions, components on the existence forms of nitrogen and hydrogen impurities in synthetic diamonds. It is also reviewed that the aggregation of Ib→IaA, IaA→IaB nitrogen defect in diamond lattice follows a secondary kinetic process of conversion. Combining the typical forms and contents of nitrogen and hydrogen impurities in different types of natural diamonds, this article can provide further research directions for the formation environment of natural diamonds from the perspective of nitrogen and hydrogen impurities.
1
The characteristics and origin of the pre-Sinian rift in the Sichuan Basin

Tang Hao, Wu Guanghui, Zou Yu, Su Chen, Dai lan, zhang chen, Ma Bingshan

Abstract: (11) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

The Neoproterozoic supercontinent breakup is of significant role in the origin of the rift basin and its hydrocarbon on Earth. However, there is still debate on whether the superplume or subduction process has triggered the rift basin. The largest Sinian gasfiled in China has been found along the Deyang-Anyue rift in the Sichuan Basin. Owing to absence of geological data and low-resolution seismic data, it is an enigma on the origin and distribution of the pre-Sinian rifts in the ultra-deep subsurface. Together with seismic interpretation and compiled geochemical data, we discuss the characteristics and mechanism of the pre-Sinian rift in the Sichuan Basin. The results show that: (1) NE-trending Pre-Sinian rifts developed well with more than 5000 m thick deposits in the Sichuan Basin, which are different in rift architecture and distribution from the Sinian depression to show a Pre-Sinian tectonic discontinuity; (2) the ?Hf isotope values of the Neoproterozoic zircons show a distinct pattern from a decreased trend to an increased trend, and present a tectonic transition period at ca. 830~780 Ma; (3) the Pre-Sinian rifting initiated during the transition period was consistent subduction process rather than mantle plume process. In conclusion, the mid-Neoproterozoic transitional subduction has resulted in the distributed deep Pre-Sinian rifts in the Sichuan Basin, which is a new favorable hydrocarbon exploration frontier.
1
Relationship between deep density structure and seismic in Bomi area of Tibet

FAN Pengxiao, YU Changqing, WANG Ruixue, ZENG Xiangzhi, LI Weiqiang, ZHANG Yue

Abstract: (20) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

The Bomi region of Tibet is located in the northeast of the Namche Barwa tectonic junction.It is a key area for studying the evolution of tectonic junctions in the eastern Himalayas.At the same time,it holds great significance for the Sichuan-Tibet Railway project, which is a key transportation initiative during the Fourteenth Five-Year Plan period. Therefore, it is crucial to study the stability and safety of the region"s deep geological structure. However, the scarcity of geophysical data in the area, due to limitations in geological and geomorphological conditions, has resulted in limited research on the relationship between deep density structure and seismic in the Bomi region.This thesis obtains 1:200,000 bouguer gravity data in Bomi region for the first time.First,we used the wavelet transform multi-scale decomposition method, scratch analysis method and gravity 3D inversion method to divide the tectonic activity unit, we obtained the gravity anomalies of different , faults distribution and density structures. The analysis results show that the overall crust density in the Bomi region changes significantly, which is closely related to the fault distribution. At the same time, combined with the regional geological data,our inferred 20 faults in the Bomi area、found 4 large transverse density uneven zones and deduced the occurrence of Jiali fault zone which runs through the study area. In addition, using the seismic and aftershock activity records in the area, analyzing the relationship between deep density structure and earthquake. Finally, according to the transverse variation of fault structure density, seismic activty and gravity anomaly in the study area, it can be seen that the seismic, fault zone and rock density disturbance are closely related to the transverse unevenness, and the earthquakes are mainly located in the high-density area of the density difference zone. Based on the above analysis, We discussed the potential influence of deep density structure on major railway projects----Sichuan-Tibet Railway in Bomi area is discussed, and corresponding suggestions are put forward.
1
Electrical Structure of the Crust in the Jingerquan Region, Eastern Tianshan and Its Geological Implications

Hao Zejiang, Zhang Qiang, Gong Shengping, Zhao Keqiang, Li Yong, Lu Guifu, Su Wenli, Fu Yangang, Duan Zhuang, Gao Jianwong, Lin Lujun, Wang Zhenliang

Abstract: (26) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

To understand the electrical structure and geological structural characteristics of the Jingerquan region, eastern Tianshan, and to provide electrical evidence for its metallogenic mechanism, a magnetotelluric sounding profile was completed in the Jingerquan region, eastern Tianshan. A reliable electrical structure model was obtained by three-dimensional inversion. The results revealed that:(1)The shallow part of Kangur-Huangshan ductile shear zone has a high conductivity thin layer, under the strong ductile shear deformation, the shallow surface rock layer may be relatively broken and loose, thus endowed with fluids.(2)The Yamansu Fault provides a channel for fluid transport to depth, causing the fracture to exhibit high conductivity anomalies below it.(3)The mineralization model of the Hulu copper-nickel sulfide deposit is consistent with the magma channel mineralization model, where the Kangur Fault provides a channel for upward intrusion of the mantle-derived magma, and the magma carrying copper-nickel sulfides undergoes gravitational subsidence and aggregation mineralization at the channel turn, magma house or dilatation site; It is speculated that there may be basic rocks rich in sulfide at the depth of 2 km, suggesting that there may be Cu-Ni metallogenic potential in the depth.
1
Application of Compressed Sensing frequency lifting method in seismic data processing of well W1 in the Yingqiong Basin

LI Lei, WANG Xiangchun, LIU Mengling, LIAO Yi, ZHANG Guodong

Abstract: (8) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

In order to solve the problems of low resolution seismic data and complex sand body distribution and overlapping relationship in Yingqiong Basin, a complete data processing process including preprocessing, denoising, migration and bias post-processing is designed based on the original data of three years. In post processing, compressed sensing frequency lifting method was applied to pre-stack depth migration profile, and compared with blue filtering frequency lifting method and zero phase deconvolution frequency lifting method. The advantages of compressed sensing frequency lifting method were demonstrated, and the application of compressed sensing frequency lifting method to solve current geological problems proved its rationality in the subsequent development and implementation of the Yingqiong Basin. The results show that compared with the other two frequency lifting methods, compressed sensing frequency lifting method can protect the reliable low frequency information below the main frequency, expand the high frequency, and improve the data resolution. By comparing the waveform inversion results before and after compressed sensing frequency lifting, the superimposed characteristics of sand bodies can be revealed, and it is also helpful for the subsequent inversion work. As a new seismic data processing method, compressed sensing frequency lifting method can better solve the problems of low seismic data resolution, sand body distribution and complex overlapping relationship, and it is worth popularizing and applying in practical seismic data processing.
1
Late Quaternary segmentation activity of the southern part of the Karakorum fault and a study of the Chaxikang surface rupture

Hanshuai

Abstract: (20) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

Numerous large earthquakes have occurred in the Tibetan Plateau since the recent decades years, which has attracted widespread attention from scholars both domestically and internationally. However, there are some large-scale fault zones on the plateau, which not only have strong late Quaternary activity, but also have the tectonic conditions for generating strong earthquakes. The Karakorum fault is a large dextral strike-slip fault in the western part of the Tibetan Plateau, with the southern part of the Longmucuo Fault being the more active segment. The Perlan Ms 7.0 earthquake occurred in 1883 along this fault. It is helpful to understand the latest deformation behavior of the fault and analyze its seismogenic behavior by identifying the segmented activity characteristics of the fault and surface rupture. Based on high-resolution remote sensing image interpretation and field geological survey, the late Quaternary segmented activity of the southern section of the Karakorum fault and the Chaxikang surface rupture zone are studied in detail. The results show that the southern section of the fault can be divided into three primary segments: Ladakh-Chaxikang, Kunsha-Bar and Menshi-Gongzhu Co segment, which are respectively characterized by dextral strike-slip, dextral strike-slip tension and dextral strike-slip with with a horsetail normal fault. The minimum horizontal displacement measured at the surface rupture zone is 8-9m. Combined with the rupture length of ~200km, the magnitude of the earthquake is estimated to be ~7.5. The Karakorum fault zone, which regulates the material extrusion in the western plateau, gradually transforms from a rigid block migration mode in the northwest section to a more dispersed arc-shaped normal fault and strike slip deformation in the southeast section.
1
Jurassic anatexis and granite genesis in Amdo area,Northern Tibet

jianzhenzhu, pengyinbiao, jiangxingzhou, gaoxiangyu, jiwentao, lichuanzhi, yushengyao

Abstract: (16) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

The Ando microland massif in Tibet, as a microland massif within the Bangong Lake-Nujiang River suture zone, has recorded multiple phases of tectonothermal events since the Neoproterozoic-Mesozoic era, and is an ideal object for the study of the genesis of the deep-melt-granitoids. In order to reveal the characteristics of the fluid/melt activities during the subduction-folding process of the oceanic plate, a comprehensive study was carried out herein, combining the whole-rock geochemistry, systematic petrology, zircon internal structure, zircon U-Pb ages, and Lu-Hf isotopes. A comprehensive study was carried out. Petrographic observations show that the mixed gneiss retains key field macro- and microscopic evidence of deep melting: (1) light and dark bodies are interbedded in a laminated distribution, accompanied by weak fold deformation; (2) there are assemblages of fine grains at the boundaries of quartz and potash feldspar, and irregular crystallization of potash feldspars from edge to middle; (3) plagioclase feldspar and potash feldspar boundaries show highly acicular, elongate, or wedge-shaped quartz and feldspar grains, with "bead" structures along the quartz and feldspar grain boundaries. The cathodoluminescence images and zircon U-Pb dating results show that the zircons in the mixed-rock gneisses have a distinct core-rim structure, with a distinctive oscillatory ring in the zircon cores, which gives a magma crystallization age of ~510 Ma, and narrow metamorphic or deep-melting rims in the rims. The zircon in the light-colored body has obvious core-rim structure, and the CL image shows that the zircon core is highly luminous with oscillatory ring band, which may be inherited magmatic zircon, and the zircon rims show deep melting features such as weakly fractional bands of grayish to dark color or no fractional bands, and the age of the core is ~510-470 Ma representing the age of protolithic crystallization, and the rims have an age of ~184 Ma indicating the age of melt crystallization. The zircons of the granodiorite have typical magmatic zircon characteristics, with a magmatic crystallization age of ~180 Ma, which agrees with the age of the light-colored body within the error range. The εHf(184) values of deep-melting diagenetic zircons in the light-colored body range from -5.0 to -3.3, while those of granodiorite magmatic zircons range from -10.97 to -5.21. Whole-rock geochemical analyses indicate that Fe2O3T, MgO, TiO2, CaO, and REEs are almost completely retained in the dark-colored body, while a large number of LILEs (Rb, Sr, K, Ba ) are to the light-colored body. The light-colored body is divided into Type I light-colored body and Type II light-colored body according to the whole-rock REE characteristics and whether it carries residual hornblende, in which Type I light-colored body has higher total rare earth content and negative Eu anomaly, while Type II light-colored body has lower total rare earth content and positive Eu anomaly; the trend of the distribution of rare earths (REEs) of granodiorite eclogites is consistent with that of Type I light-colored with an enrichment of the large ionic proximate elements (Rb, Ba, and Th) and a Negative Eu anomalies; the synthesis of the existing regional data and the field relationship, microstructure, chronology and geochemical results obtained in this paper indicate that the black cloud plagioclase gneisses of the Ando microterrane occurred in the subduction and folding stage of the hydrous partial melting involving black mica, and that the type I light-colored bodies in the mixed rocks formed the contemporaneous granodiorite bodies through large-scale convergence, migratory evolution and encroachment.
1
Re-discussion on genetic type of the Daliang Uranium deposit at Motianling: evidence from elemental and isotopic compositions of pitchblende

Wangkaixing, Ye fancheng, Zhu kunhe, zhangjian, Liux iaodong, Tan shuang, Sun Liqiang, Yang Jianjun

Abstract: (24) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

The Daliang uranium deposit is located in the Motianling pluton, northern Guangxi Province. It represents the oldest uranium deposit that related to granitoid in South China. Recent studies indicate that the Daliang uranium deposit exhibits distinct characteristics from typical hydrothermal uranium deposits related to the Mesozoic granites in South China, suggesting the possibility of a different deposit genetic type. The elemental chemistry and isotopic compositions of pitchblende are favorable tools for determining the mineralization age and exploring the deposit genesis type. Therefore, based on previous research, this study conducts the chemical composition and isotopic dating of pitchblende to determine the mineralization age and genesis type of the Daliang uranium deposit. The research results demonstrate that the pitchblende in the Daliang deposit exhibits features such as insignificant fractionation between LREE and HREE with weak negative Eu anomaly, which are similar to typical pitchblende in synmetamorphic uranium deposits. Using EMPA U-Th-Pb chemical dating and LA-ICP-MS U-Pb isotopic dating, the mineralization ages of the Daliang uranium deposit are determined to be 378 Ma and 376±4 Ma (MSWD=0.62), respectively, coupled with regional ductile deformation events, indicating that the deposit formed during the Late Devonian and suggesting a connection to regional ductile deformation. Combining previous studies on the high salinity of the mineralizing fluids in the Daliang uranium deposit (average 19% NaCl equivalent) and the stable isotopic constraints on the fluid source, it can be inferred that the Daliang deposit is likely not a traditional hydrothermal vein-type uranium deposit associated with granite but should be classified as a synmetamorphic uranium deposit. During the process of forward shearing detachment at Motianling during the Devonian period, when the uplifted brittle-ductile shear zone formed in the middle to lower strata reaches shallow depths, the granitic mylonite enters the brittle-ductile deformation zone. The mineralizing fluids extract uranium from the granite and precipitate in the brittle-ductile deformation zone, forming the Daliang metasomatic uranium deposit. This study establishes, for the first time, the presence of synmetamorphic uranium deposits in granites of South China. This implies the potential involvement of different genetic models and processes in the hydrothermal uranium deposits of South China. This finding holds significant importance for future uranium exploration and research in South China and deserves attention.
1
Mineralization timing and characteristics of fluid of Na’e beryllium deposit in the Tengchong terrane

mingtianxue, He xiaohu, Tang Zhong, Chen Lei, Yang Qingbiao, Xue Ge, Wang Yunxiao, Su Xiaoyu

Abstract: (26) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

Beryllium (Be) is widely used in advanced science and technology and strategic emerging fields, and is an urgent strategic resource for our country. The Tengchong terrane, which has experienced a complex geological structural process, is an important part of the East Tethys Orogenic belt. In this terrane, frequently magmatic activities occurred during the Cretaceous-Cenozoic stage and a large number of tin (tungsten) -rare metal deposits (mineralizatioin) related to magmatism have been discovered. Geological survey and evaluation indicate that potential beryllium, rubidium, niobium, tantalum rare metal deposits may be formed in this area. The Na"e beryllium deposit is a typical granitic pegmatite type deposit discovered in the Tengchong terrane. The granitic pegmatite intruded into the wall rock of the early Cretaceous monzogranite. In this paper, we study zircon U-Pb chronology of granite pegmatite and monzogranite (the wall rocks) and fluid inclusion of beryl and quartz from the granite pegmatite to discuss the ore-forming age and physical and chemical conditions of the Na’e beryllium deposit. LA-ICP-MS zircon U-Pb dating yield ages of granitic pegmatite are 44.3 Ma~46.9 Ma, that of monzogranite is 122.9 Ma, indicating that the Na’e beryllium deposit was formed in Eocene and the wall rock of monzogranite was formed in Early Cretaceous. Thus, we suggest that they have no evolutionary relationship. Combined with the magmatic activities and tectonic evolutionary history of the Tengchong terrane, we suggest that the Na’e beryllium deposit may be the product of crustal material melting in a post collision tectonic setting caused by the convergence between India and Eurasia plates, and is a typical LCT pegmatite type beryllium deposit at a post orogenic stage. Beryl and quartz from the Na’e beryllium deposit have vapor-liquid two-phase NaCl-H₂O inclusions and a small amount of pure liquid phase water inclusions and CO₂ inclusions. The ore-forming fluid is characterized by medium-low temperature (172.0 _o^C~299.4 _o^C), low salinity (0.70%~3.87% NaCl eqv.), and low density (0.723 g/cm_-3^{~0.913 g/cm}_-3^).According to the estimation of pressure and depth for ore-forming fluid, the Na’e beryllium deposit was formed in a low-pressure shallow environment. The concentration center of lithium and beryllium in geochemical anomaly map is consistent with the tin mineralization and pegmatite belts, suggesting that the rare metal mineralization is closely related to tin mineralization and pegmatite belt in the Tengchong terrane. In combination with the discovery of niobium, tantalum, rubidium, lithium mineralization in this district, we suppose that there is a potential for rare metal mineralization in the Tengchong terrane.
1
Identification of the middle Neoproterozoic (750 ~ 740 Ma) bimodal volcanic rocks in the Western Dabie orogenic belt, central China: Constrains for the tectonic evolution of the Yangtze Block

XU Yang, JIN Xinbiao, DENG Xin, LIU Hao, ZhANG Weifeng, WANG Zhanling, YANG Zhenning, LI Ningning

Abstract: (15) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

It still remains controversial whether the Neoproterozoic tectonic setting of the northern margin of the Yangtze Block shifted from a compressional setting to an extensional setting at 820 ~ 800 Ma, or remained a subduction setting until ~ 700 Ma. Our new identification of the Taohua bimodal volcanic rocks in the Western Dabie orogenic belt provide new constraints on the Neoproterozoic tectonic evolution and dynamic mechanism of the Yangtze Block. The SIMS and LA-ICP-MS analysis on zircons from these bimodal volcanic rocks yield consistent U-Pb ages of 750 ~ 740 Ma. The basic volcanic rocks are tholeiitic, and exhibit N-MORB-like to arc-like trace element patterns, with variable whole-rock εNd(t) values (-0.05 ~ +5.96). These basic rocks were probably generated by decompression melting of a depleted asthenospheric mantle, and magma subsequently underwent fractional crystallization and wall-rock contamination. Among the acid volcanic rocks, rocks from the Xumengzhai area are enriched in silicon (SiO2≥75%), alkalis (K2O+Na2O≥7%), REE and HFSE (i.e., Zr、Hf、Nb、Y), with high Zr+Ce+Y+Nb (≥ 600×10-6) and 10000*Ga/Al ratios (≥ 2.6), showing a close affinity to fractionated A-type granites. Their evolved zircon εHf(t) (mostly of -12.32 to -1.88) and whole-rock εNd(t) (-13.29 ~ -9.60) values indicate an evolved crustal source region, which may be generated by partial melting of Early Neoproterozoic magmatic rock rocks in the region and the magma underwent fractional crystallization. Integrating the new data with previous results for Neoproterozoic rocks from the South Qinling-Tongbai-Dabie-Sulu orogenic belt, we propose that the 780~635 Ma bimodal magmas in this belt were probably formed in a continental rift environment with episodic extension-related asthenosphere upwelling and lithosphere thinning during the middle of Neoproterozoic. Melting of asthenosphere, lithospheric mantle and crust under high-temperature and low-pressure conditions, coupled with interactions between the asthenosphere and the lithosphere, played a prominent role in the formation of the 780 ~ 635 Ma bimodal-type volcanic rocks and diverse geochemical features in the magmatic counterparts.
1
Chemical characteristics of pyrochlore in carbonate of the Huayangchuan uranium-niobium deposit and its significance for mineralization

Huang Hui, Pan Jiayong, Wang Kaixing, Zhong Fujun, Wan Jianjun, Wu Bin, Yin Shuo, Yan Jie

Abstract: (10) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

Abstract: The Huayangchuan deposit in Shaanxi Province is located in the Xiaoqinling metallogenic belt in contact between the North China Craton and the Qinling orogenic belt. It is a world-class uranium and niobium polymetallic deposit related to carbonatite, in which pyrochlore is the major U and Nb-bearing mineral. Although the Huayangchuan metallogenic mechanism has been well studied, the magmatic-hydrothermal evolution process of the deposit and its relationship with mineralization were poorly understood. Hereby, this paper study mineralogy, chemical composition and evolution characteristics of two types of primary pyrochlore (pcl Ⅰ and pcl Ⅱ) and three types of altered pyrochlore (pcl Ⅰ alt1, pcl Ⅰ alt2 and pcl Ⅱ alt) in the Huayangchuan deposit. The results show uranium and niobium mineralization in Huayangchuan carbonatite is closely related to the Late Triassic magmatism. It was related to a mantle-derived, initially U-rich carbonatitic magma, which has been further enriched in U by crystallization differentiation and formed the primary (magmatic) pyrochlore (pcl I), primary pyrochlore (pcl Ⅱ) and primary uraninite (Ur1) through partial melting from the mantle. In the early Cretaceous, the carbonatite in Huayangchuan were subjected to high-temperature hydrothermal alteration, and part of Nb and U released from the early pyrochlore (pcl Ⅰ) were dissolved and reactivated by the high temperature high-F fluid, which formed the primary uranite (Ur2), the altered pyrochlore (pcl Ⅰ alt1) and the secondary titanite (Ttn2). The primary pyrochlore (pcl Ⅰ) and primary pyrochlore (pcl Ⅱ) can be replaced by the altered pyrochlore pcl Ⅰ alt2 and altered pyrochlore pcl Ⅱ alt in the post ore low-temperature alteration. These results indicate that two magmatic-hydrothermal uranium-niobium mineralization and one post-mineralization low-temperature hydrothermal alteration occurred in Huayangchuan deposit during late Triassic and early Cretaceous.
1
Spatial-temporal distribution, resource potential and exploration progress of carbonatite-type rare earth deposits in central and southern AfricaTANG Wenlong¹⁾^,2⁾

Tang Wenlong

Abstract: (37) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

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.
1
Characteristics of melt inclusions of Miocene adakitic porphyries in the southern margin of Lhasa terrane

Zhao Xiaoyan, Yang Zhusen, Dong Yanrui, Liu Chang

Abstract: (11) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

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.
1
Discrete Element Numerical Simulation of fault development characteristics of Strike—slip Pull—apart Basin

LI Xin, HUANG Lei

Abstract: (21) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

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.
1
Study on lithologic classification method based on lithologic index and 3D feature space

Zhang Qunjia, Wang Le, Liu Lei, Wang Yalei

Abstract: (20) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

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.
1
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

Abstract: (50) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

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.
1
The Effect of Enhanced Basalt Weathering on Soil Heavy Metals

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

Abstract: (96) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

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.
1
Deep explanation model of the VMS-type deposit in the Ashele ore district

Meng guixiang, Deng zhen

Abstract: (39) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

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.
1
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

Abstract: (61) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

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.
1
Discussion on S-Pb-H-O-He-Ar isotope composition and genesis of the Sanhetun gold deposit in Heilongjiang Province

liubaoshan

Abstract: (27) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

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.
1
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

Abstract: (71) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

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.
1
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

Abstract: (31) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

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).
1
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

Abstract: (67) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

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.
1
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

Abstract: (8) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

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.
1
Large-scale autogenic stratigraphic mechanisms and Autostratigraphy

WANG Junhui, MUTO Tetsuji, XIAN Benzhong

Abstract: (39) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

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.
1
Characteristics of mylonite magnetic fabrics and constraint on the relationship between the shear zone deformation and mineralization

likang, jiaoqianqian

Abstract: (34) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

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.
1
Late Quaternary activity and paleoearthquake recurrence characteristics of Litang Fault in Western Sichuan

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

Abstract: (17) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

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.
1
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

Abstract: (20) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

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.
1
Restudy on the Cranium of the Early Triassic Hupehsuchus nanchangensis ( Diapsida: Hupehsuchia)

Zhao Bi, Zou Yarui, Li Jiangli

Abstract: (80) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

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.
1
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

Abstract: (30) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

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.
1
The deposit types, spatial and temporal distribution and prospecting direction of rare earth deposits in China

Yu Jinjie, Chen Shaocong, Chen Xiaodan

Abstract: (74) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

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.
1
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)

Abstract: (31) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

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.
1
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

Abstract: (74) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

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.
1
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

Abstract: (20) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

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.
1
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

Abstract: (65) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

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.
1
Discovery and geological significance of andesite intercalation in the “Dibuco Formation” in Nixiong area, Central Tibet

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

Abstract: (16) HTML (0) PDF (0.00 ByteKB) (0)

Abstract:

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.
1

Select All

Display Method:: |

Home

About Journal

Editorial Board

Publication Ethics

Instruction

Subscription

Published

OA Statement

Contact us

中文

Volume 98,2024 Issue 4

Research Articles

Technical Method

Appendix

Volume 98,2024 Issue 4

Research Articles

Research Articles

Research Articles

Research Articles

Sweep code subscribe

User Login