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YANG Tao，LI Yanyu，YANG Shuang，WU Feixiang
2026,100(1):1-12, DOI: 10.1111/1755-6724.70024
Abstract:
The Series Barbini (subfamily Cyprininae sensu lato) is the most species-rich group within the family Cyprinidae, primarily confined to warm regions of southern Eurasia and Africa. The distribution patterns and evolutionary history of Chinese cyprinins have been effectively shaped by the Cenozoic uplift of the Qinghai–Tibet Plateau and the evolution of the Asian monsoon. Here, we describe two new fossil fishes from the early and middle Miocene of the Lunpola Basin in central Qinghai–Tibet Plateau, China, preserving the ethmoid and the rear of the occipital regions of the neurocranium, infraorbitals, hyopalatine arch, abdominal vertebrae, and some dorsal-fin pterygiophores and unbranched fin rays. Through detailed morphological comparisons, these fossils show definite affinities to Cyprinidae according to the morphology of the neurocranium, vertebral column, and dorsal fin rays; and one of which is classified into the Series Barbini, while the other can only be assigned to the Cyprinidae family level. These findings reveal that the hinterland of the plateau of the early Neogene should have hosted cyprinin fishes of greater diversity than today. This also indicates a warm-temperate paleoclimate suitable for their survival during that period, consistent with the paleoenvironmental and paleoclimatical conditions reconstructed from the contemporaneous mammalian fossil and palynological evidences.
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JIANG Zikun，TIAN Ning，HAO Ruiying，WANG Yongdong，NING Zhenguo，WU Hao，SUN Deyu，WANG Cai
2026,100(1):13-19, DOI: 10.1111/1755-6724.70034
Abstract:
The wood anatomy of corystosperms is fundamentally consistent with that of gymnosperms, yet their growth ring boundaries share anatomical features with extant angiosperms. This transitional morphology strongly supports the interpretation of corystosperms as an evolutionary intermediate between gymnosperms and angiosperms. The first application of X-Ray fluorescence (XRF) chemical analysis to fossil wood taxa of Fengweioxylon yielded the above conclusion. By using growth ring analysis and ecological reconstructions, we suggest that corystosperms were large evergreen trees with leaf retention periods of three to five years. They likely thrived in warm summer environments where prolonged foliage retention provided adaptive benefits.
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LIAO Cuijing，ZHANG Chaoyu，LI Suping，LIU Weiqing
2026,100(1):20-32, DOI: 10.1111/1755-6724.70035
Abstract:
Quantonenpollenites, a pollen taxon which was assumed to be angiosperm, is of great significance in confirming the geological age of its bearing strata. Aims to clarify the taxonomic affiliation of Quantonenpollenites, we investigated the external morphology and internal structure using Light Microscopy (LM), Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM). According to TEM observations, the exine of Quantonenpollenites pollen is unstratified with the absence of a columellar layer, and the exine is tightly connected with the intine. Based on comprehensive morphological evidence, especially the lack of columellar layer which is typical characteristics existing in almost all angiosperm pollen, the botanical affinity of Quantonenpollenites should be attributed to gymnosperms rather than angiosperms as previously thought. Through comparative analysis, it may have a close affinity with Ephedra, but further analytical data are still needed for verification. As a characteristic palynological type of the Quantou Formation in the Songliao Basin, the occurrence of Quantonenpollenites has indicative significance for determining the age of the hosting strata. By systematically clarifying the phylogenetic affiliation of Quantonenpollenites, together with the other associated palynomorphs, this study provides crucial reference materials for defining the stratigraphic age range of the Quantou Formation (Cenomanian to early Turonian), improves the resolution of stratigraphic age calibration of the Quantou Formation, and provides key paleontological evidence for the refined division of the terrestrial Cretaceous chronostratigraphic framework in the Songliao Basin.
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2026,100(1):33-53, DOI: 10.1111/1755-6724.70038
Abstract:
This study investigates the facies development and sedimentology of the Late Permian Chhidru Formation, a mixed carbonate-siliciclastic unit exposed in the Western Salt Range, Potwar Basin, Pakistan. The formation is subdivided into four lithological units reflecting lateral variability, with thicknesses and lithologies ranging from fossiliferous sandy limestone to interbedded limestone and sandstone. These successions record a depositional shift from a carbonate platform to mixed carbonate-clastic, and ultimately, clastic-dominated environments. Lithostratigraphy suggests deposition on the underlying Wargal Limestone carbonates during a Late Permian sea-level fall on the northwest Indian margin of Gondwana. Similar Permian successions with identical lithological characteristics are documented in the Persian Gulf (Dalan Formation), Arabian Platform (Khuff Formation), and Iran (Nesen and Hambust formations). Petrographic analysis reveals deposition in the distal middle to proximal inner shelf settings of a carbonate-siliciclastic mixed, unrimmed platform. Based on identified foraminiferal assemblages, the Chhidru Formation's age is estimated to range from the late Wuchiapingian to Changhsingian stages of the Lopingian epoch.
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ZHAO Mingsheng，TIAN Jingchun，SU Bingrui，ZHANG Xiang
2026,100(1):54-68, DOI: 10.1111/1755-6724.70037
Abstract:
The Ordos Basin is a large superimposed hydrocarbon-bearing basin in China, and further research on the sedimentary characteristics and sedimentary evolution of the sequence framework of target layers is of great theoretical and practical significance for guiding oil and gas exploration. The sedimentary facies and sedimentary evolution of the high-resolution sequence framework of the Carboniferous Taiyuan Formation in the Hangjinqi area have been systematically analyzed for the first time by drilling, logging and seismic data. The results show that four types of sequence interfaces can be identified in the Taiyuan Formation: regional unconformity surfaces, scour surfaces, lithologic–lithofacies transformation surfaces and flooding surfaces. According to the sedimentary response caused by the upward and downward movements of the base level at different levels, the Taiyuan Formation can be divided into 2 long-term cycles (LSC1–LSC2), 4 mid-term cycles (MSC1–MSC4) and 7 short-term cycles (SSC1–SSC7). The long- and mid-term cycles correspond to members T1 and T2 and layers T1-1, T1-2, T2-1, and T2-2, respectively. Long-term cycles are dominated by C1; mid-term cycles are dominated by C1 and C2, followed by A2; and short-term cycles are dominated by C1, C2, A1 and A2. Under the high-resolution sequence stratigraphic framework, the Hangjinqi area underwent a transformation of fan delta and tidal flat depositional systems during the Taiyuan Formation sedimentary period. In the MSC1–MSC2 stage, owing to a large-scale paleocontinent, the fan delta sedimentary body, which was limited in scale and scope, developed only in the southeastern corner and gradually transitioned basinward to tidal flat facies. In the MSC3–MSC4 stage, as the paleocontinent continuously decreased and the sedimentary range expanded, fan-delta plain sedimentation began in the study area. Several braided distributary channels with poor connectivity developed on the fan-delta plain, and between them were floodplains and peat swamps.
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CAO Yiwen，ZHOU Xiwen，DONG Jie，DENG Xuanyu
2026,100(1):69-81, DOI: 10.1111/1755-6724.70025
Abstract:
Debate has persisted over whether the metamorphic basement of the Zhoushan Islands, easternmost Cathaysia Block, is Precambrian. Here, representative metamorphic rocks from the Qushan Islands were investigated using petrography, mineral chemistry, phase equilibria modeling and SHRIMP zircon U-Pb dating to constrain their metamorphic evolution and tectonic significance. Both the pelitic granulites (garnet-kyanite-perthite -biotite-quartz) and the mafic granulites (garnet-clinopyroxene-amphibole-plagioclase-quartz) reached high-pressure granulite-facies conditions of 1.2–1.4 GPa/820–900°C, and recorded three metamorphic stages along a clockwise P-T path with post-peak isothermal decompression. This trajectory indicated rapid exhumation of thickened continental crust during collisional orogeny. Metamorphic ages of 254 ± 3 Ma, 262 ± 4 Ma and 259 ± 3 Ma were obtained for mafic granulite, pelitic granulite and marble, respectively, and were consistent with the emplacement age of 259 ± 4 Ma for a pegmatite vein. Detrital zircons in metasediments spanned 2706–330 Ma, which constrained the latest deposition to ~330 Ma; thus represented mid-Paleozoic sediment metamorphosed during the late Paleozoic rather than Precambrian basement. We conclude that the Indosinian tectonothermal event in the Cathaysia Block had originated from late Paleozoic–early Mesozoic collisional orogeny between the South China Plate to the north and the Indochina Block to the south.
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HU Yuhua，ZHAO Yan，LU Junsheng，GOU Longlong，.M. GEORGE，AO Wenhao，ZHANG Chengli，ZHAI Mingguo
2026,100(1):82-98, DOI: 10.1111/1755-6724.70016
Abstract:
This study provides new evidence for a significant Neoproterozoic tectono-thermal event in the southern Dharwar Craton, based on U-Pb dating of rutile and monazite from metamorphic rocks of the Sargur Group. Trace element analysis of rutile in garnet-bearing amphibolite, amphibolite, garnet-bearing staurolite-kyanite schist, and grunerite-garnet schist suggests that their protoliths were primarily basaltic rocks, sediments with mafic component, pelitic sediments, and mixed sediments with both mafic and felsic components, respectively. Rutile U-Pb ages of 625 ± 22 Ma (garnet-bearing amphibolite), 752 ± 5.1 Ma (amphibolite), 836 ± 4 Ma to 663 ± 26 Ma (garnet-bearing staurolite kyanite schist) and 860 ± 13 Ma (grunerite-garnet schist), along with a monazite U-Pb age of 789 ± 4.4 Ma (garnet-bearing staurolite kyanite schist), record a significant Neoproterozoic (860–625 Ma) tectono-thermal event along the southern margin of the western Dharwar Craton. This event is most likely associated with aborted rift-related alkaline magmatism along the northern margin of the Southern Granulite Terrane (SGT) and the southern margin of the Dharwar Craton. Given the lack of direct evidence for the assembly of the Rodinia supercontinent in the Dharwar Craton and SGT, this Neoproterozoic event is unlikely to be related to the breakup of Rodinia.
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Elwan I. WAHEED，Abdel-Karim M. ABDEL-AAL，Azer K. MOKHLES，Zamzam A. SARA，Shaimaa A. EL-SHAFEI
2026,100(1):99-120, DOI: 10.1111/1755-6724.70023
Abstract:
Homret Ghannam alkali feldspar granite (HGAFG) in the central Eastern Desert (CED) of Egypt represents a distinctive example of late Neoproterozoic magmatism in the Arabian-Nubian Shield (ANS). This study integrates field observations, petrography, mineral chemistry (EMPA), and whole-rock geochemistry to investigate its petrogenesis, geodynamic evolution, and rare-metal potential. HGAFG comprises two cogenetic varieties, alkali feldspar granite and riebeckite-bearing granite, hosting rare-metal minerals such as zircon, fluorite, columbite and apatite. HGAFG exhibits diagnostic A-type geochemical characteristics, including high SiO? contents (73.81–77.86 wt%), metaluminous to mildly peralkaline composition (ASI: 0.92?1.03), enrichment in HFSE (Zr ≈ 791.80 ppm, Nb ≈ 68.12 ppm, Y ≈ 90.81 ppm) and ΣREE (103.40?475.57 ppm), and pronounced negative Eu anomalies (Eu/Eu* = 0.07–0.20). Zircon saturation thermometry yields high crystallization temperatures (TZr ≈ 908.87°C) and low emplacement pressures (1.46 kbar) under reducing conditions (?O? ≈ ?11.5). The mineralogical and geochemical results reveal that HGAFG originated from a hybrid, fluorine-rich magma generated by anatexis of lower crust, followed by extensive fractional crystallization, during late post-collisional extension associated with lithospheric delamination. The reduced nature and fluorine enrichment of HGAFG magma promoted the mineralization of Nb–Ta–REE phases, highlighting its significance as a fertile, high-temperature product of the terminal magmatic stage in ANS evolution.
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LI Zhenglin，LIU Xijun，SONG Yujia，ZHAO Bing，LIU Lei，YU Hongxia，SHI Yu
2026,100(1):121-136, DOI: 10.1111/1755-6724.70020
Abstract:
High-Mg andesites (HMAs) typically originate in subduction-related tectonic settings, including active continental margins and island arcs, and studies of HMAs can constrain the tectonic evolution of the South China Block and Paleo-Tethyan Ocean. This paper presents new chronological and geochemical data for high-Mg gabbroic diorites in the Funing area, southern South China. The gabbroic diorites yield ages of 254–249 Ma, and have moderate SiO2 contents (51.3%–57.8%), high MgO contents (4.6%–10.2%) and Mg# values (52–75), enrichment in large-ion lithophile elements and light rare earth elements, and depletion in high-field-strength elements—collectively displaying geochemical signatures typical of sanukites. The gabbroic diorites have radiogenic initial Sr and Pb isotopic compositions, and negative εNd(t) and εHf(t) values. These characteristics distinguish the Funing gabbroic diorites from subduction-related igneous rocks in the Paleo-Pacific tectonic domain. Instead, they are isotopically similar to HMAs and basalts along the Paleo-Tethys suture. We propose the high-Mg gabbroic diorites and basaltic andesites in Funing area share a common mantle source, linked to subduction and rollback of the Paleo-Tethyan plate beneath the South China Block, which triggered back-arc rifting and partial melting of the metasomatized lithospheric mantle during the Late Permian to Early Triassic.
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ZHANG Hao，LI Peng，LI Jiankang，YUAN Lulu，JIANG Pengfei，LIU Ze，YIN Jin，CHEN Zhuo
2026,100(1):137-155, DOI: 10.1111/1755-6724.70008
Abstract:
Elucidating the mineralization mechanisms of individual granitic stages and tracing magmatic evolution processes are critical for establishing mineralization models of large-scale batholiths. The Mufushan granitoid batholith, renowned for multistage magmatism and large-scale rare metal mineralization, mainly comprises biotite, two-mica, and muscovite monzogranite. Existing research has predominantly focused on biotite and two-mica granite, whereas muscovite granite, as the most highly differentiated lithologic unit, remains understudied regarding its mineralization mechanisms and evolution characteristics. Focusing on two newly discovered Li-rich granites, namely tourmaline muscovite granite (TMG) from Shiniuchong and garnet muscovite granite (GMG) from Huanglongxiang, this study clarifies their intrusion ages, Li occurrence states and enrichment mechanisms, while establishing the magmatic evolutionary pathway. The results show that the U-Pb ages of columbite-tantalum and zircon are 130.2 ± 1.0?Ma (TMG) and 138.2 ± 1.0?Ma (GMG), respectively, confirming Early Cretaceous Li-rich magmatism. The Li concentrations in muscovite from the Li-rich muscovite granites are high (mean 3328?ppm), compared to those in Mufushan ordinary muscovite granites (<1500?ppm), but the dominant Li-bearing minerals are still classified as muscovite or phengite. Li enrichment of mica in this Li-rich granite system is controlled by the magmatic differentiation-dominated vector Si2LiAl-3, differing from that in cogenetic pegmatite systems, indicating distinct Li enrichment pathways between two mineralization processes and thereby endowing this system with the potential to evolve into granite-type Li deposits. Mica geochemistry and Rayleigh fractionation modeling indicate the Li-rich muscovite granites, along with biotite and two-mica granite in the Mufushan area, represent products of different stages of co-magmatic evolution. Crystal fractionation is the key mechanism controlling Li enrichment, requiring effective separation of at least 75% of the melt to drive preliminary Li enrichment in the highly differentiated granite. These findings significantly advance understanding of mineralization processes in large-scale batholiths, providing valuable insights for regional Li exploration.
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YIN Shuping，XIE Yuling，LI Xiaoyu，CHENG Long，ZHU Zhimin，DAI Zuowen
2026,100(1):156-168, DOI: 10.1111/1755-6724.70022
Abstract:
Strontianite-rich carbonatite, containing over 30 vol% carbonate minerals predominantly composed of strontianite (SrCO3), is identified in the Zhengjialiangzi ore segment of the Muluozhai rare earth element (REE) deposit, western Sichuan Province, China. It exhibits a unique mineral assemblage dominated by strontianite, fluorite, bastn?site, barite, calcite and dolomite, distinguishing it from conventional calcio-, magnesio-, ferro-, or natro-carbonatites. The rock shows extreme enrichment in REEs (ΣREE = 47335–64367 ppm), with strong LREE/HREE fractionation [(La/Yb)N = 1151–2119] and notably high concentrations of high-value critical REEs (e.g., Pr, Nd, Tb, Dy), 5–10 times greater than those in local calcite-dominated carbonatites. Trace element patterns indicate significant enrichment in REEs, Sr, and Ba, along with depletion in high-field-strength elements (HFSEs; e.g., Nb, Ta, Zr, Hf). In-situ Sr isotopes of strontianite [(87Sr/86Sr)i = 0.706190–0.707305] indicate an enriched mantle source (EMI–EMII). Sr enrichment is attributed to initial mantle source enrichment and extensive fractional crystallization, possibly accompanied by minor wall-rock assimilation. We propose that the strontianite-rich carbonatite formed from a highly evolved, Sr- and REEs-rich carbonatitic magma that intruded into shallow structural breccias, followed by rapid cooling. Its formation is associated with a continuous melt-fluid evolutionary process that is characteristic of carbonatitic systems.
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2026,100(1):169-187, DOI: 10.1111/1755-6724.70012
Abstract:
Epithermal deposits are characterized by complex low-temperature hydrothermal alterations, but the links between mineralization and superimposed alteration are obscure and require further elucidation. This study employs short-wave infrared (SWIR) spectral scalars for alteration mineral mapping and three-dimensional modeling of the Ulan Uzhur Ag polymetallic deposit, a newly discovered epithermal deposit in the Qimantagh. Alteration zoning transitions from illite-muscovite-carbonate-pyrite in the core (Zone I), through muscovite ± illite-kaolinite-chlorite-carbonate (Zone Ⅱ), to muscovite-chlorite-biotite (Zone Ⅲ) at the periphery. The Zone I with mineralization features long-wavelength white mica (wAlOH > 2207 nm) with a high Illite Crystallinity (IC) (mean > 2.0), suggesting a relatively high-temperature environment conducive to mineralization. Petrographic analyses with fluid inclusion and IC curve characteristics suggests that fluid boiling may be a pivotal mechanism for mineral precipitation. Furthermore, surface mapping and deep three-dimensional modeling of spectral characteristics reveal a correlation between long-wavelength white mica, high IC and mineralization zones. These findings indicate that SWIR spectroscopy reveal the evolution of fluids and provide valuable guidance for future exploration efforts.
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WU Xiaoqi，WANG Ping，LIU Quanyou，NI Chunhua，ZHANG Yi，ZHU Dongya，JIA Huichong，XIANG Liange
2026,100(1):188-199, DOI: 10.1111/1755-6724.70030
Abstract:
The Ordovician Majiagou Formation (O1m) in the Ordos Basin is a crucial exploration field for natural gas, and exploration of the Ordovician middle assemblage (O1m55–7) has recently yielded great breakthrough. The Daniudi gas field provides a good case study to determine the gas source for the strata. The O1m55–7 gas displays C1/C1–5 ratios of 0.932?0.985 and CO2 contents of 1.56%?11.75%, and the detectable H2S content ranges from 0.0002% to 1.8617%. The δ13C1, δ13C2, δ13CCO2, and δD1 values are ?39.7‰ to ?35.6‰, ?30.4‰ to ?23.7‰, ?12.4‰ to ?4.6‰, and ?204‰ to ?185‰, respectively. Identification of the gas origin and source indicates that the gaseous alkanes are commonly coal-derived gas. The gas was generated from the coal measures in the Taiyuan Formation (C3t) and subsequently migrated. A small amount of oil-associated gas, mainly from O1m carbonate source rocks, has been incorporated into the gas reservoir. The natural gas has experienced insignificant alteration by thermochemical sulfate reduction, and the relatively high levels of CO2 are probably associated with corrosion alteration of carbonate reservoirs by injected fluid during acid fracturing.
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XU Hongyuan，BAI Chenyang，CHEN Wenlin，XU Xiaolei，WANG Yuhan，WANG Hongbin
2026,100(1):200-219, DOI: 10.1111/1755-6724.15356
Abstract:
The Dongsha area, a key target for gas hydrate exploration, is influenced by multiple factors, including sedimentary processes and the paleoenvironment, which play critical roles in gas hydrate formation. To elucidate the coupling among sedimentary processes, paleoenvironment, and gas hydrate accumulation, this study investigates the Site DS-W16 using particle size analysis, biological component content, and geochemistry data. Oxygen isotope data from foraminifera and biostratigraphic evidence indicate that sedimentation at the bottom of core interval from Site DS-W16 began during MIS 11 (Marine isotope stage). The sedimentation dynamics of the studied layers are complex, involving gravity flows, traction currents, and suspended deposition. Organic matter shows a significant correlation with transgressive–regressive cycle. The site DS-W16 contains two distinct gas hydrate reservoirs: a shallow reservoir (10–24 mbsf) and a deep reservoir (below 182 mbsf). The paleomarine environment influences gas hydrate accumulation by altering sedimentary processes and sediment characteristics, especially the distribution of biological components. Both shallow and deep gas hydrate reservoirs formed under dynamic conditions dominated by traction currents and are characterized by a higher abundance of foraminifera. Sedimentary layers rich in foraminifera and modified by traction currents represent key intervals for preferential gas hydrate accumulation.
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XIE Xiaoguo，ZHONG Ning，FU Siyi，ZHOU Huailai，LUO Bing
2026,100(1):220-230, DOI: 10.1111/1755-6724.70021
Abstract:
This study examines a 1.32 m thick sediment sequence from the Cunge sag pond in the Litang Basin, eastern Tibetan Plateau, to assess the seismicity of the Litang fault during the Holocene. High-resolution geochemical, grain size, magnetic susceptibility, and total organic carbon indicators are employed to obtain a continuous record of changes in elemental, physical, and biological properties within the profile to identify seismic events. The seismic event layer generally comprises two sedimentary rhythms: a lower coarse sand layer and an upper fine silt-clay layer. These layers represent rapid deposition associated with fault activity (Earthquake A) and slower deposition during calm periods or earthquake recurrence intervals (Seismic interval A). Through six 14C dating, five seismic events have been identified in the Cunge sag pond section: E1 (before 3955 a B.P.), E2 (3713–3703 a B.P.), E3 (3492–3392 a B.P.), E4 (2031–1894 a B.P.), and E5 (1384–1321 a B.P.). E1–E4 had shown a good consistency with the paleo-earthquake recorded by the trench, and whereas E5 is a newly identified seismic event, further improving the continuous earthquake sequence of the Litang fault. Based on existing trench data and the seismic event record from the Cunge sag pond, a total of 11 paleo-earthquakes are identified along the Litang fault since the Holocene. The paleo-earthquake activity of the Litang fault exhibits a clustered pattern, with recurrence intervals of both long periods (1000 a) and short periods (500 a). Since 5000 a, the interval between strong earthquake recurrences gradually decreases, indicating an increasing risk of strong earthquakes along the Litang fault. This study presents a continuous record of paleo-earthquakes along the Litang fault, eastern Tibetan Plateau, and can enhance the understanding of regional seismic activity.
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LAI Ya，LI Haibing，SI Jialiang，LI Chunrui，WANG Huan，ZHANG Lei，SUN Zhiming，ZHANG Jinjiang
2026,100(1):231-250, DOI: 10.1111/1755-6724.70014
Abstract:
The Guanxian–Anxian fault zone in the Longmen Shan, Sichuan, China, exhibits long-term creep-slip but ruptured during the 2008 Wenchuan earthquake, challenging the view that creeping faults rarely generate strong earthquakes. To investigate the transition from creep-slip to stick-slip, we analyzed fault rocks from the WFSD-3, using microstructural observations, XRD, μXRF, Raman spectroscopy, and quartz grain size statistics. Fault rocks show intense foliation, pressure-solution structures, and abundant clay minerals, reflecting long-term aseismic creep. At the interface between black and gray fault gouges at ~1249.98 m, microstructures indicate stick-slip behavior, including truncated grains, angular fragments, and finer grain sizes. Here, clay content drops sharply while strong minerals (quartz, feldspar, calcite, dolomite) increase. Elemental mapping shows Al and K enriched in black gouge, whereas Ca and Si in gray gouge; Raman spectroscopy indicates possible graphitization; the finest quartz grains occur in black gouge. These features mark co-seismic principal slip zone of the Wenchuan earthquake. We propose that fluid-driven transformation of strong minerals into clays facilitates creep-slip, whereas localized precipitation of strong minerals strengthens the fault, causing stress accumulation and controlling the creep-slip to stick-slip transition. This mechanism has implications for reassessing seismic hazards of creeping faults.
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ZHANG Lei，LI Haibing，SUN Zhiming，CAO Yong，XU Peng，LI Chunrui，WANG Huan，ZHENG Yong，SI Jialiang
2026,100(1):251-264, DOI: 10.1111/1755-6724.70026
Abstract:
The Yingxiu–Beichuan fault zone (YBFZ) has long been active and experienced repeated large earthquakes. The physicochemical properties of the deep fault zone (>1000 m) are the key to understanding the deformation mechanism of large earthquakes. This study uses rock magnetic, microstructural, and geochemical analyses of representative samples exposed in FZ1681 within the Wenchuan Earthquake Fault Scientific Drilling borehole 2 (WFSD-2) cores. Fault gouge and fault breccia have higher magnetic susceptibility values than wall rocks, and they contain abundant paramagnetic minerals and small quantities of magnetite and monoclinic pyrrhotite. The magnetite and monoclinic pyrrhotite in the fault gouge were mainly formed by coseismic frictional heating, indicating that large earthquakes with frictional heating temperatures of ~500–900℃ once occurred in the YBFZ. The seismogenic and coseismic environment was reducing with a relatively high sulfur content. The monoclinic pyrrhotite in the fault breccia was formed mainly by low-temperature hydrothermal fluid. This indicates that the fault zone experienced reducing and low-temperature (<400℃) hydrothermal fluid with a relatively high sulfur content after the earthquake. The YBFZ, which experiences frequent large earthquakes, is weakly oxidizing environment at different depths, but the effect of the low-temperature hydrothermal fluid is weaker at depth.
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QIU Dengfeng，HU Zongquan，John J. WALSH，GUO Jinrui，ZHANG Zhongming
2026,100(1):265-285, DOI: 10.1111/1755-6724.70015
Abstract:
The Western Sichuan Foreland Basin (WSFB) in South China, a prolific hydrocarbon province, exhibits complex structural deformation influenced by Triassic salt tectonics. This paper integrates seismic data and well data to elucidate the role of Middle–Lower Triassic evaporite layers in shaping basin structures, focusing on Xinchang Tectonic Zone (XTZ). Salt layers facilitated decoupled deformation between supra- and sub-salt sequences, forming salt pillows and fault-related folds. Three distinct structural trends were identified in XTZ. Key findings reveal that salt thickness variations correlate with deformation styles: thicker salt promoted detachment folding, while thinner salt led to hard-linked fault systems. Sub-salt E–NE trending reverse faults formed horsetail terminations associated with the Pengzhou faults (PzF), deviating from the primary Longmenshan thrust belt (LmsTB) orientation. Structural evolution occurred in three stages: (1) Indosinian salt deposition and foreland basin initiation; (2) Yanshanian eastward propagation of thrust systems with salt-driven detachment folding; (3) Himalayan reactivation overprinting earlier structures with sub-NS trending folds. This work establishes a direct link between salt layers and structural traps, demonstrating how salt acted as a critical detachment layer during multi-stage compression. Results provide insights into the gas exploration of the Late Triassic Xujiahe Formation, emphasizing the importance of salt-influenced deformation in foreland basin systems.
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WANG Siqi，ZHANG Baojian，LV Guosen，LIU Feng，ZHU Xi
2026,100(1):286-296, DOI: 10.1111/1755-6724.70036
Abstract:
The Mianhuakeng uranium deposit, characterized by uranium-rich granite, serves as a key site for research into crustal radioactive heating. Based on 45 rock samples, this study reviews that the host granite in the Mianhuakeng uranium deposit has a high radioactive heat production rate (avg. 5.50 μW/m3) and a low Th/U ratio (avg. 2.62). Uranium-rich granite and its alteration zone within the upper crust (0–5 km depth) contribute about 45% of the total radioactive heat production, wich is crucial for controlling geothermal resource distribution. For uranium-thermal at tectonic plate margins, a symbiotic geological model was proposed: Firstly, subduction of the Pacific Plate caused upwelling of the asthenosphere, generating a high heat flow background. Secondly, heat transfer is enhanced by major faults such as the Youdong and Mianhuakeng faults. Subsequently, uranium was mobilized, transported, and enriched within the granite through deep siliceous hydrothermal activity and associated alteration. Ultimately, the uranium enrichment in granite leads to increased radioactive heat production, resulting in local thermal anomalies. This model provides a theoretical support for exploring and developing uranium thermal symbiotic resources in South China.
2026年第100卷第1期
2026年第100卷第1期
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青藏高原东北缘祁连–海原断裂带中段金强河断裂晚第四纪滑动行为
梁淑敏, 郑文俊, 陈干, 张培震, 张冬丽, 毕海芸, 杨雪, 张逸鹏, 段磊, 卢本添
Abstract:
祁连–海原断裂带控制着青藏高原东北缘地区的强震活动。在其中段的金强河断裂是天祝地震空区一条关键的活动断裂，但目前对该断裂的滑动行为认识不足。本文针对沿金强河断裂的水平位移分布，利用WorldView-2立体像对和无人机摄影测量数据，提取断裂沿线高精度的DEM数据，并进行精细的构造地貌解译和水平位错测量。通过断错地貌标志的测量，得到135个位错量和8个位错丛集。同时，利用放射性碳测年方法构建4个典型点断错河流阶地的地貌单元年龄序列，从而通过位错与年龄的关系将位错丛集和地貌单元年龄序列关联起来，并获得金强河断裂全新世的滑动速率在 ~4–12 ka期间为4.8–5.6 mm/a ，在 ~4 ka以来为2.9–4.7 mm/a。最近的三次地震事件的复发间隔约为1000年，形成了一个地震活跃期，揭示着近1500年来缺乏破裂记录的金强河断裂可能具有较高的地震危险性。
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南阿尔金早古生代构造演化：来自茫崖花岗质岩石地球化学、锆石U-Pb和Lu-Hf同位素的证据
徐楠, 吴才来, 刘和武, 宋帅兵, 张贵生, 郑坤, 高栋
Abstract:
南阿尔金造山带是中国西南典型的俯冲造山带，由南阿尔金蛇绿混杂岩带和南阿尔金陆块组成，位于柴达木板块北侧。造山带出露大量早古生代花岗质岩石，但是这些岩石的成因及构造环境尚未查明。本文对茫崖花岗质岩石进行岩石学和地球化学研究，确定岩浆活动的期次，并深入了解南阿尔金造山带的构造演化过程。茫崖花岗质岩浆活动可以划分为三期：494-458Ma，450-436Ma和416-404Ma。根据这些岩石的成岩构造环境，我们认为第一期岩浆活动与南阿尔金洋的北向俯冲有关，形成了大量高价钙碱性、I型花岗质岩石。南阿尔金洋闭合后，柴达木板块开始向南阿尔金陆块碰撞，行了了一系列高价钙碱性、I型花岗岩。第三期岩浆活动形成了大量的造山后A-型花岗岩。
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超微量（80nanomole）硫化物硫酸盐硫同位素的EA-IRMS测试
Abstract:
常规EA-IRMS进行硫同位素测试时需硫量大于2 μmol，这限制了该技术在测试含硫量低的样品时的使用。如此大的需硫量是因为He载气携带样品气体在经过元素分析仪（EA）时的流速为~100 mL/min，而气体同位素质谱仪仅允许气体以低流速进入，所以99.7%的混合气体会通过连续流接口排出，以保证混合气体以~0.3 mL/min的流速通过连续流接口。因此，大部分的样品气体会被浪费，样品的利用率仅有0.3%。在本研究中，我们将自主研发的冷冻富集、分离与纯化系统与EA-IRMS联用测试了六种标准物质的硫同位素，并检测该系统的表现。实验结果表明，使用本研究中改进的方法进行硫化物和硫酸盐标准物质的硫同位素测试，得到的硫同位素结果与常规方法一致，即需硫量仅80 nmol即可得到硫同位素测试结果精度 ±0.24‰–±0.76‰ (1σ)，与使用吸附柱进行硫同位素测试的方法获得的精度相似。所以，改进后的EA-IRMS可以实现超微量硫化物、硫酸盐的硫同位素测试。此外，本方法也可应用至需样量低至100 nmol的碳、氮和氧同位素分析测试工作中。
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粤北早古生代强过铝质花岗岩及其共生岩石的岩石成因及对广西运动的指示意义：来自元素和Sr-Nd-Hf同位素的制约
Abstract:
本文系统报道了粤北地区早古生代强过铝质花岗岩及其共生岩石的锆石U-Pb年代学、主、微量元素及Sr-Nd-Hf同位素组成，探讨其源区特征、岩石成因及构造意义。青州花岗闪长岩为弱-强过铝质，A/CNK= 1.05–1.96。它们具有相对高的初始Sr同位素组成ISr= 0.7087– 0.7148和低的εNd(t)值(-11.2 – -10.1)，以及变化的εHf(t)值-13.4– +4.81。与之不同，大帽山花岗闪长岩为准铝质（A/CNK= 0.79– 0.94），ISr= 0.7083– 0.7110, εNd(t)= -7.92– -5.28和εHf(t)= -8.69– -2.06。高寿石英闪长岩为准铝-强过铝质（0.87– 1.24），ISr值和εNd(t)值分别为0.7104– 0.7111和-9.64– -8.63。元素和Sr-Nd-Hf同位素组成结果显示，青州、大帽山和高寿花岗质侵入岩主要分别源自变杂砂岩、英安质岩和角闪石岩的部分熔融。结合前人的研究成果，这些强过铝质花岗岩形成于同造山环境。本文尝试提出一种关于华南早古生代花岗岩的岩石成因及区域地壳重组的新思路。而广西运动动力机制的揭示需要更加广阔的视野和更加丰富的地质证据。
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Birendra P. Singh, Kapesa Lokho, Naval Kishore, Nancy Virmani
2014,88(2):380-393, DOI:
Abstract:
A new locality bearing ichnofossils of the Cruziana Assemblage Zone-III from the Mussoorie syncline, Lesser Himalaya, is located in rocks of Member-B of the Dhaulagiri Formation, Tal Group, exposed along the Maldewta-Chhimoli fresh road cut section. The site yielded ichnofossils Bergaueria perata, Cochlichnus anguineus, ?Diplocraterion isp., Dimorphichnus obliquus, diplichnitiform Cruziana bonariensis, Diplichnites gouldi, Glockeria isp., Helminthopsis isp., Monomorphichnus lineatus, Phycodes palmatum, Palaeophycus striatus, Planolites beverleyensis, Planolites montanus, Treptichnus cf. T. pedum, scratch marks and an undetermined worm impression. An Early Cambrian age (Cambrian Series 2) is assigned to the ichnofossil-bearing strata based on the stratigraphic position between the Drepanuroides and Palaeoolenus trilobite zones. A revised Cambrian ichnofossil zonation is presented for the Tal Group of the Mussoorie syncline. Together with their occurrence on rippled surfaces, and the lateral displacement of some trackways (due to current action), a sub-aqueous shallow-marine depositional setting is proposed for the rocks of Member-B.
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ZHU Song, WU Zhenhan, ZHAO Xitao, LI Jianping, WANG Hua
2012,86(1):266-283, DOI:
Abstract:
Many moraines formed between Daduka and Chibai in the Tsangpo River valley since Middle Pleistocene. A prominent set of lacustrine and alluvial terraces on the valley margin along both the Tsangpo and Nyang Rivers formed during Quaternary glacial epoch demonstrate lakes were created by damming of the river. Research was conducted on the geological environment, contained sediments, spatial distribution, timing, and formation and destruction of these paleolakes. The lacustrine sediments 14C (10537±268 aBP at Linzhi Brick and Tile Factory, 22510±580 aBP and 13925±204 aBP at Bengga, 21096±1466 aBP at Yusong) and a series of ESR (electron spin resonance) ages at Linzhi town and previous data by other experts, paleolakes persisted for 691~505 kaBP middle Pleistocene ice age, 75–40 kaBP the early stage of last glacier, 27–8 kaBP Last Glacier Maximum (LGM), existence time of lakes gradually shorten represents glacial scale and dam moraine supply potential gradually cut down, paleolakes and dam scale also gradually diminished. This article calculated the average lacustrine sedimentary rate of Gega paleolake in LGM was 12.5 mm/a, demonstrates Mount Namjagbarwa uplifted strongly at the same time, the sedimentary rate of Gega paleolake is more larger than that of enclosed lakes of plateau inland shows the climatic variation of Mount Namjagbarwa is more larger and plateau margin uplifted more quicker than plateau inland. This article analyzed formation and decay cause about the Zelunglung glacier on the west flank of Mount Namjagbarwa got into the Tsangpo River valley and blocked it for tectonic and climatic factors. There is a site of blocking the valley from Gega to Chibai. This article according to moraines and lacustrine sediments yielded paleolakes scale: the lowest lake base altitude 2850 m, the highest lake surface altitude 3585 m, 3240 m and 3180 m, area 2885 km2, 820 km2 and 810 km2, lake maximum depth of 735 m, 390 m and 330 m. We disclose the reason that previous experts discovered there were different age moraines dividing line of altitude 3180 m at the entrance of the Tsangpo Grand Canyon is dammed lake erosive decay under altitude 3180 m moraines in the last glacier era covering moraines in the early ice age of late Pleistocene, top 3180 m in the last glacier moraine remained because ancient dammed lakes didn’t erode it under 3180 m moraines in the early ice age of late Pleistocene exposed. The reason of the top elevation 3585 m moraines in the middle Pleistocene ice age likes that of altitude 3180 m. There were three times dammed lakes by glacier blocking the Tsangpo River during Quaternary glacial period. During other glacial and interglacial period the Zelunglung glacier often extended the valley but moraine supplemental speed of the dam was smaller than that of fluvial erosion and moraine movement, dam quickly disappeared and didn’t form stable lake.
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WANG Runfu, XU Shichao, WU Xiaochun, LI Chun, WANG Suozhu
2013,87(5):1185-1197, DOI:
Abstract:
Shansisuchus shansisuchus Young, 1964 was restudied on the basis of a new specimen. Some anatomical features that were either briefly or not described at all in the original study were detailed. The new specimen not only provides further information on the skull anatomy and the vertebral column but also expands the range of the geographical distribution of the taxon. With new information, the diagnosis of S. shansisuchus was emended and its phylogenetic relationships were further analyzed. S. shansisuchus differs from other archosauriforms primarily in the presence of a large subnarial fenestra anterior to the antorbital fenestra, tongue-in-groove articulations between the ascending process of the premaxilla and nasal and between the premaxilla and maxilla, a tall and posterodorsally directed ascending process of the maxilla, a knee-shaped process of the postorbital projecting into the orbit, a broad descending process of squamosal distally well forked and a large, deeply bow-shaped intercentrum tightly anchoring/capping the sharp ventral edges of two neighboring centra together in cervical and at least first eight dorsal vertebrae. With additional information derived from the new specimen, the phylogenetic relationships of S. shansisuchus were reanalyzed; it is closely related to Erythrosuchus-Vjushkovia clade.
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CHEN Lan1, 2, 3, * , YI Haisheng4, 5, TSAI Louis Loung-Yie2, XU Guiwen1, DA Xuejuan1, LIN Andrew Tien-Shun3
2013,87(2):540-554, DOI:
Abstract:
The Biluo Co and Amdo 114 station, northern Tibet, cropping out the Early Toarcian and Middle-Late Tithonian (Jurassic) organic-rich black shales, have been a focus to petroleum geologists in discussing their oil-producing potential. This paper first reports the trace elements and rare earth elements to discuss the paleoenvironments, redox conditions and sedimentary mechanisms of those black shales. Both sections exhibit variation in trace element abundances with concentrations <0.1 ppm to 760 ppm, mostly enriched in V, Cr, Ni, Cu, Zn, Mo, Ba and U. Element ratios of Ni/Co, V/Cr, U/Th and V/(V+Ni) plus U were used to identify redox conditions. The shale-normalized rare earth element (REE) patterns are characterized by the flat-shale type with instable Ce anomalies and very weekly positive Eu anomalies. Positive Ceanom values are significant with values varying between –0.064 and 0.029 in Biluo Co, which may be interpreted as release of REE and input of riverine terrestrial matter with rich Ce (resulting in pH change) during the anoxic conditions. In the middle parts of Amdo 114 station, distinct negative Ceanom values are observed (?0.238 to ?0.111) and associated surface water warming were interpreted as being related to a major sea level rise. In contrast, the formation of the black shales in the lower and upper part of the studied succession took place during a cooler (Ceanom values >–0.10), lower surface water productivity, and lower sea-level stage. Thus, we emphasize the role of different factors that control the formation of local and regional black shales. The most important factors are sea-level fluctuations and increasing productivity.
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SHEN Caizhi, Lü Junchang, LIU Sizhao, Martin KUNDRáT, Stephen L. BRUSATTE, GAO Hailong
2017,91(3):763-780, DOI:
Abstract:
A new troodontid dinosaur, Daliansaurus liaoningensis gen. et sp. nov., is erected based on a nearly complete specimen from the Lower Cretaceous Yixian Formation of Beipiao City, Liaoning Province, China. This well preserved skeleton provides important new details of the anatomy for Liaoning troodontids, and gives new insight into their phylogenetic relationships and evolution. Daliansaurus is distinguished from other troodontids by an enlarged ungual on pedal digit IV, which is approximately the same size as the sickle-shaped second ungual, and is differentiated from other Liaoning troodontids by a number of characters of the skull, manus, pelvis, and hindlimb. A phylogenetic analysis recovers Daliansaurus within a subclade of Liaoning troodontids that also includes Sinovenator, Sinusonasus, and Mei. We erect a name for this group—Sinovenatorinae—and argue that it reflects a localized radiation of small-bodied troodontids in the Early Cretaceous of eastern Asia, similar to previously recognized radiations of Liaoning dromaeosaurids and avialans. As more Liaoning theropods are discovered, it is becoming apparent that small, feathered paravians were particularly diverse during the Early Cretaceous, and future work is needed to clarify how this diversity arose, which species coexisted, and how these numerous species partitioned niches.
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2014,88(1):260-275, DOI:
Abstract:
This paper reviews the current progress and problems in the study of microbialites and microbial carbonates. Microbialites and microbial carbonates, formed during growth of microbes by their calcification and binding of detrital sediment, have recently become one of the most popular geological topics. They occur throughout the entire geological history, and bear important theoretical and economic significances due to their complex structures and formative processes. Microbialites are in place benthic microbial buildups, whereas microbial carbonates can be classified into two categories: stabilized microbial carbonates (i.e., carbonate microbialites, such as stromatolites and thrombolites) and mobilized microbial carbonates (i.e., microbial carbonate grains, such as oncoids and microbial lumps). Various texture, structures, and morphologies of microbialites and microbial carbonates hamper the systematic description and classification. Moreover, complex calcification pathways and diagenetic modifications further obscure the origin of some microbialites and microbial carbonates. Recent findings of abundant sponge spicules in previously identified “microbialites” challenge the traditional views about the origins of these “microbialites” and their implications to reef evolution. Microbialites and microbial carbonates did not always flourish in the aftermath of extinction events, which, together with other evidences, suggests that they are affected not only by metazoans but also by other geological factors. Their growth, development, and demise are also closely related to sea-level changes, due to their dependence on water depth, clarity, nutrient, and sunlight. Detailed studies on microbialites and microbial carbonates throughout geological history would certainly help understand causes and effects of major geological events as well as the co-evolution of life and environment.
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2014,88(z2):597-598, DOI:
Abstract:
Please refer to the attachment(s) for more details
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DU Chunguo, WANG Jianjun, ZHANG Jun, WANG Ping, XUE Mei, ZHOU Huayao
2014,88(3):865-877, DOI:
Abstract:
On the basis of field observations, microscopic thin-sections and laboratory data analysis of ten faults in Xuanhan County area, northeastern Sichuan Basin, central China, the internal and megascopic structures and tectonite development characteristics are mainly controlled by the geomechanical quality in brittle formation of the Changxing-Feixianguan Formation. The fluid transportation performance difference between the faults formed by different geomechanics or different structural parts of the same fault are controlled by the megascopic structure and tectonite development characteristics. For instance, the extension fault structure consists of a tectonite breccia zone and an extension fracture zone. Good fluid transportation performance zones are the extension fracture zone adjacent to the tectonite breccia zone and the breccia zone formed at the early evolutionary stage. The typical compression fault structure consists of a boulder-clay zone or zones of grinding gravel rock, compression foliation, tectonite lens, and dense fracture development. The dense fracture development zone is the best fluid transporting area at a certain scale of the compression fault, and then the lens, grinding gravel rock zone and compression foliation zones are the worst areas for hydrocarbon migration. The typical tensor-shear fault with a certain scale can be divided into boulder-clay or grinding gravel rock zones of the fault, as well as a pinnate fractures zone and a derivative fractures zone. The grinding gravel rock zone is the worst one for fluid transportation. Because of the fracture mesh connectivity and better penetration ability, the pinnate fractures zone provides the dominant pathway for hydrocarbon vertical migration along the tensor-shear fault.
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MA Shengming, ZHU Lixin, LIU Chongmin, XI Mingjie, TANG Shixin
2013,87(3):843-857, DOI:
Abstract:
This paper discusses the enrichment and depletion regularities for porphyry copper-molybdenum ore deposits in different regions and varied deposit genetic types in the same area, taking three porphyry copper-molybdenum ore deposits (i.e., the Chengmenshan in Jiangxi, Wunugetushan in Inner Mongolia, Baishantang in Gansu) and two copper deposits in Gansu Province (the Huitongshan skarn deposit and Gongpoquan composite deposit) as case studies. The results show that porphyry Cu-Mo deposits or skarn copper deposits include both enrichment of the ore-forming elements and associated elements, and depletion of some lithophile dispersed elements, rare earth elements (REE) and some major elements. And the depleted elements vary with deposits, having generality and their own features. On a deposit scale, the positive anomalies of enriched elements and negative anomalies of depleted elements follow in a sequence to comprise regular anomaly models of spatial structures. The exploration in the Tongchang deposit in Jiangxi and Huitongshan deposit in Gansu suggests that anomaly models play a key role in the identification of mineral occurrences and deposits compared to one single enriched element anomaly. And the anomaly models exert a critical effect on the optimization of prospecting targets and their potential evaluation.
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2010,84(2):241-246, DOI:
Abstract:
A new boreopterid pterosaur: Zhenyuanopterus longirostris gen. et sp. nov. from the Yixian Formation of western Liaoning is erected, based on the complete skeleton with a skull and lower jaws preserved. It is characterized by: a large boreopterid pterosaur with a high number of teeth, where the anterior teeth are much larger than posterior ones; the length of the dorsal + sacral vertebrae is nearly half the length of the skull; ratio of the length of the humerus to metacarpal IV is approximately 91% and the, humerus, femur and third wing phalanx are all equal in length and the feet are specially small. It represents the largest boroepterid pterosaur discovered from western Liaoning and its surrounding areas so far
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WANG Sufen, ZHANG Tingshan, ZHOU Jixian, HU Yu
2017,91(1):320-340, DOI:
Abstract:
The distribution characteristics of the oil-water contact are the basis for the reservoir exploration and development and reserves evaluation. The reservoir with a tilted oil-water contact has a unique formation mechanism, and the understanding of its distribution and formation mechanism will directly affect the evaluations for the reservoir type, well deployment, selection of well pattern and type, determination of test section, and reserves evaluation. Based on the analysis of reservoir characteristics, petrophysical properties and geological structure in 40 reservoirs worldwide with tilted oil-water contacts, the progress of the research on the formation mechanisms of titled oil-water contacts is summarized in terms of the hydrodynamic conditions, reservoir heterogeneity, neotectonic movement and oil-gas exploitation. According to the formation mechanism of tilted oil-water contacts and the needs of exploration research, different aspects of research methods are summarized and classified, such as the calculation of equipotential surfaces for oil and water in the formation, analysis of formation pressure and analysis of reservoir physical properties and so on. Based upon statistical analysis, it is suggested that the degree of the inclination of the oil-water contact be divided based on the dip of oil-water contact (DipTOWC). The tilted oil-water contact is divided into three categories: large dip (DipTOWC≥55 m/km), medium dip (4 m/km≤DipTOWC<55 m/km), and small dip (DipTOWC<4 m/km). The classification and evaluation method can be combined with structure amplitude and reservoir property. The formation mechanism of domestic and international reservoirs with tilted oil-water contacts are summarized in this paper, which have important significance in guiding the exploration and development of the oilfield with tilted oil-water contacts, reserves evaluation, and well deployment.
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Mahboobeh JAMSHIDI BADR, Fariborz MASOUDI, Alan S. COLLINS, Ali SORBI
2012,86(1):48-64, DOI:
Abstract:
The Soursat metamorphic complex (SMC) in northwestern Iran is part of the Sanandaj–Sirjan metamorphic belt. The complex is composed of different metamorphic and plutonic rocks, but is dominated by metapelites composed of garnet, staurolite, kyanite, fibrolite, cordierite, and andalusite. Porphyroblasts in schists have the same fabric, and three stages of schistosity are present. The internal schistosity (Sn) inclusion trails are also offset by conjugate sets of extensional schistosity (Sn+1) and a second (Sn+2) that crenulates (Sn+1). Polyphase metamorphisms are present in the complex. Garnet, staurolite, kyanite, and fibrolite assemblage preserves conditions during the M1 metamorphic event. This assemblage yields a P–t estimate of 645±11°C and 6.5±0.5 kbar. Other samples of the central part of SMC contain cordierite and andalusite (M2) overgrowth that yields a P–t estimate of 532±33°C and 2.1±1.1 kbar.
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ZHENG Yadong, ZHANG Qing, HOU Quanlin
2015,89(4):1133-1152, DOI:
Abstract:
The essential difference in the formation of conjugate shear zones in brittle and ductile deformation is that the intersection angle between brittle conjugate faults in the contractional quadrants is acute (usually ~60°) whereas the angle between conjugate ductile shear zones is obtuse (usually 110°). The Mohr-Coulomb failure criterion, an experimentally validated empirical relationship, is commonly applied for interpreting the stress directions based on the orientation of the brittle shear fractures. However, the Mohr-Coulomb failure criterion fails to explain the formation of the low-angle normal fault, high-angle reverse fault, and the conjugate strike-slip fault with an obtuse angle in the σ1 direction. Although it is ten years since the Maximum-Effective-Moment (MEM) criterion was first proposed, and increasingly solid evidence in support of it has been obtained from both observed examples in nature and laboratory experiments, it is not yet a commonly accepted model to use to interpret these anti-Mohr-Coulomb features that are widely observed in the natural world. The deformational behavior of rock depends on its intrinsic mechanical properties and external factors such as applied stresses, strain rates, and temperature conditions related to crustal depths. The occurrence of conjugate shear features with obtuse angles of ~110° in the contractional direction on different scales and at different crustal levels are consistent with the prediction of the MEM criterion, therefore ~110° is a reliable indicator for deformation localization that occurred at medium-low strain rates at any crustal levels. Since the strain–rate is variable through time in nature, brittle, ductile, and plastic features may appear within the same rock.
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CHI Guoxiang1, *, CHU Haixia1, Ryan SCOTT1, CHOU I-Ming2
2014,88(4):1169-1182, DOI:
Abstract:
Raman peaks of various hydrates in the H2O-NaCl-CaCl2 system have been previously identified, but a quantitative relationship between the Raman peaks and XNaCl (i.e., NaCl/(NaCl+CaCl2)) has not been established, mainly due to the difficulty to freeze the solutions. This problem was solved by adding alumina powder to the solutions to facilitate nucleation of crystals. Cryogenic (-185oC) Raman spectroscopic studies of alumina-spiced solutions indicate that XNaCl is linearly correlated with the total peak area fraction of hydrohalite. Capsules of solutions made from silica capillary were prepared to simulate fluid inclusions. Most of these artificial fluid inclusions could not be totally frozen even at temperatures as low as -185oC, and the total peak area fraction of hydrohalite is not correlated linearly with XNaCl. However, the degree of deviation (DXNaCl) from the linear correlation established earlier is related to the amount of residual solution, which is reflected by the ratio (r) of the baseline “bump” area, resulting from the interstitial unfrozen brine near 3435 cm-1, and the total hydrate peak area between 3350 and 3600 cm-1. A linear correlation between DXNaCl and r is established to estimate XNaCl from cryogenic Raman spectroscopic analysis for fluid inclusions.
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LI Jianjun, Martin G. LOCKLEY, ZHANG Yuguang, HU Songmei, MATSUKAWA Masaki, BAI Zhiqiang
2012,86(1):1-10, DOI:
Abstract:
A large track site with multiple, well-preserved trackways of an Early Jurassic quadrupedal ornithischian dinosaur is the first report of Moyenisauripus-like trackways from Asia, herein named Shenmuichnus youngteilhardorum. The tracks occur in a clastic fluvial sequence in the Fuxian Formation in Shenmu County, Shaanxi Province, which is in the same general region as the discovery site of Sinoichnites，the first dinosaur track reported from China. Based on size and morphology, it is likely that Sinoichnites, which is now lost, also represents an ornithischian. The Shenmuichnus youngteilhardorum trackways show two modes of preservation: the first representing deeper tracks, with sediment rims, results in Deltapodus-like tracks, with indistinct pes digit traces and sub-circular manus traces, the second produces Moyenosauripus-like tracks, with clear tridactyl and pentadactyl digit traces in the pes and manus respectively. Thus the Shenmu trackways play a key role in resolving globally significant ichnotaxonomic problems surrounding the nomenclature of Sinoichnites, Moyenosauripus, Deltapodus and other named (Ravatichnus) and unnamed trackways from Asia, Africa and Europe. In addition they shed important light on the paleogeographical and paleoecological distribution of quadrupedal ornithischians in the Early Mesozoic. The track site has been the focus of a major excavation to transfer the trackways from their original remote location to the new Shenmu Museum, in Shenmu City. Other tracksites in the area which reveal Anomoepus, Grallator and the Deltapodus morphotype, together with Shenmuichnus and plant fossil evidence, suggest an Early Jurassic age for the tracksite.
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DU Jianjun, LI Dunpeng, WANG Yufang, MA Yinsheng
2017,91(1):76-92, DOI:
Abstract:
The Weihe Graben is not only an important Cenozoic fault basin in China but also a significant active seismic zone. The Huashan piedmont fault is an important active fault on the southeast side of the Weihe Graben and has been highly active since the Cenozoic. The well–known Great Huaxian County Earthquake of 1556 occurred on the Huashan piedmont fault. This earthquake, which claimed the lives of approximately 830000 people, is one of the few large earthquakes known to have occurred on a high–angle normal fault. The Huashan piedmont fault is a typical active normal fault that can be used to study tectonic activity and the associated hazards. In this study, the types and characteristics of late Quaternary deformation along this fault are discussed from geological investigations, historical research and comprehensive analysis. On the basis of its characteristics and activity, the fault can be divided into three sections, namely eastern, central and western. The eastern and western sections display normal slip. Intense deformation has occurred along the two sections during the Quaternary; however, no deformation has occurred during the Holocene. The central section has experienced significant high–angle normal fault activity during the Quaternary, including the Holocene. Holocene alluvial fans and loess cut by the fault have been identified at the mouths of many stream valleys of the Huashan Mountains along the central section of the Huashan piedmont fault zone. Of the three sections of the Huashan piedmont fault, the central section is the most active and was very active during the late Quaternary. The rate of normal dip–slip was 1.67–2.71±0.11 mm/a in the Holocene and 0.61±0.15 mm/a during the Mid–Late Pleistocene. As is typical of normal faults, the late Quaternary activity of the Huashan piedmont fault has produced a set of disasters, which include frequent earthquakes, collapses, landslides, mudslides and ground fissures. Ground fissures mainly occur on the hanging–wall of the Huashan piedmont fault, with landslides, collapses and mudslides occurring on the footwall.
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2015,89(3):715-725, DOI:
Abstract:
Re-equilibration of fluid inclusions in crystals takes place by loss or gain of solvents and solutes from fluid inclusions and by changes in their volumes. Volume change of fluid inclusions are primarily dictated by elastic properties and available slip planes of host crystals. In the present study, the phase-behavior of fluids entrapped in co-precipitated calcite and barite is studied. While calcite contains only biphase fluid inclusions, barite has predominantly monophase fluid inclusions. Fluid inclusion petrography, microthermometry and leachate analysis are used to establish the nature of entrapped fluids and entrapment temperature is substantiated through independent sulfur isotope geothermometry using coexisting barite and pyrite. Phase transitions in the monophase fluid inclusions in barite are explained in terms of over-pressuring of fluids in these fluid inclusions relative to fluids entrapped in calcite owing to the low bulk modulus of barite.
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ZHANG Gang, WANG Xuben, FANG Hui, GUO Ziming, ZHANG Zhaobin, LUO Wei, CAI Xuelin, LI Jun, LI Zhong, WU Xing
2015,89(2):531-541, DOI:
Abstract:
The Panxi region is located in the frontal zone of positive squeezing subduction and side squeezing shearing between the Indian plate and the Eurasian plate. The long-period magnetotelluric (LMT) and broadband magnetotelluric (MT) techniques are both used to study the deep electrical conductivity structure in this region; magnetic and gravity surveys are also performed along the profile. According to the 2-D resistivity model along the Yanyuan-Yongshan profile, a high-conductivity layer (HCL) exists widely in the crust, and a high-resistivity block (HRB) exists widely in the upper mantle in general, as seen by the fact that a large HCL exists from the western Jinpingshan tectonic zone to the eastern Mabian tectonic zone in the crust, while the HRB found in the Panxi tectonic zone is of abnormally high resistivity in that background compared to both sides of Panxi tectonic zone. In addition, the gravity and magnetic field anomalies are of high value. Combined with geological data, the results indicate that there probably exists basic or ultrabasic rock with a large thickness in the lithosphere in the Panxi axial region, which indicates that fracture activity once occurred in the lithosphere. As a result, we can infer that the high-resistivity zone in the Panxi lithosphere is the eruption channel for Permian Emeishan basalt and the accumulation channel for basic and ultrabasic rock. The seismic sources along the profile are counted according to seismic record data. The results indicate that the most violent earthquake sources are located at the binding site of the HRB and the HCL, where the tectonic activity zone is generally acknowledged to be; however, the earthquakes occurring in the HCL are not so violent, which reflects the fact that the HCL is a plastic layer, and the fracture threshold of a plastic layer is low generally, making high stress difficult to accumulate but easy to release in the layer. As a result, a higher number of smaller earthquakes occurred in the HCL at Daliangshan tectonic zone, and violent earthquakes occurred at the binding site of high- and low-resistivity blocks at the Panxi tectonic zone.
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2021,95(3):1056-1056, DOI: 10.1111/1755-6724.14310
Abstract:
