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The response relationship between the sedimentary model and tectonic deformation of the Cambrian Gaotai Formation in eastern Sichuan and its significance in oil and gas geology

Feng Xukui, Chen Youzhi

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Previous studies have paid limited attention to both the intrinsic deformation mechanisms of the evaporite-bearing sequences within the Cambrian Gaotai Formation in eastern Sichuan and the relationship between sedimentary facies distribution and salt tectonic deformation. Consequently, the location of grain shoals along the margins of salt sags within the Gaotai Formation cannot be constrained, which has hindered petroleum exploration targeting this formation. To address these issues, this study integrates structural interpretation of seismic reflection profiles from the north-central part of eastern Sichuan, numerical simulation of structural deformation, fold uplift age data, drilling data, and thickness information of the overlying Xixiangchi Formation. This multi-faceted approach was used to investigate the development mechanisms of Gaotai Formation salt structures, the response relationship between salt tectonic deformation and original deposition, and to summarize the characteristics of favorable zones for grain shoal facies along the Gaotai Formation salt depression margins. The results indicate that: (1) The synclinal zone corresponds to the marginal zone of the saline depression during the depositional period of the Gaotai Formation, while the anticlinal area matches either the center of the saline depression or the facies transition zone between the saline depression and its margin. (2) The primary mechanisms for salt structure development in the salt depression areas are contraction and buoyancy forces. (3) The incongruous folds beneath the Gaotai Formation within the synclinal areas represent favorable zones for hydrocarbon accumulation.
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MATHEMATICAL RELATION BETWEEN THE EXCESS AREA WITH DEPTH TO DETACHMENT AND CRESTAL STRUCTURAL RELIEF OF DETACHMENT FOLDS

yanggeng, CHEN Zhuxing, Ren Rong, Su Nan

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Detachment folds seem conceptually and geometrically the simplest of all fault-related folds, and researches on them mainly focuses on geometric analysis and genesis mechanisms. Detachment folds are defined by competent rocks units and are cored by incompetent units deformed internally above a detachment horizon.Many detachment folds may analyzed using a simple geometric model. Early mathematical triangle’s models of detachment fold were developed into various geometric models, and the theoretical calculation of the excess area of these fold models is only related to the length and dipping angle of the fold limbs. However, in practical applications, the area-depth-strain (ADS) methods is widely used to calculate the depth to detachment, shortening, and parallel strain of the formation, indicating a disconnect between theoretical models and practical applications. Based on this, this article establishes a theoretical relationship between the excess area of concentrated special types of detachment folds, such as box fold,lift-off fold,symmetric fold and asymmetric fold, and the depth to detachment. Based on the definition of excess area and depth to detachment in the deformation of detachment folds, assuming a constant thickness of the stratum and known height of the fold core structure (Crestal Structural Relief) and strata dip angles of the fold-limbs, this paper establishes the mathematical relationship between excess area and depth to detachment of different structural geometric styles of Swiss Jura detachment folds, such as box shaped detachment folds, lift-off detachment folds, symmetrical detachment folds with limbs dip angles, and asymmetrical detachment folds with limbs dip angles. A fast calculation method for the shortening of detachment fold deformation and depth to detachment is obtained. It should be noted that according to the principles of geometry, the geometric shape of box-shaped detachment folds remains basically unchanged, while the geometric shape of lift-off detachment folds transform upwards into chevron folds. Symmetric folds and asymmetric folds, due to the presence of a basal incompetent plastic layers, have different mathematical relationships between their excess area and the depth to detachment above and below specific fold deformation layer. It is referred to as a transition layer or Detachment Conversion Layer(DCL). In addition to differences in geometric styles, the deformation mechanisms of this transition layer also differs.
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Geometry and kinematics of strike-slip fault related structural patterns and their metallogenetic effects

CHEN Xuanhua, HAN Lele, ZHANG Yiping, WANG Ye, MA Feizhou, DING Weicui, SU He, XU Shenglin

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Large-scale strike-slip faults developed at plate or terrane boundaries and intra-plate tectonic settings, serving as a prominent feature of tectonic deformation on the Earth""s surface. They can be categorized into convergent and divergent strike-slip faults. Based on previous studies on strike-slip fault-related structures, this study proposes a new classification system for them. The proposed framework divides strike-slip fault-related folds into three end-members, i.e., strike-slip fault-bend folds, strike-slip fault-propagation folds, and strike-slip detachment folds, along with composite styles of strike-slip interference folds, and establishes their geometric and kinematic models. The study introduces two new types of lotus-shaped superimposed folds related to strike-slip faulting, namely the Kulumudishan-type and Maidoushan-type superimposed folds, along with their formation mechanisms, and elucidates the developing process of strike-slip growth anticlines. It is concluded that strike-slip fault-related structures can serve as significant kinematic indicators for strike-slip faults. Using the West Junggar Orogenic Belt in Central Asia as an example, the study elucidates how the strike-slip fault activity controlled on the migration, concentration, and metallogenic effects of ore-forming elements through tectono-physicochemical processes.
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Multistage Mesozoic Exhumation–Erosion Processes and Tectono-Sedimentary Coupling in the Southern Margin of the Micang Mountain, South China

Zhang Mengfei, Qiu Nansheng, Chang Jian, Feng Qianqian, Li Chenxing, Liu Xin, Long Kangjie

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The formation of the Micang Mountain Uplift is closely related to plate collision and the uplift of the Qinling Orogenic Belt. Previous research has predominantly focused on its uplift-erosion processes since the Middle-Late Mesozoic, though there remains controversy regarding its specific uplift process. This study selected Precambrian samples from the southern margin of the Micang Mountain Uplift to conduct low-temperature thermochronology experiments, combined with detrital zircon U-Pb age data from Mesozoic strata in the region, to systematically reconstruct the multi-stage uplift-erosion history since the Early Mesozoic. The research results show that the median age range of zircon fission tracks is 277±27Ma to399±39Ma, while the zircon (U-Th)/He age range is 136.4±6.8Ma to 290.0±14.5Ma. Through thermal history simulation, the tectonic evolution of the Micang Mountain Uplift since the Mesozoic can be divided into four stages: 1) from the Late Triassic to the Middle Jurassic, affected by the closure of the Mianlue Ocean and the subduction of the Yangtze Block under the Qinling Block, the Micang Mountain region began an initial slow uplift; 2) from the Late Jurassic to the Early Cretaceous, the continuous collision between the Qinling Block and the Yangtze Block triggered intense intracontinental orogeny, leading to rapid uplift of the Micang Mountain region; 3) from the Late Cretaceous to the Neogene Miocene, the region entered a brief tectonic quiescence period due to adjustments in regional plate movements; 4) since the Miocene, affected by the eastward propagation of the Tibetan Plateau’s uplift, the region has experienced another phase of rapid uplift and denudation. Detrital zircon U-Pb age spectra indicate a significant increase in Neoproterozoic zircons in the strata from the Upper Triassic to the Lower Jurassic, indicating that uplift had already initiated in the Late Triassic, which aligns well with the initial uplift timing indicated by low-temperature thermochronology data. This study reconstructs the tectono-thermal evolutionary history of the southern margin of the Micang Mountain Uplift since the Mesozoic, clarifies the temporal and spatial coupling relationship between the multi-stage uplift-erosion processes and multi-episodic plate tectonic movements, and provides new evidence for understanding plate collision dynamics and Qinling Orogen evolution
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Vertical Interweaving Superimposed Structures: Distinct Features of Cratonic Basins in China

He Dengfa, Jia Chengzao, Zhao Zhe, Zhao Luzi, Bao hongping, Gao Shanlin, Lu Guo, Zheng Na, Yang ZhiKun, Cheng Changyu

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The cratonic basins in China are multi-cycle superimposed basins entitled of the spatial-temporal combination of proto-type basins during the different geological periods. To explore the spatial superimposed combinations of the structural units of the proto-type basins (such as uplift, sag, and slope etc.) with the geological history is not only the crucial basis for recognizing the geological structure features of the basin, but also the key step for discussing the distribution of oil and gas accumulation. Based upon the new drilled deep-boreholes and the recent-acquired high-resolution reflective seismic data, the paper disclosed the vertical structural features and hydrocarbon plays of the cratonic basins in China. The vertical superimposition of the overlying and underlying different orientation structure of the cratonic basin in China is here called as the “vertical interweaving superimposed structure”. It has nine basic types according to the superimposing style of the overlying unit over the underlying unit, that is, the six types in the interior such as, uplift over rift trough, sag over uplift, anticlinal belt over sag, sag over sag, as well as slope over sag, and the three types in the margin such as, rift belt over uplift, thrust belt over faulted-sag, and fold-and-thrust belt over passive continental margin. The geological framework controls on the three types of oil and gas accumulation models such as, the nearby sourced and lateral reservoir, the underlying sourced and overlying reservoir, and the source-reservoir by itself. The oil and gas migrated from the source kitchen crossing the different strata, during the different periods, into the large-scale accumulation zone or belt, which formed the orderly plays of the conventional-and-unconventional resources (including the shale oil and gas , and the coal-stone gas). A series of super-giant and giant oil and gas fields have been recently found in cratonic basins in China, e.g. An Yue, Penglai, Puguang, Yuanba, Jiaoshiba, Changning, Dabei-Keshen, Tahe-Lunnan, Shunbei-Fuman, Jingbian, Sulig, Hengshan, and Qingcheng gas or oil fileds. The vertical interweaving superimposed structures greatly improved the chance for oil and gas pool-formation.
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Comparison of Geochronological Methods for Uranium-rich Granites: A Case Study from the Ziyunshan Uranium-rich Granite in Central Jiangxi Province*

Huang Chao, Li Guanglai, Yang Yongle, Meng Siyuan, Zhong Zhaoxuan, Zhou Maoqiang, Xu Kai, Liu Xiaodan

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Zircon in uranium-rich granites frequently undergoes intense metamicization owing to elevated uranium content, resulting in unreliable U-Pb dating outcomes and complicating the accurate determination the U-Pb age of zircon from such granite. To tackle the challenges associated with precise dating of high-uranium granites, this study investigates the Ziyunshan pluton in central Jiangxi. Comprehensive petrographic and petrochemical analyses were performed, confirming its classification as a typical uranium-rich peraluminous granite. Using α-track etching technology, uranium-bearing minerals were identified and characterized through scanning electron microscopy and electron probe analysis. These analyses revealed primary magmatic minerals, including zircon, monazite, xenotime, and uraninite, alongside hydrothermal secondary minerals such as coffinite and thorite. Geochronological investigations of the principal uranium-bearing minerals indicated that zircon, affected by intense metamicization, produced scattered and anomalously young LA-ICP-MS U-Pb ages (142.8 ± 1.0 Ma), suggesting an open isotopic system. In contrast, monazite yielded a weighted average age of 150.5 ± 0.8 Ma, which is both consistent and reliable. Additionally, the electron probe U-Th-Pb chemical age of uraninite was determined as 151.4 ± 1.7 Ma, aligning with previously established rock formation ages. This study demonstrates that monazite, owing to its strong radiation resistance and robust isotopic system, can serve as an effective alternative to zircon for dating uranium-rich granites. Furthermore, electron probe chemical dating of uraninite proves to be a feasible and accurate method, offering valuable insights for geochronological studies of similar granite.
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U-Pb Baddeleyite Ages of Diabase Dykes Constrain the Mesoproterozoic Chronostratigraphic Attribution of the Longshan Formation, North China Craton

Zhang Yunqiang), Kuang Hongwei, Liu Yongqing, Wang Yuchong), Peng Nan), Chen Zhaohong, Zhou Qifeng), Li Ruihong), Wang Zhimin), Hao Sen)

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One of the significant research progresses on the Meso-Neoproterozoic strata in the Yanliao area of North China is the discovery of the Yanliao Large Igneous Province (YLIP) (at ~1325 Ma). However, previous studies suggested that the YLIP was only emplaced in the Xiamaling Formation and did not intrude into the stratigraphic horizons above the Xiamaling Formation. In recent years, however, the authors have successively discovered diabase sills intruding into the Longshan Formation in the Yanliao area. To clarify whether these diabases have a genetic relationship with the YLIP, and to constrain the chronostratigraphic attribution of the Longshan Formation—for which reliable ages have been lacking for more than half a century—through zircon dating of the diabases, this study conducted dating analyses on baddeleyite from the diabases intruding the Longshan Formation using SIMS (Secondary Ion Mass Spectrometry) and SHRIMP (Sensitive High-Resolution Ion Microprobe) methods, respectively. The SIMS method yielded a weighted mean 2??Pb/2??Pb age of 1322±8 Ma for baddeleyite, while the SHRIMP method obtained a weighted mean 2??Pb/2??Pb age of 1304±8 Ma. The results from the two dating methods are highly consistent and fully match the age peak of the YLIP reported in previous studies. Based on these dating results, combined with comprehensive research and comparison of the spatio-temporal distribution, intrusive contact relationships, and rare earth element (REE) distribution patterns between the diabases intruding the Longshan Formation and the YLIP, this study concludes that the diabases intruding the Longshan Formation should be part of the YLIP. Furthermore, this dating result defines the stratigraphic age of the Longshan Formation as the Mesoproterozoic, predating 1322–1304 Ma. This research achieves a breakthrough in the study of the chronostratigraphic attribution of the "Meso-Neoproterozoic" Longshan Formation in North China, a puzzle that has persisted for nearly half a century. It also provides new evidence and age constraints for in-depth understanding of whether the evolution of algae or eukaryotic microorganisms since the Proterozoic follows the "Boring Billion" (1.8–0.8 Ga) evolutionary pattern. Meanwhile, it expands the spatio-temporal scope of the YLIP.
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The quantity-scale-grade structure and temporal-spatial distribution of magmatic vanadium-titanium magnetite ore deposits in China

LI Houmin, LI Lixing, LI Xiaosai, Wu Xuan, MENG Jie

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Magmatic vanadium-titanium magnetite deposits are hosted in mafic-ultramafic intrusions.This type of deposits represent the second important source of iron, and contains valuable associated resources such as titanium, vanadium, cobalt, nickel, and phosphorus.A total of 231 magmatic vanadium-titanium magnetite deposits have been identified in China, including 4 super-large-scale, 17 large-scale, and 49 medium-scale ones.Statistics show that the overall ore grade of magmatic vanadium-titanium magnetite ores is relatively low: Ore occurrences with a TFe grade of 25～45% account for 53% of the total number of occurrences and 64% of the total iron ore reserves; Those with a TFe grade of 20～25% make up 16% of the total occurrences and 24% of the total reserves; Ore occurrences with a TFe grade below 20% constitute 27% of the total number of occurrences but only 12% of the total reserves.Although there are only 4 super-large-scale ore deposits, they contribute 72% of the total iron ore reserves.Large-scale ore deposits, accounting for 9% of the total number of occurrences, represent 19% of the total reserves.This indicates that large-scale and super-large-scale deposits play a pivotal role in magmatic iron ore resources.In terms of temporal distribution, magmatic vanadium-titanium magnetite mineralization occurred from the Archean to the Mesozoic.However, the Permian Panzhihua-type iron deposits occupy an absolutely dominant position, followed by the Mesoproterozoic Damiao-type iron deposits.In terms of spatial distribution, magmatic iron ore occurrences have been found in 22 provinces (autonomous regions and municipalities) across the country.Nevertheless, their quantity and ore reserves are concentrated in the III-76 Kangdian Uplift Fe-Cu-V-Ti-Sn-Ni-REE-Au-crocidolite-saline metallogenic belt in the Panzhihua-Xichang area of Sichuan Province and the III-57 Eastern Segment of the Northern Margin of the North China Craton Fe-Cu-Mo-Pb-Zn-Ag-Mn-U-phosphorus-coal-bentonite metallogenic belt in the Chengde area of Hebei Province.In addition, the Ankang-Hanzhong area in Shaanxi, the Yishui-Juxian area in Shandong, and the Tarim Basin and its adjacent areas in Xinjiang are also relatively important.The mineralization of magmatic vanadium-titanium magnetite deposits is all related to major tectono-magmatic events under extensional settings.Examples include the Emeishan mantle plume (associated with Panzhihua-type iron deposits) and the 1.8-1.7 Ga supercontinent rifting event of the North China Craton (related to Damiao-type iron deposits).
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Interpretable Machine learning-Based intelligent discrimination of Rhyolite Tectonic Settings

He Yuxing, He Haiyang, Xu Tangxing, Li JianXiong, Shen Qinqin, Zhang Huanbao, Liu Ke, Li Penggang, Li Xiangcheng

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The discrimination of tectonic settings for rhyolites holds significant importance in geodynamic research. However, traditional graphical methods, constrained by low-dimensional parameter spaces and the influence of post-emplacement alteration, struggle to effectively resolve complex magmatic genetic mechanisms, leading to uncertainties in tectonic discrimination results. In recent years, machine learning (ML) techniques have been widely applied in Earth sciences, with intelligent identification of tectonic settings based on multi-dimensional geochemical feature analysis and pattern mining emerging as a critical research direction. This study utilizes the global rhyolite geochemical database (GEOROC) to establish a systematic dataset comprising 5,874 high-quality rhyolite samples, incorporating 46 parameters including major, trace, and rare earth element (REE) concentrations and ratios. Nine ML classifiers were developed, encompassing ensemble tree models (XGBoost, LightGBM, CatBoost), support vector machines (SVM), and deep learning architectures (MLP, TabPFN), with hyperparameters optimized via the Optuna algorithm to enhance model performance. Experimental results demonstrate that the Transformer-based TabPFN model achieved optimal performance without hyperparameter tuning, attaining a test-set accuracy of 88.37% and AUC value of 98.39%, highlighting its superiority in geochemical data learning. The optimized LightGBM model exhibited an improved average accuracy of 87.98%, confirming the efficacy of hyperparameter optimization. Interpretability analyses using SHAP (SHapley Additive exPlanations) and LIME (Local Interpretable Model-agnostic Explanations) identified critical discriminators including Cs, Hf, and Th/Ta ratios, whose contributions correlate closely with geodynamic processes such as subduction-related fluid activity, mantle partial melting, and crust-mantle interactions. Meanwhile, trace elements traditionally overlooked in conventional studies (e.g., Ga, Co) exhibited significant classification power, suggesting the potential value of multi-element synergy analysis in tectonic discrimination. This research demonstrates that integrating high-dimensional geochemical data with interpretable ML models substantially enhances tectonic setting identification accuracy, providing a novel methodology for determining the tectonic affinity of felsic magmatic rocks and advancing regional geodynamic evolution studies.
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Genesis of the Shaliuhe chromite body in the Northern Qaidam Orogen: Evidence from in-situ mineral and whole-rock elemental compositions

Zhuang Wu, Hongfu Zhang, Mingjie Zhang, Zheng Zhao, Changhai Luo, Haikui Tong

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The Shaliuhe chromite body, situated in the Northern Margin of the Qaidam Basin (northeastern Qinghai-Tibet Plateau), is a newly discovered podiform chromitite hosted in an ophiolitic sequence, which provides an important basis for chromite exploration in the northeastern Tibetan Plateau. This study analyzed the mineral chemistry of chromite and the whole-rock major and trace element compositions of the ophiolite to investigate the genesis of the chromite, the composition of the parental magma, and the tectonic setting. The results are as follows: The chromite in the Shaliuhe ophiolite can be divided into primarily magmatic origin with some hydrothermal modification, and is generally of high-Cr type with a Cr# (chromium number) ranging from 61.74 to 99.74 (average 85.67). The chromite has a low TiO2 content (0.04–0.29 %), which is consistent with the typical geochemical characteristics of ophiolite-hosted chromitite. The chromite formed in a forearc tectonic setting of a subduction zone with a specific "magma-dominated + fluid-reworked" genetic mechanism: In the early stage, boninitic melts interacted with mantle peridotite through melt-rock reaction and melt mixing, promoting Cr saturation and crystallization to form primary chromite. In the late stage, serpentinization fluids dissolved and reworked the primary chromite, and the metasomatism by subduction-related slab fluids/melts influenced the final morphology and local re-enrichment of chromite. The parental magma exhibits a boninitic affinity and was derived from a highly depleted forearc mantle. The Shaliuhe ophiolite belongs to the SSZ (supra-subduction zone) type. The mantle source was dominated by forearc mantle peridotite, which underwent a high-degree partial melting process (exceeding 25%). This study provides a regional case for understanding the genesis of ophiolite-hosted podiform chromitite and offers a scientific basis for assessing the chromite resource potential in the North Qaidam Orogen.
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Polygenetic garnet records subduction, exhumation and anatexis of the Sulu orogenic belt

ZHANG Ruirui, LIU Zhong''ao, LI Yang, CAO Yuting, MENG Yuanku, LI Xuping, Wang Songjie

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Garnet, owing to its exceptional physicochemical stability and strong capacity to incorporate trace elements, is widely employed to constrain metamorphic conditions and interpret geological processes. However, during continental deep subduction and exhumation, garnet often exhibits complex compositional zoning and multi-stage growth or modification, complicating its geological interpretation. This study investigates phengite-rich gneisses and leucogranites from the Yangkou area of the Sulu orogenic belt, integrating inclusion petrography with major- and trace-element analyses of garnet. Four types of garnet with distinct genetic origins are identified: Grt I (gneiss core) formed during prograde to peak high-pressure–ultrahigh-pressure metamorphism; Grt II (gneiss mantle–rim) represents dissolution–reprecipitation induced by external melt infiltration during exhumation; Grt III (leucogranite core) records diffusive modification of captured metamorphic garnet by anatectic melt; and Grt IV (leucogranite mantle–rim) crystallized directly from the evolved granitic melt at a late magmatic stage. This sequence of four garnet generations systematically documents the evolution of the continental crust from subduction through exhumation to anatexis, highlighting the significant influence of melt–rock interaction on garnet chemistry. Combined zircon geochronology and calculated rare earth element (REE) partition coefficients reveal that peak-stage Grt I is significantly enriched in HREE relative to coexisting zircon, indicating that garnet may serve as the principal HREE reservoir under “dry” metamorphic conditions. In contrast, Grt IV and associated zircon display near-equilibrium partitioning or slight HREE enrichment in zircon, consistent with experimental observations from melt-bearing systems. These results elucidate the multi-stage evolution of garnet in the Sulu UHP rocks and provide new insights into melt activity, mineral competition, and element redistribution during deep continental subduction.
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Indicator Study of Garnet for Diamond Provenance in the Chenggang–Xinyi Area, Northern Jiangsu

CAI Yitao, ZHANG Qi, XIAO Bingjian, WANG Guoqiang, ZHOU Qizhong, ZHANG Xuan, ZHAO Yu, ZHANG Yingjie

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The Xinyi diamond placer is the only diamond-bearing placer deposit with proven resources in Jiangsu Province. However, the provenance of the diamonds and the exploration clues for potential primary deposits have long remained unresolved. In this study, systematic analyses of garnets from heavy mineral samples in the Chenggang–Xinyi area were conducted to trace the source region and to explore new indicators for primary diamond deposits. Bulk samples from the Xinyi placer (XK01, XK02, and XK03) and artificial heavy mineral concentrates from mafic–ultramafic rocks in the Chenggang Uplift were collected. Major-element compositions of the garnets were quantitatively analyzed using an electron microprobe, yielding 288 valid datasets. The results show that garnets from both the placer and the Chenggang Uplift are similar in composition, dominated by G3- and G4-type garnets, with occurrences of G3D-type garnets. The major-element compositions of garnets from the placer display a significant linear correlation with those from the Chenggang Uplift, indicating consistent elemental trends. This geochemical relationship suggests that the diamonds in the Xinyi placer were derived from metamorphosed pyroxenite within the Chenggang Uplift. Future exploration should therefore focus on identifying eclogite-type (E-type) indicator minerals. The garnets from the placer bulk samples mostly retain angular crystal shapes and resorption features, reflecting short-distance transport and implying that the diamonds were not transported over long distances but originated from local primary sources. These findings provide new mineralogical evidence for constraining the regional diamond metallogenic potential and guiding further exploration in northern Jiangsu.
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Three-dimensional shear wave velocity tomography of the upper crust in the Tongling ore concentration area

zhaorongtao, fengmei, anmeijian, yangyan, shidanian, liushasha, huangshi

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Located in the Middle-Lower Yangtze River Metallogenic Belt, Tongling represents a unique ore concentration area. The velocity structure of its shallow crust plays a crucial role in deciphering the Mesozoic metallogenic processes of the entire ore district and holds considerable value for deep mineral exploration. During 2022–2023, we deployed 57 temporary broadband stations with a minimum inter-station distance of 2-5 km in eastern Tongling. We apply the continuous records to derive a high-resolution three-dimensional shear-wave velocity structure of the upper-crust in the study region by ambient noise surface tomography. The results show that the S-wave velocity in the shallow part of Xuannan Sag is significantly lower than that of Tongling Uplift, and the boundary of S-wave velocity anomalies delineates well the occurrence of the Dingqiao–Daihui Fault, which dips southeastward and extends to a depth of ~3 km. The S-wave velocity below 1 km depth of the Tongling Uplift is higher (~3 km/s) than that of the Xuannan Sag, implying possible intrusions of large-scale granities in the Tongling uplift. These intrusions display a dome-like laccolith beneath the Xinqiao and Shizishan, and a sill-like bedrock in the southern Fenghuangshan region. The results are of great significance for understanding the metallogenic dynamic process of the Tongling ore concentration area, and also provide new evidence for the magmatic underplating model of the Middle-Lower Yangtze River Metallogenic Belt.
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Structural characteristics and evolution of a multi-phase rifting sag within a wide rift basin: A case study of the Chagan Sag, Yin’e Basin

Shan Shuaiqiang, Wang Debo, Fu Mao, Wang Bin, Wan Jing, Yang Yabo, Zhang Chenyu, Shen Bingbei

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The Yin"e Basin, located in the central-western part of Inner Mongolia Autonomous Region, consists of a series of Early Cretaceous rift depressions and forms part of the Late Mesozoic wide rift system in Northeast Asia. The Chagan Sag at the eastern margin of the basin is one of the few proven hydrocarbon-rich sags, whose Lower Cretaceous geological structure records the evolutionary process of multi-phase rifting. Conducting research on the geological structure and evolution of Chagan Sag is not only significant for revealing the evolution of Early Cretaceous intracontinental rift basins in northern China, but also provides valuable references for identifying hydrocarbon-rich sags and evaluating exploration targets in the region. Based on integrated datasets including 3D seismic surveys, drilling data, core samples, and field geological investigations, this study systematically investigates fault systems through structural analysis methods to characterize the grouping and evolutionary stages of major faults. The research identifies and delineates volcanic edifices to examine episodes of volcanic activity, reconstructs the Structural evolution since the Early Cretaceous using balanced cross-section techniques, and comprehensively analyzes the Early Cretaceous tectonic-sedimentary filling processes in the Chagan Depression. This study shows that the Chagan Sag exhibits well-developed volcanic-sedimentary interbeds, which can be vertically subdivided into three distinct structural layers: the rift structural layer, rift- depression transition structural layer, and depression structural layer. Within the rift sequence, three fault systems with NNW-, NNE-, and NE-trending orientations are identified, exhibiting an east-west zonation structural pattern. Three distinct episodes of volcanic activity are recognized in the Lower Cretaceous Suhongtu Formation, displaying a clear SE-to-NW migration trend throughout the sag. The results demonstrate that the Chagan Sag developed as a volcanically rift basin during the Early Cretaceous, having undergone a complete evolutionary sequence from rifting through rift-depression transition to depression since the Cretaceous. The rifting stage can be further subdivided into: (1) initial rifting phase, (2) intense rifting episode I, and (3) intense rifting episode II. Spatiotemporal variations in the activity of master faults were found to exert fundamental control on both the structural evolution of the sag and the migration patterns of volcanic activity.
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Origin, Evolution, and Geological Implications of the Mianyang - Changning Erosion Sag in the Sichuan Basin during the Late Sinian to Early Cambrian Epoch

Gao Jianguo, Li Shubing, Li Zhiwu, Meng Xianwu, Wang Haijun, Wang Dong, Wei Yan, Wang Ying, Bao Jiajie

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Abstract As hydrocarbon exploration continues to advance into deeper-buried and older marine deep- to ultra-deep strata, the discovery of the large-scale paleo-structure, the "Mianyang-Changning Sag," within the Sinian to Lower Cambrian strata of the Sichuan Basin has make remarkable breakthroughs and demonstrated considerable potential. This Sag exerts notable control over the sedimentation, reservoir development, and hydrocarbon accumulation in the Sinian-Cambrian strata of the basin. However, substantial controversies persist in the industry regarding its development timing, geological characteristics, evolutionary models, and genetic mechanisms, which to some extent constrain hydrocarbon exploration practices centered around this Sag. To address this, this study utilized the newly acquired 2D/3D seismic and drilling data, combined with field outcrop observations and experimental analyses, to investigate the Sag's distribution, genesis, evolution, and its relationship with hydrocarbon enrichment and accumulation. The results indicate: 1) The Mianyang-Changning Sag extends in a nearly north-south direction, featuring a "fine-necked" negative relief with "deeper in the north, shallower in the south, steeper on the eastern side, gentler on the western side, and north – south openings". 2) During the Tongwan Movement, multiple phases karst dissolution combined with fluvial erosion was the dominant factor in the formation of this Sag. Features such as stratigraphic unconformities (e.g., truncation at the top of the Dengying Formation and onlap at the base of the Maidiping and Qiongzhusi formations), the identification of erosional residual islands and hills (Penglai, Jintang, and Pengzhou) within the Sag, consistent lithology and facies belts of the member 1 of the Dengying Formation both inside and outside the Erosion Sag, and drilling phenomena such as lost circulation and blowouts all indicate that karst and fluvial processes controlled the Sag's development. Seismic data from the western side of the erosional sag reveal relatively continuous reflection events at the base of the Dengying Formation along the Sag boundary, indicating the absence of significant faults cutting through the Sinian and Cambrian strata at the Sag's steep slopes, further confirming that this Sag is a large-scale erosional feature; 3) Severe absence of the members 3 and 4 of the Dengying Formation within the Sag suggests that the Tongwan II episode was the main formation period for the Mianyang-Changning erosional sag, followed by a phase of adjustment and infilling. This Sag contains thick and high-quality source rocks, with well-developed reservoirs at the steep slopes, representing optimal spatial-temporal source-reservoir configurations. Therefore, this area can be regarded as a key exploration target for marine deep- to ultra-deep natural gas in the future.
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Physical simulation study on the development and evolution of fault systems under the coupled control of extension direction changes and basement fault activatio

Zhangyiyong, Huang lei, LiXin, LiWei, Wangshaohao, WangRuoWei, WangWei, Liuchiyang

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The study of extensional fault systems is crucial for deciphering the tectonic evolution of rift basins and revealing regional geodynamic mechanisms. Although physical simulations have demonstrated that stress orientation and basement fault activity are key factors controlling extensional structures, the three-dimensional evolutionary processes of fault systems under the coupled influence of multi-phase extension direction changes and basement fault reactivation remain insufficiently explored. This study employs a physical modeling platform to simulate the evolution of extensional fault systems under two-phase extension with varying directions, based on pre-defined basement faults. During the first-phase orthogonal extension, a fault zone consisting of long straight boundary faults perpendicular to the extension direction and internal short faults was formed, with a transition from soft to hard linkage observed at fault stepovers. In the second-phase oblique extension, pre-existing faults generated during the earlier orthogonal extension continued propagating upward as inherited cover faults, exhibiting a staged evolution: In the initial stage, fault reactivation dominated within the fault zone, characterized by reactivated faults of varying lengths and unchanged strikes; During the intermediate stage, fault strikes within the zone began to shift, accompanied by newly formed faults with heterogeneous orientations, resulting in more complex structural patterns and cross-cutting relationships; In the late stage, an increasing number of peripheral new faults emerged, displaying en-echelon arrangements orthogonal to the extension direction and sensitive to stress field variations. Furthermore, PIV technology precisely captured the spatial reactivation positions of secondary faults and the timing of new fault formation during oblique extension, revealing differential fault development and linkage mechanisms within the fault zone. The experiments demonstrate that the evolution of late-stage fault systems is jointly controlled by basement faults, pre-existing cover faults, and extension direction. Basement faults play a fundamental role in shaping the overall fault zone architecture, while the extension direction significantly influences the morphology and structural characteristics of faults both within and outside the zone. The simulation results align with natural deformation examples, providing a model and guidance for tectonic analysis in similar geological settings.
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Geochemical characteristics of the Xujiahe Formation in the Muchuan area of southwestern Sichuan Basin and its indicative significance for the paleoenvironment and tectonic background of the source region

liu jianqing, zhao zhan, feng weiming, lu junze, feng xinglei

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The material composition of clastic rocks is closely related to the tectonic background and paleoclimatic conditions of the source area. The study of sedimentary geochemistry can not only trace the tectonic environment of the source area during the sedimentary period, analyze paleoclimate and environmental conditions, but also enrich and improve the scientific system of sedimentary geochemistry. Research on this aspect of the Xujiahe Formation in the Muchuan area of southwestern Sichuan Basin has not yet been carried out. Based on profile measurement and microscopic research, geochemical studies of the Xujiahe Formation in Muchuan were carried out. Research shows that: (1) The Xujiahe Formation is mainly composed of debris sandstone, with a large amount of sub-volcanic debris, a small amount of metamorphic rocks (schist, calenite) and polycrystalline quartz. The chemical analysis of major elements shows that it is rich in quartz. The material sources come from passive continental margins, active continental margins and continental island arcs; (2) The sandstone and mudstone of the Xujiahe Formation is rich in light rare earths and has obvious negative Eu anomalies. The standardized curve shapes of the average mudstone are similar. The contents of Sr, Cu and Mo are lower than those of the average mudstone. The contents of Ga, V, U, Th, Cr, Co, Sc and Rb are close to those of the average mudstone. The contents of Ba, Ni and Zn are slightly higher than or close to those of the average mudstone. The elements Zr and Hf with terrestrial properties are significantly higher than those of the average mudstone. Geochemical characteristics show that it mainly comes from feldspar volcanic rocks, sedimentary rocks, granites and andesite; (3) The source area of the Xujiahe Formation suffered from moderate chemical weathering during sedimentation and was a warm and humid sedimentary environment. Evaporation and oxidation in the basin are relatively intense, and the water body has the characteristics of brackish water, with an ancient salinity ranging from 7.10‰ to 20.60‰. During the sedimentation process, the stratification of the water body was weak to moderate, and a reducing sedimentary environment occurred locally. The origin of the Xujiahe Formation is closely related to the convergence and rifting of the Kenorland, Columbia and Rodinia paleocontinents in southern China, as well as the early Paleozoic passive continental margin basin, the Caledonian collision orogeny, the Haixi-Indosic rifting cycle and the Late Triassic Paleo-Tethys Ocean closure collision orogeny. It is a sedimentary material for the re-cycle orogenic belt. And mainly they are long-distance sources in South China, with a small amount being close-range sources in the Kangding – Yunnan Paleocontinent. The source rock type is the silicon-aluminum layer of the upper crust and they are similar; The semi-arid and oxidizing paleoclimate environment within the basin is related to the surrounding closed paleoctopographic conditions, poor air circulation and strong evaporation.
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Early Paleozoic Post-Orogenic Extension in the Northern Altun Tagh: Constraints from Geochronology and Geochemistry of Diabase Dykes

FU Shunhao, YANG Mingcan, DAI Lingqi, YE Xiantao

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The North Altun Orogenic Belt, a key part of the Qinling-Qilian-Kunlun orogenic system, preserves critical records of the evolution of the Proto-Tethys Ocean. However, the timing of its tectonic transition from post-collisional compression to extension remains poorly constrained. This study presents detailed field investigations, zircon SIMS U-Pb dating, and whole-rock geochemical and Sr-Nd isotopic analyses of newly identified diabase dikes in the Kaladawan and Aktash areas in the North Altun terrane. Zircon U-Pb dating reveals that the diabases emplaced at ca. 441 Ma. The rocks are classified as tholeiitic basalts, exhibiting low MgO (4.07%~4.47%) and total alkali (Na2O+K2O=4.84%~5.82%) contents with relatively high Fe2O3T (16.18%~16.75%). They are enriched in light rare earth elements (LREE) and large-ion lithophile elements (LILE) but depleted in high-field-strength elements(HFSE), displaying pronounced negative Nb-Ta-Zr-Hf-Ti anomalies on primitive mantle-normalized spider diagrams. Furthermore, their high initial 87Sr/86Sr ratios (0.7117~0.7125) and extremely low εNd(t) values (?20.0~?19.8) indicate derivation from an ancient lithospheric mantle which metasomatized by fluids released from subduction slab. These findings suggest that the diabases are direct products of post-orogenic extension, thus constraining the timing of the tectonic regime from compression to extension in the North Altun Orogenic Belt occurred at ca. 441 Ma.
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Geochemical Characteristics of Guidong Pluton in Eastern Guangdong and Their Constraints on the Formation of Ion-adsorption Rare Earth Deposits

guo min, tan juan juan, wang lei, tong Xirun, HUANG Huagu, XIAO Xilian, WANG Jietao, SHAO Xin, qiu xiao fei

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The enrichment mechanism of rare earth elements in ion-adsorption rare earth deposits is a hot topic in ore deposit studies. Comprehensive zircon U-Pb geochronology and whole-rock major and trace element analyses were carried out on the fresh granites from 3 drill hole in the ion-adsorption rare earth deposit of the Guidong pluton in Shaoguan, northern Guangdong. The granites are mainly composed of quartz, potash feldspar, plagioclase and biotite, and are mainly of monzogranite and syenogranite in lithology. Zircon U-Pb dating of two monzogranites and one syenogranite show that their formation ages are 160±1 Ma, 162±1 Ma and 160±2 Ma, respectively, indicating that the western part of the Guidong pluton is formed concentrated at the Early Yanshanian (~160 Ma). These granites are peraluminous to strongly peraluminous, with high alkali content. The syenogranite is highly fractionated, featured by high SiO2 content, low Zr/Hf ratio, and enrichment of K and Rb. It is suggested that the Guidong Yanshanian granites are aluminous A-type granite, which may be derived from the biotite dehydration partial melting of late Paleoproterozoic tonalite under anhydrous conditions, and the syenogranites are the product of intense fractional crystallization of monzogranites. Compared with the adjacent Dadaonshan granites, it is proposed that the intense fractional crystallization of alkaline felsic melts may play an important role for the formation of HREE-enriched ion-adsorption rare earth deposits.
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Fractionation and Accumulation of Rare Earth Elements during in Zhaibei Rare Earth Deposits in Jiangxi,China

Yang Pengtao, Hong Hanlie, Zhao Chenlei, Yin Ke, Zhao Lulu, Liu Chen, Ji Kaipeng, Jia Fuwen

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The weathering crust-type rare earth deposits occur widely in South China, but understanding of mechanisms of differentiation and enrichment of rare earth elements (REEs) during weathering process is still very limited. In this study, X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) methods were employed to better characterize the presence of REEs in the Zhaibbei rare earth deposit in southern Jiangxi Province. Our results showed that the Zhaibbei weathering profile of the rare earth deposit preserved the complete in-situ weathering soil layers, including saprolite layer, illuvial layer, eluvial layer, and topsoil layer from the bottom to the top. The saprolite layer contains mainly illite, smectite, and kaolinite. The illuvial layer and eluvial layer have similar clay mineral compositions of dominantly halloysite, kaolinite, and illite, with minor vermiculite, and the topsoil layer is consisted of mainly halloysite, with minor kaolinite and vermiculite. The heavy rare earth elements (HREEs) in the weathering profile are mainly associated with iron oxide minerals and are enriched in iron oxide minerals through substitution and co-precipitation, while the light rare earth elements (LREEs) are mainly associated with halloysite and kaolinite in ion adsorption. In addition, REEs in the upper profile can also form discrete secondary rare earth phosphate minerals. The enrichment and differentiation of REEs during the weathering process are mainly related to clay minerals and hematite. This study reveals occurrence of ore-forming REEs in the weathering crust-type rare earth deposit from the view of direct microscopic observation, which provides key evidence for the differentiation and enrichment process of REEs in rare earth deposits in the South China weathering crust.
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Metallogenic mechanism of ion-adsorbed rare earth deposit in Xiayao, Jiangxi Province

li ruodan, liu xinxing, zhang juan, chen binfeng, huang gang, zhang zhiwei

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To restore the complete process of rare earth element enrichment during the formation of Ion-adsorption rare earth type deposits. In this study, the ore-forming parent rock and weathered crust samples in the Xiayao ion-adsorption rare earth type deposit were studied by inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma spectroscopy (ICP-OES), X-ray diffraction experiment (XRD), electron probe, zircon U-Pb dating and Hf isotope test. The Keshubei granite is identifiedas high-K calc-alkaline and slightly peraluminous. Zircon grains from the Keshubei granite exhibit U-Pb ages of 196.26±1.53 Ma, 194.72±1.1 Ma, and 197.18±1.77 Ma. The value of zircon εHf(t) inKeshubei graniterangefrom-3.35to1.79. Rare earth minerals include apatite, zircon, bastnaesite and Xenotime. The rare earth elements in the weathered crust are enriched in the middle and upper parts. It is indicated that the Keshubei granite is the product of Indosinian magmatic activity, which is produced in the ancient felsic crustal remelting environment induced by the extensional tectonic environment. The enrichment process of rare earth elements is mainly related to magmatic evolution, supplemented by hydrothermal action. The secondary enrichment of adsorbed elements in the weathered crust is restricted by clay minerals, pH value and weathering degree.
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Location prediction and exploration of VMS metallogenic system

WANG Jingbin, WANG Yuwang, XIE Hongjing, Li Qingzhe, GENG Jian

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The VMS (volcanic massive sulfide) deposits associated with marine volcanic activities, constitute a metallogenic spectrum which range from Cu type, Cu-Zn type, Cu-Pb-Zn type to Pb-Zn type. The deposits are significant sources of minerals such as copper, zinc, lead, silver, gold, and sulfur. Due to the high ore grade, diverse useful components, and high economic value, VMS deposits are a globally important target for mineral exploration. This paper systematically summarizes the classification, ore-forming environment, characteristics of the metallogenic system, and positioning prediction indicators of VMS deposits, proposing that VMS deposits are products of submarine volcanic hydrothermal systems in extensional tectonic settings and are related to marine sodium-rich volcanic rocks.
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Mantle source lithology of ocean island basalts from Réunion Island in the Southwest Indian Ocean

NIU Chen, WANG Xiaojun, ZHAO Jian, LIU Jianqiang, ZHANG Chao, CHEN Lihui

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Upwelling mantle plumes can transport deep mantle materials into the shallow mantle. Therefore, identifying the lithological composition of mantle plumes in the shallow mantle is helpful for understanding the Earth's deep mantle compositions and the related geodynamic processes. Seismic tomography reveals that the root of the Réunion mantle plume is connected to the African large low-shear-velocity province in the lower mantle. This suggests that the Réunion mantle plume originates from the lower mantle. However, the lithological composition of this plume remains unclear. Ocean island basalts (OIBs) from Réunion Island were generated by partial melting of the Réunion mantle plume over the past two million years, making them ideal samples for investigating the lithological composition of the mantle plume. To explore the lithological composition of the Réunion mantle plume, this study presents whole-rock major element compositions of the Réunion OIBs, along with the chemical compositions of olivine phenocrysts within these basalts. We first estimated the primary magma compositions of the studied samples, which were found to be rich in MgO and TiO2 but deficient in SiO2, CaO, and Al2O3. When comparing the primary magma compositions with experimental melts of different mantle rocks, we found that they predominantly fall within the range of melts produced by melting of silica-deficient pyroxenite. To further evaluate this proposal, we analyzed the chemical compositions of olivine phenocrysts in the Réunion OIB samples. The results indicate that the Fo value of olivine phenocrysts ranges from 80.1 to 90.1. Notably, high-Fo olivine phenocrysts exhibit elevated Ni contents, reduced Ca and Mn contents, and high Fe/Mn ratios. These olivine compositions resemble those found in Loihi (Hawaii) OIBs, whose source contains silica-deficient pyroxenite, but they are distinctly different from olivine phenocrysts in equilibrium with peridotite-derived melts. This suggests a significant contribution of pyroxenites to the mantle source of Réunion OIBs. Therefore, both the whole-rock major elements and the compositions of olivine phenocrysts suggest that the mantle source lithology of Réunion OIBs primarily consists of silica-deficient pyroxenite. This indicates that the Réunion mantle plume contains pyroxenite components rather than being composed exclusively of peridotite.
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Geochemical and chronological characteristics of detrital rutile in the karst bauxite of China and its geological significance

Liang rongrong), Zhang Tongyi), Hu Zhaoguo), Zhang Baotao), Liu Sen), Liu Xuefei)

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Since the Paleozoic era, different tectonic plates around the world have formed abundant karst bauxite at different times, and their complex formation process not only contains rich climatic information, but also records important geological events such as plate tectonic evolution. Among them, detrital rutile is an important associated mineral in karst bauxite, with stable chemical properties that can record key tectonic events in geological history. Based on the trace element and U-Pb age data of rutile from 23 karst bauxite deposits in the North China Craton and South China Block of China , this study systematically explores its genetic types and coupling relationship with supercontinental evolution. The research results show that the genesis of rutile in karst bauxite of different ages in China is mainly metamorphic, but the formation conditions are different. The metamorphic temperature of rutile in the Late Carboniferous bauxite of the North China Craton is relatively high, mainly granulite facies, while the metamorphic temperature of rutile in the bauxite of different ages of South China Block is relatively low, between amphibolite and granulite facies. The Late Carboniferous bauxite in the North China Craton records extensive and abundant metamorphic rutile from the aggregation period of the Nuna supercontinent, revealing that the North China Craton was widely involved in the aggregation activities of this supercontinent, and the metamorphic rocks formed at the same time laid the material basis for the formation of Carboniferous bauxite deposits. The rutile formed during the disintegration of the Rodinia supercontinent and the assembly of the Gondwana supercontinent is generally recorded in bauxite of different periods in the South China Block, which indicates that the South China Block deeply participated in the evolution of the supercontinent in these two stages, and the metamorphic rocks formed provided important materials for the formation of bauxite in different periods of the South China Block. This study reveals that detrital rutile in bauxite can not only trace the source rocks of bauxite but also contain rich information on plate tectonic evolution, providing a new perspective for exploring global tectonic evolution.
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Origins of ore?forming materials and enrichment mechanisms of the Guoluolongwa gold deposit, Eastern Kunlun Orogenic Belt, China

Zhang Xinming, Zhang Libin, Li Wenjun, Wei Junhao, Chen Jiajie

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The Guoluolongwa gold deposit, located in the Gouli district of the Eastern Kunlun Orogenic Belt, exemplifies a Late Devonian-Early Carboniferous post?collisional extensional magmatic?hydrothermal vein?type gold system. We employed comprehensive field mapping, backscattered electron imaging (BSE), TESCAN mineral analysis (TIMA), in situ LA?ICP?MS trace element profiling, and LA?MC?ICP?MS sulfur isotope microanalysis to unravel its ore genesis. Four paragenetic stages were delineated—Stage I (quartz-pyrite), Stage II (quartz-arsenopyrite–pyrite), Stage III (quartz-polymetallic sulfides), and Stage IV (calcite-quartz)—and three pyrite generations (Py1-Py3) were identified. Progressive variations in trace element concentrations (Co, Ni, As, Au) and Co/Ni ratios among pyrite generations confirm a dominantly magmatic?hydrothermal fluid source. Pyrite δ34S values decline from 3.77‰ to 5.95‰ in Py1 to -2.60‰ to 0.06‰ in Py3, reflecting incremental oxidation and meteoric water infiltration that lowered H?S activity and drove sequential sulfide and gold precipitation. Integrating Re-Os ages (375~354 Ma) and Pb-H-O isotopic data, we propose a genetic model whereby magmatic?hydrothermal fluids migrated along EW?trending faults and precipitated in structural conduits during post?collisional extension.
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Sedimentary Environment and Material Source of the Hanjiashan Manganese Deposit in the Mianxian-Lueyang-Ningqiang Area, Shaanxi ProvinceGAO Feng1,2,CAI Wenchun1,2*,PAN Liang1,2,ZHANG Xiaoming1,2,KANG Qinqin2,3

GAO Feng, CAI Wenchun, Cai Wenchun, ZHANG Xiaoming, KANG Qinqin

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The Mianxian-Lueyang-Ningqiang area is a significant polymetallic ore concentration region in the Southern Qinling Mountains and one of the main production areas for Sinian manganese deposits in Shaanxi Province, China. This study focuses on the Hanjiashan manganese deposit located in the central segment of the Mianxian-Lueyang suture zone. Through systematic field geological investigations, combined with petrographic, mineralogical, geochemical, and C-O isotopic analyses, the genesis, sedimentary environment, and material sources of the manganese deposit are discussed. The results indicate that the manganese-bearing series belongs to a carbonaceous fine-clastic rock - magnesium carbonate rock formation in the upper member of the Lower Sinian Doushantuo Formation, with the ore bodies occurring as stratiform and lenticular forms. Manganese deposits primarily during the sedimentary-diagenetic stage and are predominantly compsosed of rhodochrosite, manganoan dolomite and rhodochrosite, with observed framboidal pyrite. Geochemical characteristics show that the ores have low average ratios of Fe/Mn (0.10), Co/Ni (0.37), V/(V+Ni) (0.69), and Al/(Al+Fe+Mn) (0.11), but high average ratios of V/Cr (3.42), U/Th (1.17), and Y/Ho (34.47). The Post-Archean Australian Shale (PAAS)-normalized rare earth element (REE) patterns exhibit a left-leaning trend with a significant positive Y anomaly, and weak positive anomalies for both Eu (avg. 1.24) and Ce (avg. 1.33). The average δ13CPDB value is -5.46‰, which is close to values characteristic of modern seafloor hydrothermal vents and magmatic sources. Synthesizing these findings, it is concluded that the manganese deposit formed in a suboxic-to-anoxic outer shelf environment, with relatively high mineralization temperatures (avg. 106.07℃) and low salinity (avg. 1.88‰). The ore-forming materials were primarily derived from a submarine hydrothermal system, with additional contributions from seawater, classifying it as a hydrothermal sedimentary-type manganese deposit. This study confirms the dominant role of hydrothermal sedimentation in the mineralization process, deepens the understanding of manganese deposit genesis in the Mianxian-Lueyang-Ningqiang area, and provides a theoretical basis for research on regional metallogeny and prospecting exploration for manganese deposits.
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Lianyunshan - Hengyang fault zone in Hunan Province: structural attributes, formation background, and dynamic mechanisms

Bai Daoyuan, Zeng Guangqian, Hang chao, Li Bin, Chen Jianfeng, Xao Liquan

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The Lianyunshan-Hengyang fault is a typical representative of regional NE-trending deep major faults, extending for 430 km within Hunan Province. Along this fault, numerous mineral deposits and large-scale fault basins have developed, rendering it highly significant in terms of resources and economic value. However, research on its overall vertical and lateral structural composition, the temporal context of its formation, and its dynamic mechanisms remains limited. In light of this, this paper conducts a comprehensive study of the fault"s structural composition, tectonic attributes, formation age, and dynamic mechanisms through field structural investigations and analysis of existing regional geological and geophysical data. The results indicate that the Lianyunshan-Hengyang fault is a composite structural zone composed of numerous faults of varying orders, scales, attitudes, ages, and properties and fault basins from deep to shallow levels. Geophysical exploration data, including regional gravity, aeromagnetic, seismic, and geothermal data, reveal the presence of a continuously extending large fault zone at depth along the Lianyunshan-Hengyang fault. At the surface, the Lianyunshan-Hengyang fault manifests as a large-scale fault zone, 10–25 km wide, consisting of a NE-trending main fault, Cretaceous-Paleogene fault basins on the northwestern side (hanging wall) of the main fault, and secondary basin-controlling faults with various strikes within and along the basin margins. The NE-trending main fault is composed of five NE-trending faults that are offset end-to-end from northeast to southwest, along with connecting faults oriented NEE and SN. The faults within the zone can be classified into six types based on strike: NE, NNE, SN, NW, EW, and NEE. These faults primarily formed as thrust and strike-slip faults under early Indosinian NW-compression, late Indosinian SN-compression, and early Yanshanian NWW-compression, and controlled the development of fault basins during the Cretaceous extensional activity. Under the NW–SE extensional environment of the Cretaceous, the various NE-trending main faults and connecting faults underwent inherited extensional activity, forming a continuous NE-trending large surface fault and an extended fault basin, thereby giving rise to the Lianyunshan-Hengyang deep major fault. The primary dynamic mechanism for regional extension is the circular mantle flow induced by the retreat of the ancient Pacific subducting slab. Mantle upwelling and horizontal flow of asthenospheric material associated with this mantle flow led to lithospheric extension and thinning.
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Developmental Characteristics of NW-Trending Blind Faults in the Pearl River Mouth Basin and Their Petroleum Geological Significance

Peng Guangrong, Li Hongbo, Wu Zhe, Cai Song, Zhu Dingwei, Zhang Huimin, Luo Junsheng, Hu Juncheng, Wan Zhifeng

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The Pearl River Mouth Basin is a significant petroliferous basin formed on a pre-Cenozoic complex folded basement at the continental margin of South China. Although previous studies have extensively investigated the structural characteristics and hydrocarbon accumulation in the basin, considerable controversy remains regarding the structural attributes and basin-controlling mechanisms of the NW-trending blind basement faults. Based on integrated gravity-magnetic data, well-seismic data, and field geological surveys in South China, this study employs a land-sea collaborative research approach to systematically identify and define three major NW-trending blind fault zones in the Pearl River Mouth Basin (Guigang–Yangjiang–Yitong, Huaiji–Huizhou–Beiweitan, and Lianzhou–Lufeng–Dongsha fault zones) and establish their geometric developmental models. The research indicates that: (1) The NW-trending blind fault zones exhibit distinct spatial distribution patterns. Onshore, they are characterized by fault zones, stratigraphic dislocation, and large-scale drainage systems, while offshore, they show strong correlations with gravity-magnetic anomalies, basement lithology, sag structural features, and high CO2 concentration distributions. (2) The activity of the blind faults can be divided into three main stages: formation (Indosinian movement), transformation (Yanshanian movement), and reactivation (Himalayan movement). (3) Based on the degree of control exerted by the blind faults on sag evolution, three differential evolutionary models of sags are established: multi-fault joint control (transcurrent-composite transtension), single-fault strong control (restricted transtension), and weak-fault extension control (segmented transtension). (4) The control of NW-trending blind fault zones on sag evolution and source rock distribution significantly influences hydrocarbon migration, accumulation, and resource potential. The exploration discovery of the Huizhou 19-6 oilfield confirms the important controlling role of NW-trending fault zones in hydrocarbon enrichment. In summary, this study systematically reveals for the first time the developmental characteristics and evolutionary history of the NW-trending blind fault zones in the Pearl River Mouth Basin, further deepening the understanding of the basin’s tectonic evolution and providing important guidance and reference for petroleum exploration in the northern South China Sea.
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Geochemistry of the Mesozoic alkaline magmatic rocks in Luxi, western Yunnan: Implication for the rifting evolution of the Gaoligong Tectonic Belt

Ren Yufeng

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Luxi ophiolitic mélange zone, situated along the Lushui-Longling-Ruili Fault in the southeastern margin of the Gaoligong Tectonic Belt between the Tengchong and Baoshan terranes in western Yunnan, has been debated on its origin, with models suggesting subduction and accretion from the Meso-Tethys Ocean or rifting induced by continental lithospheric thinning. Identifying the characteristics of mafic magmatic rocks within the mélange zone is crucial to resolving this debate. Through large-scale mapping, we discovered a series of alkaline magmatic rocks including lamprophyres, amphibole-bearing basalts, and TiO2-rich basalts in the Late Triassic to Early Jurassic turbidites. This study employs mineralogical, petrogenetic, and geochemical methods to investigate their genesis and tectonic background. The lamprophyres are classified as sannaites, and have a porphyritic texture and amygdaloidal structure with the phenocrysts of kaersutite, Ti-augite, and Ti-biotite, and matrix of cryptocrystalline potassium feldspar and minor albite. Geochemically, they belong to potassic alkaline lamprophyres, with K2O/Na2O ratios of 1.6 to 3.3 and Mg# values of 50 to 56, and their trace and rare earth element characteristics are similar to those of OIB, but their K, Ba, Sr, Nb, Ta and light rare earth elements are more enriched than those of OIB. Compared to the primitive mantle, the lamprophyres show low Mg# values, depleted Co, Cr, and Ni, with a negative Pb anomaly and without Eu and Ce anomalies, which suggest their magmas underwent the fractional crystallization of olivine and pyroxene, but did not experience the fractional crystallization of plagioclase, and did not suffer crustal contamination and alteration subsequently. The lamprophyres characterized by low εNd(t) (+3.57~+3.73), high 87Sr/86Sri (0.706027~0.706161), high (La/Yb)N (27.8~28) and Dy/Yb (2.6~2.7) suggest they originated from weakly depleted mantle regions, bearing phlogopite and amphibole and within the garnet-bearing lithosphere-asthenosphere boundary. The Ti-rich basalts are alkaline, and resemble the lamprophyres in trace element characteristics and Nd(t) values, but they lack hydrous minerals of amphibole and biotite. The amphibole-bearing basalts lie between the lamprophyres and Ti-rich basalts in mineral assemblage, containing TiO2-rich amphibole and biotite as well as plagioclase phenocrysts. In comparison with the regional mafic magmatic rocks, we conclude that these alkaline mafic magmatic rocks are probably formed during the Jurassic period, and are attributed closely to the asthenospheric convection generated by the Paleo-Tethys Ocean subduction that caused thinning and rifting of the Luxi lithosphere. This study demonstrates that the Luxi ophiolitic mélange is a rifting complex. These findings provide significant constraints for understanding the tectonic evolution of the southeastern Qinghai-Tibet Plateau during the Mesozoic era.
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Late Paleozoic continental arc magmatic flare-up and its driving mechanism in the Nuoergong-Langshan tectonic belt on the northern margin of the Alxa block

Yan Zhangqing, Tian Rongsong, Shi Chunhua, Fu Yong

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Late Paleozoic continental arc magmatic flare-ups in the northern margin of the Alxa Block records the key subduction to final closure processes of the Paleo-Asian Ocean (PAO) in the middle segments of the southern Central Asian Orogenic Belt (CAOB). However, the driving mechanism of the episodic continental arc magmatism is still unclear, which hinders a comprehensive understanding of the Late Paleozoic tectonic evolution process on the northern margin of the Alxa Block. In this study, detailed zircon U-Pb ages together with published data reveal the episodic continental arc magmatism in the Nuoergong-Langshan Belt (NLB) during the Late Paleozoic period, with Carboniferous (340～320 Ma) and Early Middle Permian (285～265 Ma) two main magmatic flare-ups and interval magmatic lull (320～285 Ma). The regional unconformity of sedimentary records, structural deformation, and metamorphic events supports a strong crustal shortening and thickening process consistent with the magmatic flare-ups. Quantitative geochemical analysis also revealed that the crustal thickness of the NLB during the early to middle Permian period was between 50～60 km, indicating a significant crustal thickening process. The magmatic lull of continental arc magmatism shows more depleted zircon Hf isotope compositions and younger two-stage model ages compared to the magmatic flare-ups, revealing the involvement of more mantle components. Therefore, the Late Paleozoic episodic arc magmatism in the NLB is related to the thickening of the continental arc crust driven by the process of subduction and tectonic coupling in the PAO.
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The major and trace elements of titanite indicate the magmatic-hydrothermal evolution of Suzhou A-type granite

pan wei, huqinghai, wuhui, wangwei, sunbinbin, liuxuemin, chenruo, wangxueqiu

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The Suzhou granitic pluton is the first identified Nb–Ta-rich granite in China. Elucidating its magmatic-hydrothermal evolutionary process is critical for advancing our understanding of petrogenetic processes and Nb-Ta mineralization mechanisms in the region. This study for the first time systematically conducts petrographic, geochemical and chronological studies on titanite in the amphibole- and biotite-bearing granite within the Suzhou pluton. Based on the mineralogical and geochemical characteristics of titanite, the magmatic-hydrothermal evolution sequence and its constraints on Nb-Ta mineralization are clarified. The titanite in Suzhou granite records both magmatic and hydrothermal evolution: (a) Magmatic titanite exhibits relatively homogeneous compositional zoning, with high LREE (mean: 16,355 ppm) and HFSE contents (e.g., Nb averaging 5,550 ppm), elevated high TiO? content, Th/U ratios, crystallization temperatures (680 ± 30°C), as well as lower CaO content and Lu/Hf ratios. (b) Hydrothermal titanite is primarily divided into two stages. Early-stage hydrothermal titanite formed in a high-fO? hydrothermal environment, characterized by low LREE (mean: 661 ppm) and HFSE contents (e.g., Nb averaging 880 ppm). In contrast, late-stage secondary hydrothermal titanite crystallized in a relatively reduced hydrothermal fluids, with geochemical features showing significantly enriched Nb content, reaching up to 8,796 ppm. LA-ICP-MS dating yielded U–Pb ages of 125.2 ± 7.2 Ma for magmatic titanite and 125.4 ± 2.8 Ma for hydrothermal titanite, indicating their collective formation within the Early Cretaceous granitic magmatic-hydrothermal system. During hydrothermal fluid evolution, the interaction of F-rich fluids with titanite, amphibole, and biotite triggered non-equilibrium dissolution, releasing substantial HFSEs (e.g., Nb, Ta) and REEs into hydrothermal fluid. These elements were subsequently remobilized by F-enriched, relatively reduced hydrothermal fluids, either precipitated as secondary hydrothermal titanite (depleted in LREE with exceptionally high Nb concentrations up to 8,796 ppm) and ilmenite around primary minerals, or migrated over short distances to form Nb-Ta-enriched minerals such as fergusonite-(Y) and samarskite-(Y). In short, titanite exhibits progressive depletion in REE and HFSE (e.g., Nb, Ta) as the granitic system evolves from magmatic to hydrothermal regimes, and F-driven metasomatism (e.g., biotite alteration) promotes Nb enrichment. This indicates that the compositional evolution (major and trace elements) and microtextural features of titanite effectively archive both magmatic and subsequent hydrothermal processes. Consequently, titanite emerges as a new indicator for tracing Nb-Ta mineralization in granitic systems.
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Geochronology and geochemistry of Early Paleozoic metamorphic rocks in the North Wulan terrane of the North Qaidam Orogen, and its geological significance

ZHOU Kai, GAO Yijie, KONG Huilei, ZHANG Jiangwei, ZHAO Min, JIN Delong, HE Yongkang, XIE Chunlin

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The North Wulan terrane representing the overriding plate of the Early Paleozoic subduction-collision system of North Qaidam Orogen, is key to understanding the composition of the lower part of the crust beneath arc?back-arc and the tectonic evolution of the subduction process of the South Qilian Proto-Tethyan oceanic crust. In this paper, we present detailed petrology, geochronology, geochemistry and metamorphic P?T condition of the representative mafic to felsic metamorphic rocks in the North Wulan Terrane. The results reveal that the protolith age and tectonic setting of the three types of metamorphic rock studied are significantly different. The amphibolites exhibit compositional characteristics similar to E-MORB, but it does not retain information about the protolith age and thus cannot be further discussed in terms of its significance. The biotite-amphibole gneisses display geochemical signatures of continental arc, with protoliths formed at 471 ± 3 Ma, representing magmatic records of the continental marginal arc during the subduction of the Proto-Tethyan oceanic crust. The granitic mylonites exhibit geochemical feature resembling arc granite and formed at 965 ± 6 Ma, which means that they represent arc magmatism in an active continental margin setting related to the assembly of the Neoproterozoic supercontinent Rodinia. Combined with previous studies, it is proposed that the composition of the lower part of the crust beneath arc?back-arc, represented by the North Wulan Terrane, are primarily composed of Precambrian basement (including various types and ages of metasedimentary and meta-igneous rocks) and Early Paleozoic continental arc magmatic rocks. These rocks were widely subjected to Middle-Late Ordovician HT/LP metamorphism, with the corresponding metamorphic ages concentrated around ca. 475–440 Ma. This period is notably confined to the late stage of oceanic subduction, as recorded by arc magmatism (ca. 510–450 Ma), and is nearly synchronous with the eclogite-facies metamorphic ages associated with subduction of oceanic crust documented in the Dulan UHP unit. Integrating previous studies on metamorphic P?T evolution, we suggest that the HT/LP metamorphism occurring under an extensional environment of the continental marginal arc during the late stage of plate convergence is caused by slab rollback. This highlights the critical role of studying metamorphism of the overriding plate of subduction zones for reconstructing the tectonic evolution of subduction of oceanic crust.
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Discovery of Diamonds in Mantle Peridotites from the Yushigou Ophiolite, North Qilian Orogenic Belt

ZHANG Manli, LIU Fei, FENG Guangying, ZHU Xinyang, FANG Zijian, wushaofeng, XU Jiahong, YANG Jingsui

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Ophiolite-hosted diamonds have been discovered in several ophiolites within the Neo-Tethyan tectonic belt, however, the presence of diamonds in Paleo-Tethyan ophiolites remains unclear. This study focuses on the 550~495 Ma Yushigou ophiolite within the North Qilian orogenic belt. Heavy mineral separation and petrological studies of mantle peridotites were conducted. The results reveal the separation of 25 diamond-grains and other unusual minerals from approximately 510 kg of harzburgite. The diamonds mainly range in size from 50 to 150 μm, exhibiting colorless to pale yellow hues, and display crystal forms including octahedral, broken irregular, and rounded shapes. Raman spectroscopy shows a characteristic peak at 1330.37 cm?1. The host harzburgite consists mainly of olivine (75%~85%), orthopyroxene (14%~24%), and minor chromian spinel (<1%). Olivine has Fo values of 90.9~93.23, classifying it as forsterite, with the highest Fo value (93.23) observed in olivine inclusions within chromian spinel. Orthopyroxene occurs primarily in two types of porphyroclastic and intergranular. Porphyroclastic orthopyroxene has Mg# values of 91.07~92.59, Al?O? contents of 0.94~1.92%, and Cr?O? contents of 0.43~0.73%. Intergranular orthopyroxene has Mg# values of 91.40~92.31, Al?O? contents of 1.09%~1.80%, and Cr?O? contents of 0.46%~0.65%. The variation ranges of Mg#, Al?O?, and Cr?O? in porphyroclastic orthopyroxene are all slightly larger than those in intergranular orthopyroxene. Chromian spinel has Cr# values of 56.14~70.21, Mg# values of 43.89~58.33, and TiO? contents below 0.05%. The Mg#-Cr# diagram of spinel indicates that the harzburgite underwent a high degree of partial melting (25%~35%) and experienced metasomatism by melts/fluids in a forearc subduction zone. Ultrahigh-pressure minerals like diamonds suggest formation depths >150 km. This implies that oceanic crust/mantle materials were transported into the deep mantle during subduction. Diamonds and other minerals formed under high-pressure and highly reducing conditions, were encapsulated by mantle peridotite and chromitite, and then were subsequently carried to the surface during the exhumation process. This study confirms the globally significant distribution of ophiolite-hosted diamonds and provides new insights into deep subduction processes and deep mantle material recycling within the North Qilian orogenic belt.
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Analysis of secondary surface deformation characteristics and formation mechanisms on the eastern shore of Dingmu co triggered by the 2025 Tingri Mw7.1 earthquake

Wu Kungang, Li Haibing, Pan Jiawei, Yang Shaohua, Liu Fucai, Zhang Siqi, Su Qiang, Marie-Luce Chevalier, Lu Haijian

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On January 7, 2025, at 09:05, an Mw 7.1 earthquake occurred in Tingri County, Xigaze, Tibet. The China Earthquake Networks Center (CENC) located the epicenter at 28.50°N, 87.45°E near Cogo Township, with a focal depth of 10 km. Field investigations identified the seismogenic structure as the Dingmuco Fault, the southern segment of the Xainza-Dinggye rift in the southern Tibetan Plateau. The earthquake produced a ~35km co-seismic surface rupture and caused secondary surface deformation along the eastern shore of Dingmuco, extending ~12km with a width varying between 0.2 and 0.5 km. A series of extensional (tension cracks, half-grabens, grabens) and compressional structures (sporadically distributed sand liquefaction features, pressure ridges, compressional bulges, and fold scarps), all parallel to the lakeshore and nearly N-S trending, develop progressively from east to west. These structures formed mainly within the poorly consolidated sandy sediments of the mid-to-lower sections of the alluvial fan. Detailed structural analysis reveals that the observed extensional features (e.g., tension cracks and grabens) and compressional features (e.g., compressional ridges and bulges) are not direct products of co-seismic rupture, but rather represent structures resulting from secondary shallow surface collapses induced by the earthquake. This phenomenon results from liquefaction, shear instability, and gravity-driven deformation of loose sediments under seismic loading. The dynamic formation process can be divided into four stages: liquefaction triggered by earthquake, initial instability, sliding deformation, and fluid migration facilitation. These stages collectively demonstrate a typical multi-stage coupling mechanism. During this seismic event, numerous buildings in villages such as Qiangga—located atop the slump mass—collapsed extensively. This destruction likely relates not only to seismic shaking effects in the hanging wall but is also closely associated with vibrations induced by the contemporaneous slumping deformation. Investigating such phenomena holds significant implications for both paleoseismic identification and geohazard assessment.
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Optimization Methodology for Calculating Carbon Sequestration Capacity in Core-Scale Basalt-CO₂ Mineralization Storage Based on Laboratory Injection Experiments

Zhou Yuantao, Li Bo, Zhang Fengshou, Shi Zhenming, Kong Deheng

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Basalt-CO2 mineralization sequestration is an emerging CCUS (Carbon Capture, Utilization, and Storage) technology for achieving China's ‘dual carbon’ strategy, among which the accurate evaluation of the sequestration potential of basalt formations is a key technical indicator for measuring the feasibility of mineralization sequestration projects. Currently, there are various methods for calculating the mineralization sequestration potential of basalt, such as the mineral replacement method and the unit mineralization method, but there is still a lack of consensus in the industry regarding the calculation principles, accuracy, and applicable conditions of different methods. Based on the independently developed CO2 steady-state seepage test system, this study conducted injectability mineralization tests to investigate the dynamic change processes of indicators such as solution ion concentration, permeability, and secondary mineral growth quality of basalt samples with different pore and fracture characteristics in the Wenchang area of Hainan during the long-term mineralization sequestration process, and by comparing the calculated values, the error ranges and principles of various calculation methods were clarified; on this basis, an optimized calculation method for carbon sequestration capacity was proposed and applied to calculate the carbon sequestration capacity of basalt formations in Heishanling (HSL), Penglai Town, Wenchang City, Hainan, and Bailonggang-Sanjia Port Area (SJG), Shanghai. The results show that: mineral dissolution mainly occurs in the early stage of the mineralization reaction, the concentrations of Ca2+ and Mg2+ ions are in a supersaturated state, and the permeability increases slightly followed by a continuous decrease; the growth of secondary minerals shows obvious regional characteristics, with dissolution reactions dominating in the inlet section and precipitation dominating in the outlet section, and simultaneously, affected by the pressure dissolution effect, the opening of fractured basalt decreased by 5.23 % and 2.97 % respectively during the mineralization process, the mass percentage of C element on the surface of intact basalt after the reaction was 2.6 %, and the reduction in fracture opening and pore 'blockage' are the main reasons for the decrease in permeability; differences in pore/fracture structures directly affect the carbon sequestration potential of basalt, and the carbon sequestration potential of basalt with large pores and fractures is 135.7 % higher than that of intact basalt with small pores; a comparison between the theoretical calculated values and experimental values of basalt carbon sequestration potential shows that the calculation error of the mineral replacement method is the lowest at 2.4 %, while the calculation results of the unit mineralization method and the pore filling method are significantly overestimated, and the optimized calculation method for carbon sequestration potential can improve calculation accuracy without introducing additional empirical parameters; using the optimized method, the potential carbon sequestration capacities of the proven basalt formations at the two sites (HSL and SJG) were calculated to be 7.01×104 tons and 9.50×104 tons under the condition of a 7500 m2 site, respectively. The above research results can provide a basis for the feasibility analysis of subsequent mineralization sequestration projects.
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The geochemical characteristics and genesis of Cryogenian Jiangkou banded iron formation, Hunan province

huangyuanhui, yangxiuqing, yehui, zhaochao, yangguowei, hezhiguo, zhangzimin, liushihan, Muhammad Ahmad

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Banded iron formations (BIFs) are common chemical sedimentary rocks in Precambrian strata. Neoproterozoic BIFs were mainly deposited at Cryogenian period (~717–635 Ma). Many scholars argued that the emergence of Neoproterozoic BIF is closely linked to the "Snowball Earth" event, but the causal relationship between them remains poorly understood. The Jiangkou BIF in the South China Block is a typical Neoproterozoic BIF. The Jiangkou iron ores are dominated by quartz, hematite and magnetite, followed by minor chlorite and carbonate minerals, which is characterized by the features of chemical sedimentary rocks. The studied BIF show high TFe2O3 and SiO2 contents, followed by Al2O3, CaO and MgO. Other elements, such as TiO2, MnO, Na2O, K2O, P2O5, high field strength elements and total rare earth elements (REE) are relatively low. Moreover, the Jiangkou BIF show significant positive correlations between Al?O? and TiO?, Zr, while there are moderate positive correlations between K?O and Al?O?, TiO?. All samples show low Y/Ho ratios (average of 29.2). When normalized to Post Archean Australian Shale (PAAS), all BIF samples show enrichment of high REE patterns relative to low REE patterns (LaPAAS/YbPAAS = 0.22~0.59) and positive Eu anomalies (Eu/Eu*=1.02~1.40). Comprehensively, we argued that iron was sourced from hydrothermal fluids and seawater. Furthermore, significant terrigenous clastic materials have been incorporated into Jiangkou BIF. The positve iron isotope values in Jiangkou BIF and the absence of significant negative Ce anomalies suggest that Jiangkou BIF was deposited in a suboxic to anoxic conditions. Combining with previous studies, we suggest that widespread anoxic and ferruginous oceans prevailed during the Cryogenian period. The oxygen released from meltwaters of localized glaciers could have triggered iron precipitation and leading to the formation of BIF.
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Genetic mechanism of the Tongkeng Ag-Zn polymetallic deposit in Dachang, Guangxi: Constraints from fluid inclusions and C-H-O-S-Pb isotopes

CHENG Yongsheng, LI Xiangyang, WANG Lei, OU Enguo, LI Xiangrui, WEI Honglian, WANG Songpu, ZENG Dexing, ZHANG Zewen, LI Yezheng

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The Dachang Tongkeng deposit in Guangxi is a world-class supergiant deposit, with long-standing research extensively elucidating its tin-polymetallic mineralization processes and enrichment mechanisms. In recent years, Ag-Zn polymetallic ore bodies have been discovered during mining development, yet studies on the genetic mechanism of this mineralization type remain extremely limited. This knowledge gap significantly constrains the comprehensive understanding of metallogenic processes in the Tongkeng deposit and hinders further exploration of polymetallic mineral resources. Focusing on the Ag-Zn mineralization, this study investigates the evolution of ore-forming fluids and material sources through fluid inclusion microthermometry, C-H-O-S-Pb isotope analyses, and field geological investigations, while exploring the genetic mechanism of Ag-Zn polymetallic mineralization and its intrinsic connections with other ore bodies.The homogenization temperatures of ore-forming fluids range from 102 to 321°C, with salinities of 1.2%–14.63% NaCleqv. Quartz H-O isotopes (δD=-59.8‰ to -57.9‰; δ₁₈^O_H₂_O=4.85‰~11.06‰) and calcite C-O isotopes (δ₁₃^C_V-PDB=-9.14‰~1.47‰; δ1?O_H₂_O=3.01‰~6.80‰) indicate that magmatic hydrothermal fluids constitute the primary source of ore-forming fluids, with late-stage mixing of meteoric water accompanied by water-rock interactions, driving fluid evolution from medium-high temperature/salinity to medium-low temperature/salinity. Sulfur isotopes demonstrate dominant magmatic sulfur sources with localized sedimentary sulfur contamination, while lead isotopes reveal predominantly upper crust-derived metals with minor mantle contributions. Sulfur-rich hydrothermal fluids generated by magmatic differentiation migrated along fault systems. During decompression and cooling, mixing with meteoric water altered physicochemical conditions through water-rock interactions, triggering precipitation of Ag-Zn sulfides. The deposit represents a product of interactions between magmatic hydrothermal systems and wall rocks, characterized by magma-dominated metallogenesis coupled with multi-source fluid co-evolution.
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Provenance and tectonic implications of Eocene clastic rocks in NW Borneo: constraints from stratigraphy and detrital zircon U-Pb-Hf isotopes

WANG Yiwen, QIAN Xin, WANG Weitao), ZHANG Yipeng, Gan chengshi, WANG Cheng, BAI Tianxing, ZHANG Peizhen

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Located on the southwestern margin of the South China Sea (SCS), Borneo provides a key geological window into the tectonic evolution of Paleo-Pacific Subduction and SCS.The Sintang-Semitau region, situated at the convergence of NW Borneo, SW Borneo, and Sibu-Miri tectonic zone, preserves a complete Paleozoic to Cenozoic multi-stage tectonic-magmatic-sedimentary record. This region is a key area for deciphering the tectonic evolution of West Borneo. However, previous studies predominantly focused on the Mesozoic magmatism and sedimentation, lacking the study on the Cenozoic sedimentary evolution and associated source-to-sink systems. To address this issue, we conducted systematic stratigraphic, petrographic, and in-situ detrital zircon U-Pb-Hf isotopic analyses on well-exposed clastic sandstones from the Eocene Melwai group (Payak Formation), Suwang group (Dangkan sandstone and Silat sandstone) and Teu Formation in the Sintang-Semitau region. The detrital zircons from the Payak Formation primarily exhibit age peaks at ~105 Ma and ~124 Ma, with corresponding εHf (t) values of +4.6 to +7.3 and +5.8 to +7.5, respectively. In the Dangkan sandstone, detrital zircon populations show dominant age peaks at ~86 Ma, ~115 Ma, and ~130 Ma, and yield εHf (t) values of +2.7 to +10.7, +6.3 to +9.5, and +4.2 to +15.6. The Silat sandstone displays major zircon age peaks at ~77 Ma and ~116 Ma. For the Teu Formation, characteristic age peaks occur at ~87 Ma, ~117 Ma, and ~263 Ma, with εHf (t) values of +4.3 to +11.3, -4.6 to +7.5, and -13.0 to -8.0. Regional correlation indicates that the Eocene detrital sediments were primarily sourced from the Mesozoic magmatic rocks related to the Paleo-Pacific subduction in NW and SW Borneo, with contributions from recycled proximal strata. Pre-Triassic sources are mainly derived from sedimentary and igneous rocks in the Indochina Block. Additionally, the Suwang and Melwai sandstones display features of proximal accumulation. The youngest single-grain zircon age (~46 Ma) in the Suwang Group indicates that the Eocene magmatism in NW Borneo might linke to the tectonic evolution of Proto-South China Sea.
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Characteristics and formation mechanism of pyroclasts from Dayishan Volcano in Longgang Volcanic Group, Jilin Province

Xue Chenli, Liu Yongshun, Nie Baofeng, Wang Yanan, Zhou Shuyuan, Sun Yujing, Feng Weixia, Jiang Shan

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Tectonically, Longgang Volcanic Group is located on the northeastern margin of the Sino-Korean Craton and is controlled by the Kuandian–Longgang–Dunhua deep fracture. The Dayishan Volcano in Huinan County, Jilin Province, is a typical representative of the Quaternary volcanoes on the western part of the Longgang Volcanic Group. The eruption types of the Dayishan Volcano have the stage characteristics, that is, the eruptions in the first, second and fourth stages are magmatic eruptions, while the eruption in the third stage is a weak phreatomagmatic eruption. Its chair-shaped volcanic cone is composed of pyroclastic fall deposits from multi-stage magmatic eruptions and pyroclastic fall rhythmic layers of weak phreatomagmatic eruptions. Based on the strata and petrography of the pyroclastic deposits of Dayishan Volcano, the particle size distribution, particle shape and fractal characteristics of pyroclasts was quantitatively studied from the perspectives of particle size-shape analysis and fractal theory. The particle size distributions of the Dayishan pyroclasts are all unimodal, mainly showing a coarse-grain dominance. The peak value of the particle size distribution of the weak phreatomagmatic pyroclasts in the third stage is significantly smaller than those in other stages. In terms of particle shapes, as the eruptive intensity decreases, the pyroclast shapes tend to be more irregular. However, the particle shape values of the pyroclasts in the third stage of the Dayishan Volcano are all higher than those in the other stages, indicating that the eruption products in the third stage significantly approach a regular shape. The distribution characteristics of the Dayishan particles were fitted using the multi-segment power-law method. It was found that there are four significant fractal intervals in the particle size distribution of airfall pyroclasts of magmatic eruptions, while there are three fractal intervals in the one of weak phreatomagmatic eruption. This indicates that the formation of airfall pyroclasts of magmatic eruptions is mainly affected by the initial fragmentation of magma, high-energy secondary fragmentation and wind transportation. In addition to the effects of the above factors, the pyroclast of weak phreatomagmatic eruption is also related to the explosion caused by the steam forming from the contact between magma and water.
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Permian-Triassic magmatism in southwestern Guangxi Province and its contribution to the manganese and bauxite mineralization

Xiang Zhongjin, Yan Zhen, Jia Jianliang, Fu Changlei, Li Rongzhi, Yan Quanren

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The Permian-Triassic magmatic activity in southwestern Guangxi Province was intense, and the widely exposed magmatic rocks are ideal objects for exploring the Late Paleozoic-Early Mesozoic tectonic evolution of the Nanpanjiang Basin. Meanwhile, southwestern Guangxi Province is also an important base of manganese ore and bauxite resources in China, and the intrinsic relationship between magmatic activity and the manganese and bauxite mineralization has been a hot research topic in recent years. This paper systematically summarizes the rock assemblage types, geochemical and isotopic geochemical characteristics of the Permian-Triassic magmatic rocks in southwestern Guangxi Province, and discusses their source nature, petrogenesis and relationship with manganese and bauxite mineralization. Field geological surveys and isotopic dating results show that the Permian-Triassic magmatic rocks in southwestern Guangxi are the products of three stages of magmatic activity, which are the Late Permian (~260 Ma), Early-Middle Triassic (250~241 Ma) and Late Triassic (~215 Ma) respectively. The first and third stages formed basic intrusive rocks and basalt, while the second stage formed intermediate-basic, acidic volcanic rocks and a small amount of diorite. The Late Permian basic rocks are divided into high-Ti and low-Ti groups, with the high-Ti group (>2.5 wt.%) being dominant. The high-Ti group belongs to the alkaline series, enriched in light rare earth elements (LREEs) with obvious fractionation between light and heavy rare earth elements, and enriched in large ion lithophile elements (LILEs) and high field strength elements (HFSEs), showing an upward-convex primitive mantle-normalized trace element distribution pattern. They have low (87Sr/86Sr)i values (0.7053~0.7054) and εNd(t) values close to 0 (-1.5~+1.8), similar to ocean island basalt (OIB), and are derived from the partial melting of asthenospheric mantle. The low-Ti group belongs to the tholeiitic series, enriched in LILEs, with negative Nb-Ta anomalies in the primitive mantle-normalized trace element distribution diagram and εHf(t) values less than 0, originating from the partial melting of ancient lithospheric mantle. The Early-Middle Triassic intermediate-basic volcanic rocks have SiO2 contents ranging from 53 to 60 wt.%, with high MgO (>5 wt.%), Cr and Ni, which are similar to the geochemical characteristics of high-Mg andesite/diorite. They are enriched in LILEs, with high Y, low Sr/Y and (La/Yb)N ratios, relatively large variations in (87Sr/86Sr)i values (0.7065~0.7119), and relatively uniform Nd-Hf isotopic compositions (εNd(t) = -8.8~-6.5 and εHf(t) = -5.3~-2.4). They are derived from the partial melting of lithospheric mantle metasomatized by subducted slab sediment melts (and fluids). The Early-Middle Triassic acidic volcanic rocks belong to peraluminous high-K calc-alkaline rocks, with high SiO2 content, low MgO and MnO contents, significant negative Nb-Ta anomalies, high (87Sr/86Sr)i ratios and low εNd(t) values (-11.5~-9.1), showing the characteristics of island arc volcanic rocks. The Early-Middle Triassic volcanic rocks formed in a subduction-related arc environment. The Late Triassic low-Ti basic intrusive rocks generally have low TiO2 content (<2 wt.%), belonging to the tholeiitic basalt series. They are enriched in LILEs, with obvious negative Nb-Ta and Ti anomalies, and a large range of variations in (87Sr/86Sr)i values (0.7068~0.7090) and εNd(t) values (-1.7~-8.5). They are formed by the interaction between the partial melting of enriched lithospheric mantle and asthenospheric mantle melts. In general, the Late Permian and Early-Middle Triassic magmatic activities in southwestern Guangxi Province are roughly synchronous with the mineralization ages of bauxite and manganese ore in the region, respectively. Among them, the Late Permian low-Ti basic rocks and Early-Middle Triassic acidic volcanic rocks may have provided material sources for bauxite and manganese mineralization.
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Study on fault development characteristics and analysis of influencing factors of fault-controlled hydrocarbon accumulation in the Zambezi Delta Basin based on gravity and magnetic data

Li Wen, Wang Wanyin, Ding Liangbo, Li Zhongsheng

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Fault structure as an important carrier of crustal deformation, its spatial distribution characteristics are of crucial significance for the study of regional tectonic evolution and the analysis of their influence on hydrocarbon accumulation control in petroliferous basins. Based on the gravity and magnetic anomaly data, this paper mainly uses the improved hyperbolic tangent function of total horizontal gradient (IHRHG) fault recognition technique to identify the distribution characteristics of the faults in the Zambezi Delta Basin, and the Euler deconvolution method is adopted to calculate the apparent depth of these faults. An improved fracture influence factor (IFIF) is proposed, and the petroleum exploration potential of each structural unit in the basin is predicted. This study reveals that there are 12 ultra-crustal faults and several crustal faults developed in the Zambezi Delta Basin, and an extensional-shear composite fault system dominated by extensional and strike-slip faults is constructed. The fault strikes show obvious directionality, the near SN trending faults are the most developed, followed by the NNE, NE, NNW, and NEE directions. Faults in the NW, NWW, and near EW directions are less developed. The apparent depths of the faults are concentrated between 2.5 and 10 km. Among them, the apparent depths of most ultra-crustal faults range from 2.5 to 10 km, and those of most crustal faults range from 2.5 to 7.5 km. The distribution of the IFIF values in the basin shows a zonal characteristic, which the western depression has an IFIF value of 0.35 to 1.0, the Beira High has an IFIF value of 0.0 to 0.35, and the IFIF value of the "eastern block" of the basin approaches zero. The study found that the coastal fault F3 extends from the southern margin of the Rovuma Basin southwestward to the Limpopo boundary fault zone, forming an important tectonic boundary in the basin - mountain transition zone. The ultra-crustal fault F4 extends westward from the Mozambique Channel and terminates on the west side of the Beira High, controlling the sedimentary differentiation between the Beira High and the western depression. The ocean-continent transition zone fault with a NEE-trending distribution in the central part of the "eastern block" of the basin have been identified, and The Prince Edward fault zone extends northward into the western depression and is truncated by the extensional fault F4. In addition, the hydrocarbon exploration potential of each structural unit in the basin was predicted based on the IFIF value, and the study suggests that the western depression and the Limpopo Plain have good hydrocarbon exploration potential. Further, using IFIF=0.35 as a marker, we delineated the favorable hydrocarbon exploration areas in the Zambezi Delta Basin. This study identifies the characteristics of the planar positions and apparent depths of the faults in the Zambezi Delta Basin, providing important geological constraints for the study of regional tectonic evolution. At the same time, they offer crucial tectonic evidence for deep-water oil and gas exploration.
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Three-dimensional characteristics of primary halo and implications for deep mineral exploration in the Guilaizhuang gold deposit, Pingyi, Shandong Province, China

Li Jian Lin, Zou Yan Hong, Chen Guo Dong, Mao Xian Cheng, Chen Jin, Zhang Ying Mei

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The Guilaizhuang gold deposit in Pingyi County, Shandong Province, is the first discovered tellurium-gold type epithermal deposit in China. Its deep and peripheral areas still hold significant prospecting potential, and there is an urgent need to establish an effective exploration model. In this study, 672 primary halo samples collected from 58 exploration drill holes at the Guilaizhuang gold deposit were analyzed. A three-dimensional primary halo analysis method was adopted to overcomes the limitations of traditional two-dimensional approaches. Through multivariate statistical analysis, primary halo indicator elements were identified. A 3D geochemical anomaly model was constructed to reveal the characteristics of primary halos and their correlation with mineralization while evaluating the prospecting for concealed deep ore bodies. The results show that: (1) The Guilaizhuang gold deposit exhibits an axial zoning sequence of As-Sb-Se (frontal halo), Ag-Au-Te-Pb-Zn (proximal halo), and Mo-V (rear halo). Notably, rear halo elements (Mo, V) are enriched at the top of the orebody clusters, showing a distinctive "reverse zoning" phenomenon. (2) Gold-indicating element ratios (Ag/Au, As/Sb, Zn/Pb) display a NE-SW directional zoning, consistent with the strike of the structural-cryptoexplosive breccia zone controlled by the Guilaizhuang F1 fault. (3) The frontal-rear halo multiplicative ratio[w(As×Sb×Se)/w(Mo×V)] exhibits anomalous inflection points at elevations of -750 m and -1700 m, indicating the presence of concealed orebodies at depth. The findings suggest that the mineralization at Guilaizhuang involved multi-stage hydrothermal fluids superposition. Ore-forming fluids originating from the deep southwest part of the deposit migrate upward along the structural conduits formed by the Guilaizhuang F1 fault to the near-surface, forming structural-cryptoexplosive breccia type and quasi-layered carbonate-hosted type gold orebodies. It is inferred thar the deep prospecting potential of the deposit remains promising, with the deep southern region below -750 m elevation along exploration line 35 identified as a priority target zone for further exploration.
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Major and trace elements of apatite in the Longjiaoshan tungsten deposit: implications for tungsten mineralization

Nie Liqing, Yu Shikang, Wang Fangyue, Fu Jiali, Li Xiaoyang

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The trace element characteristics of apatite offer critical insights into magma hydration, redox conditions, and source reservoir evolution during mineralization, highlighting its considerable petrogenetic significance. The Longjiaoshan deposit, a large skarn-type tungsten deposit in the southeastern Hubei ore cluster of the Middle-Lower Yangtze River Metallogenic Belt, provides new perspectives for regional metallogenic studies and mineral exploration strategies. Through detailed petrographic analysis, this study categorizes apatite samples from the deposit into three types: Ap1 (euhedral granular with smaller grain size), Ap2 (euhedral granular with coarser grain size), and Ap3 (hydrothermal vein-type apatite). Integrated analytical approaches including petrography, electron probe microanalysis (EPMA), backscattered electron imaging (BSE), cathodoluminescence (CL), and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) were systematically applied. Key findings include: (1) Systematic variations in redox-sensitive elements (Eu, Ce, V, S) across the Ap1→Ap2→Ap3 sequence indicate progressively increasing oxygen fugacity (fO2), suggesting mineralization occurred under elevated oxygen fugacity conditions; (2) The lack of significant negative Eu anomalies in Ap1 coupled with right-inclined REE patterns, and the high Sr/Y ratios and positive Sr/Y vs. La/Yb correlations in Ap2 and Ap3, collectively indicate water-rich magmatic sources; (3) Source discrimination using La/Sm vs. Sr/Th systematics points to a hybrid crust-mantle magma origin for the causative intrusions; (4) Elevated Ce/Pb ratios reflect intense W-enriched fluid activity during magmatic evolution. This study demonstrates that the high magmatic water content and strongly oxidized conditions recorded in apatite geochemistry promote effective tungsten enrichment and mineralization. These findings establish a robust theoretical framework for understanding regional metallogeny and formulating exploration criteria in similar skarn systems.
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Late Cretaceous Magmatism and Mineralization at the northern margin of the Lhasa Terrane on the Tibetan Plateau

SUN Miao, CHEN Wei, ZHANG Zhi

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The Lhasa terrane is located in the central part of the Tibetan Plateau, where a series of Cretaceous magmatic activities and related copper, gold, and iron polymetallic deposits developed. There has been considerable research on the Early Cretaceous magmatism and metallogenesis along the northern margin of the Lhasa terrane; however, research on the Late Cretaceous related studies remains weak. Based on comprehensive data collection and field investigations, this paper systematically organizes the ages of magmatism and mineralization, geochemical properties, and characteristics of the deposits related to the Late Cretaceous in the northern edge of the Lhasa Terrane, and constructs two tectonic evolution processes: the delamination stage (94-80 Ma) and the extension stage (80-70 Ma). During the delamination stage, the source of the magma was mainly the thickened juvenile lower crust, controlled by mantle convection which caused small-scale thickened crust delamination events, predominantly forming porphyry-skarn type copper and gold deposits. During the extension stage, the magma source shifted to the crust thinned after the thickened lower crust delamination, controlled by mantle-source magmatism that intruded beneath the central-northern Lhasa terrane in response to crustal extension triggered by convective thinning. This stage mainly formed skarn type iron, copper, and tungsten deposits. The magmas in the Late Cretaceous delamination stage had higher oxygen fugacity, water content, and favorable metallogenic material sources, possessing good potential for forming Cu-Au deposits; whereas, the magmatic source zones during the extension stage belonged to high-temperature melting environments, thus, exhibiting potential for forming W-Sn deposits.
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Study on the classification characteristics of garnets based on TIMA in the Chenggang uplift zone, Northern Jiangsu Province

zhaoyu, caiyitao, zhangqi, zhouqizhong, wangguoqiang, zhangxuan

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In this paper, the TESCAN Integrated Mineral Analyzer (TIMA) automated mineral analysis system was used for the first time to systematically classify garnets by species and analyze their genesis in the Chenggang uplift zone. The results show that the garnets in the zone are mainly spessartine (65.08%), followed by grossular-almandine-spessartine (11.96%), with spessartine mostly appearing in orange, maroon, and burgundy, and grossular-almandine-spessartine mainly in pink. The numbers of pyrope end-members in pink, orange, maroon, burgundy, and purplish-red garnets are 206, 93, 10, 1, and 1 grains, respectively. Combining the information of pyrope types in other areas and the results of Cr-K surface scanning, some of the pink and orange pyrope belong to eclogite-type pyrope, while the purplish-red pyrope is presumed to be chromium-bearing pyrope due to its moderate chromium content, suggesting that this area has geological potential for diamond mineralization. Through automated spectral scanning and database comparison, the TIMA technique has efficiently identified nearly 2000 garnet minerals and successfully recognized pyrope end-members related to diamond mineralization. This not only verifies the technique""s feasibility in mineral classification and mineralogical identification but also provides a new technological pathway for studying mineral genesis and predicting mineralization.
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Geological and Geochemical Characteristics of the Xialei Manganese Deposit in Guangxi and their Constraints on Different Manganese Mineralization Mechanisms

guoningning, gaozhaofu, jiajianliang, yanzhen, xiangzhongjin, maqing, wangda, zhuxiangkun

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The Xialei Manganese Deposit in Guangxi is the most important super-large sedimentary manganese deposit of the Late Devonian in South China. There are two different views on the genetic mechanism of its typical manganese carbonate ores: one is oxidation precipitation-diagenetic transformation, and the other is direct precipitation in a reducing environment. Based on previous studies, this paper systematically analyzes the mineral paragenetic association, major and trace (rare earth) elements, and C-O isotope geochemical characteristics of typical rocks and ores in the Xialei Manganese Deposit, revealing the synergistic control of ore-forming material sources and redox conditions on manganese ores of different grades.In the low-grade manganese ores (MnO<25%) of the Xialei Manganese Deposit, rhodochrosite develops heteronuclear structures and is paragenetic with microcrystalline pyrite, indicating a direct precipitation process in a reducing (sulfidic) water environment. Meanwhile, their geochemical characteristics—including high Fe/Mn ratios, significant positive Eu anomalies (average δEu=1.32), relatively concentrated and generally slightly positive δCe values (ranging from 0.94 to 1.30, with an average of 1.12), and relatively negative δ13C values (average=-5.05‰)—collectively indicate that the low-grade manganese ores are products of direct precipitation, where hydrothermal Mn2? in deep water directly combines with dissolved CO?2? in the sub-deep reducing water environment.In contrast, the high-grade manganese ores (MnO≥25%) exhibit systematic geochemical differences, such as insignificant positive Eu anomalies (average δEu=1.11), significantly expanded variation range of δCe values (0.81–1.64), low Fe/Mn ratios, and more negative δ13C values (average=-7.72‰). Combined with evidence of residual manganese oxides reported in previous studies, it is indicated that the high-grade manganese ores underwent a phase transition process of "oxide precipitation → organic matter-driven reduction" after sufficient mixing of hydrothermal fluids and seawater. In conclusion, the formation of manganese carbonate ores with different grades in the super-large Xialei Manganese Deposit in Guangxi involves two distinct metallogenic mechanisms, which are jointly controlled by hydrothermal activities and the redox (sulfidic) stratified water environment. This may be genetically related to the contemporaneous intracontinental rifting-magmatic hydrothermal events and mass extinction events.
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Analysis of the Metallogenic Regularity and Material Sources of Critical Metals in the Aluminum-Bearing Rock Series of the Upper Permian Heshan Formation in Western Guangxi

Qin Feng

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Bauxite deposits are one of the important sources of critical metal mineral resources. The western Guangxi region is a major bauxite-producing area in China. Carrying out research on critical metal elements in the aluminum-bearing rock series of the Upper Permian Heshan Formation (P3h) in this area can provide reference for the comprehensive exploration and evaluation of sedimentary bauxite deposits, and help improve the comprehensive utilization level of minerals in the region. Based on the latest exploration results of sedimentary bauxite deposits in western Guangxi, this paper summarizes the planar distribution rules of associated critical metal elements in each deposit, makes a detailed analysis of the aluminum-bearing rock series, focuses on studying the enrichment rules of critical metal elements in the profile, and discusses the metallogenic material sources of the aluminum-bearing rock series and critical metal elements. The study shows that critical metals Ga, Li, Nb and rare earth elements (REE) in the aluminum-bearing rock series of the Upper Permian Heshan Formation (P3h) in western Guangxi have obvious enrichment phenomena, and critical metal elements are mainly enriched in bauxite (ore) rocks in the middle of the aluminum-bearing rock series and ferruginous-aluminous rocks in the lower part. The sources of the aluminum-bearing rock series and critical metal elements are multigenic. The basement strata provide part of the material sources for mineralization, and the intermediate-acid volcanic clastics from the Late Permian volcanic island arc are also important metallogenic material sources.
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Petrogenesis and geodynamic significance of late Neoarchean quartz dioritic gneisses in the Jiaobei terrane, North China Craton

YAO Jiachen, WANG Wei, YAO Xiaofeng, WANG Zongqi, YANG Weibo, HU Jincheng, LIANG Xueyin

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The origin of early continental crust is a hot issue in early Precambrian research. Since the intermediate average composition of the continental crust, unraveling the petrogenesis of intermediate rocks and the processes of crust-mantle interaction is key to understand the formation of continental crust and related geodynamic regimes. In this study, the late Neoarchean quartz dioritic gneisses exposed in the Jiaobei terrane of North China Craton were selected as the research object, and the zircon U-Th-Pb-Lu-Hf isotopes and whole-rock major and trace elements were analyzed. Based on these data, comprehensive studies of the spatial and temporal distribution, geochemical characteristics, and crust-mantle interaction were conducted to decipher the origin mechanism of these intermediate magmas. The results show that the late Neoarchean quartz dioritic gneisses of Jiaobei terrane are mainly exposed in the northeastern part of Qixia, Majiayao, Huangyandi, Shilizhuang, and northern Dachai, with crystallization ages of 2563~2500 Ma. These quartz dioritic gneisses are further divided into >2.55 Ga and <2.55 Ga groups. The >2.55 Ga quartz dioritic gneisses show hornblende as the major mafic minerals, with depleted zircon εHf(t2) values. They have relatively low SiO2 (mostly of 54.59%~59.27%), Mg# (37.59~50.51), and Sr+Ba (357 ×10-6~1166 ×10-6), belonging to the low- to medium-K series. Meanwhile, they show moderately fractionated chondrite-normalized rare earth elements (REE) patterns with low (La/Yb)N (3.92~7.12). In comparison, the <2.55 Ga quartz dioritic gneisses contain less volume of mafic minerals that are dominated by biotite, with less depleted zircon εHf(t2) values. These samples exhibit relatively high SiO2 contents (55.48%~63.54%), Mg# (45.43~63.24), and Sr+Ba (866 ×10-6~3480 ×10-6), belonging to the medium- to high-K series. In addition, they have strongly fractionated chondrite-normalized REE patterns with high (La/Yb)N (10.84~65.67), which are chemically analogous to those of Archean sanukitoids. Detailed petrogenetic studies reveal that the >2.55 Ga quartz dioritic gneisses were derived from the partial melting of the depleted mantle weakly modified by the metasomatism of basaltic crustal melts. In contrast, the <2.55 Ga quartz dioritic gneisses were formed by the partial melting of a less depleted mantle that was strongly metasomatized by sediment melts. Taken together, the late Neoarchean quartz dioritic gneisses in the Jiaobei terrane record crust-mantle interactions involving the recycling of crust-derived materials and mantle metasomatism, which could mark an important episode of crustal growth that was likely evolved under a plate subduction setting during the late Neoarchean.
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Prospecting prediction of karstic bauxite driven by deep learning: A case study in the Pingguo area, western Guangxi, China

Xie Qili, Lou Debo, Song Guoxi, Meng Xianglun

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As a strategically critical resource, bauxite exploration requires urgent advancement. To address the limitations of traditional prospecting methods in efficiency and accuracy, this paper takes the karstic bauxite in the Pingguo area of western Guangxi as the research object and proposes a deep learning-based prospecting prediction method driven by multi-source data fusion. Based on the U-Net benchmark model, the study focuses on the impact of constructing multi-source geoscience data training sets using the sliding window technique and optimizing network architecture parameters on model performance. It also quantitatively evaluates model performance by introducing a composite score S (weighted by the intersection over union IoU, F1 score, and normalized training time Tn) and subsequently constructs a deep learning-based prospecting prediction model. The results show that:(1) When constructing the dataset using sliding window technology, the S-value with a 75% overlap rate increased significantly by 71.04% compared to that with a 0% overlap rate, indicating that this setting can effectively enhance the data and significantly improve model performance; (2) In model architecture optimization, the optimal combination was determined through controlled experiments (64 base channels, replicate padding, SE+ module, ELU activation function, and Cross-Entropy+Dice composite loss function), which further increases the S-value by 8.72%, significantly improving the recognition capability for complex geological features.Finally, prospecting prediction was conducted in the target area combined with multi-source data, successfully delineating five prospecting targets. The integration of multi-source data and deep learning technology enriches the prospecting prediction theory for karstic bauxite and provides scientific basis for exploration of this deposit type.
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Crustal structure analyze and three-dimensional modelling in front area of Sichuan-Yunnan rhombic block

Tian Tian, Jiang Wenliang

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We constructed the three-dimensional crustal model of the front area of Sichuan-Yunnan rhombic block using the iterative forward-inversion method. The gravity anomaly data, the multi-scale wavelet decomposition method and Parker interface inversion Parker interface inversion method are used during the crustal layer modelling. The magnetic anomaly data and the three-dimensional interpretation method are used in the fault modelling. The fault models we constructed in this area are the regional large fault including Lancangjiang fault, Wuliangshan fault, Honghe fault, Ailaoshan fault, Yuanmou fault, Xiaojiang fault and Shizong fault. The results show that the depth of the bottom of the upper crust in this area is between 9 and 18 km, and its relief is mainly controlled by the main faults. The depth of the bottom of the middle crust is between 25 and 34 km, and the fault control is weakened, showing the overall rise from north to south; The depth of Moho is between 31-41km, showing the crust thinning from north to south. The depth of the model constructed in this paper has similar range and significant correlation with the depth of Crust1.0 model-the correlation coefficient are greater than 0.5 and 0.8 of bottom of the middle crust and the Moho respectively.
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Low-Amplitude-Weak Inversion Anticline Structures in the Southern Part of Xihu sag: Genesis, Evolution, and Hydrocarbon Potential

Jiang Yi Ming, Tang Xian Jun, He Xin Jian, Zhu Hong Hao, Zhang Wu, Zhong Rong Quan

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The central anticline belt in the Xihu sag: is a key area for hydrocarbon accumulation. However, previous studies have paid limited attention to low-amplitude-weak inversion anticline structures in this region. These structures differ significantly from the widely developed high-amplitude-strong inversion anticlines in terms of their genesis and evolution. Based on the latest 3D seismic data, this study conducts a detailed structural analysis of the H and Q anticlines in the low-amplitude-weak inversion anticline zone. It reveals their genesis, evolution, and impact on hydrocarbon accumulation. The research shows that low-amplitude-weak inversion anticline structures formed as cover anticlines during the rift phase under a paleo-uplift background and were finalized by compression-inversion during the Longjing Movement. These structures have a "early extension-late weak compression" composite genesis. During the extension phase, the early cover anticline morphology and flower-like fault systems formed simultaneously. Moreover, the intensity of tertiary fault activity in the wings of the anticline has always been greater than in the core of the anticline throughout the structural evolution process. Based on the new understanding of the evolution of low-amplitude-weak inversion anticline structures, this study identifies favorable conditions for hydrocarbon accumulation: "paleo-uplift background and cover anticline-controlled hydrocarbon migration and accumulation," "structure-lithologic traps controlled by extension-compression interaction," and "key hydrocarbon accumulation periods with source-fault-sand configurations in the wings of the anticline." These factors highlight the exploration potential for structure-lithologic gas reservoirs in the wings of the anticline. This research deepens the understanding of hydrocarbon enrichment patterns in inversion structures in the central anticline belt and has played a key role in breaking through natural gas exploration in the southern part of Xihu sag.
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Late Cenozoic vertical-axis rotation of the Tarim Basin- magnetic fabric evidence from the Mazatagh thrust belt

Li Bingshuai, Dou Jiahe, Yan Maodu, Peng Heng, Song xiangsuo, Zhang Peng

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Surrounded by the West Kunlun Mountains and the Tian Shan fold-and-thrust belts, the Cenozoic vertical-axis rotations of the Tarim Basin are crucial for understanding the kinematic processes of the western Himalayan syntax and the Tian Shan orogeny. However, the Cenozoic rotation pattern and magnitude of the Tarim Basin remain disputed. This study conducted detailed magnetic fabric analyses on Late Cenozoic sediments along the Hongbaishan profile at the Mazatagh thrust belt in the central Tarim Basin. By examining the features of magnetic fabrics, paleocurrent directions and provenance, we concluded that the magnetic fabrics at Hongbaishan were embryonic tectonic fabrics, which can reflect paleostress directions. After rotation correction, the compressional direction during the Late Cenozoic at Hongbaishan was NNE, consistent with the upper-crust vectors revealed by GPS observations. This pattern is primarily related to the nearly N-S-directed India-Eurasia collision and the continuous indentation of the Indian plate into Eurasia since the Cenozoic. This indicates that compressional stress has propagated into the interior of the Tarim Basin since at least ~9.7 Ma from the collisional zone. The compressional stress directions at Hongbaishan, as revealed by magnetic fabrics, indicate that the Mazatagh region has undergone an absolute ~7.0° clockwise rotation since ~7.6 Ma (relative to the spin axis of the Earth). These rotation patterns and magnitudes are consistent with results from classical geological methods and GPS observations and may represent the true rotational features of the Tarim Basin since the Late Cenozoic. However, previous paleomagnetic results surrounding the Tarim Basin mostly reflect local rotation features within the peripheral orogeny. The Late Cenozoic clockwise rotations of the Tarim Basin may be related to the northward indentation of the Pamir salient or the heterogeneity of the Tian Shan, leading to the E-W inhomogeneity of the upper crust.
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Reconstruction of the sedimentary environment characteristics of the Subei Basin based on grain size end-member analysis

Bao Jing

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Grain size is a basic characteristic of sediments, which can reflect the dynamic conditions of sediment transport and sedimentary processes. Therefore, it has been widely used in palaeoenvironmental studies. However, due to the influence of various factors on the depositional environment in the basin, and the complexity of provenance and depositional dynamic conditions, it is difficult to understand the implications of each grain size component only based on grain size parameters. By extracting and analyzing the environmental-sensitive grain size components of sediments, it is possible to accurately reconstruct the hydrodynamic conditions and regional climate during geological period. In this study, the Miocene fluvial-lacustrine sedimentary deposits (~22.8-9.0 Ma) along the Tiejianggou section at the Subei Basin were analyzed by using a depositional grain-size end-member analysis model, and four end-members that could represent the depositional environments were obtained. Through comprehensive analyses of sediment grain size characteristics and end-member components, the sedimentary processes along the Tiejianggou section can be divided into four stages. (1) During ~22.8-21.4 Ma, the end-member component one (EM1) (representing lacustrine fine silt) and EM2 (representing lacustrine medium silt) wavelike decreased, while EM3 (representing river coarse silt) and EM4 (representing fan deltaic sandy) wavelike increased, the grain size coarsened upward and poorly sorted, indicating the depositional environment were dominated by low-energy fan deltaic facies with great fluctuations. (2) During ~21.4-17 Ma, EM1 and EM2 significantly increased, while EM3 and EM4 decreased, the grain size fined upward and was dominated by static deposition of fine sand with good sorting, indicating the strengthening influence of lakes and the depositional environment transited to a stable shallow lake or lacustrine face. (3) During ~17-14 Ma, EM1 decreased, EM2 and EM3 were relatively stable with EM3 accounting for the highest proportion, EM4 increased slightly, the grain size coarsened again and were dominated by coarse silt from river suspension input with poor sorting, indicating an unstable depositional environment with low-energy fluvial deposition. (4) During ~14-9 Ma, EM1 wavelike decreased, EM2 and EM3 were relatively stable, and EM4 continued increasing. The grain size significantly coarsened and was dominated by coarse sand from saltation and suspension input and the sorting was poor with enhanced hydrodynamic forces, indicating the most unstable depositional environment that was dominated by high-energy fan delta phases. The depositional environment of the Tiejianggou section transitioned from the early fan delta to the stable lacustrine and finally evolved into the high-energy fan delta phase, and the staged evolution of hydrodynamic conditions from weak to stable, and to enhanced ones. By comprehensive analyses of previous results, we concluded that the depositional environment and hydrodynamic changes during the middle to early Miocene (~22.8-14 Ma) in the Subei Basin were mainly dominated by the regional warm and humid climate, while the high-energy environment during the middle to late Miocene (since ~14 Ma) was jointly dominated by the uplift of the Tibetan Plateau and regional aridification.
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Enrichment of Li, Th, Mo, Pb, and U in Coals from the Taiyuan Formation, Jin-cheng Mining Area, Southern Qinshui Basin: Geological Controls and Implications

Guo Jun, Sun Beilei, liu Chao, Xie Xichao, Li jian

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To investigate the distribution, occurrence modes, and enrichment cause of trace elements in coals from the southern Qinshui Basin through mineralogical and geochemical analyses of No. 9 and No. 15 coal seams in the Tai-yuan Formation from Tian'an Hongxiang Mine, Jincheng Mining area. The results demonstrate that: (1) The mineral composition in the coal is dominated by kaolinite, pyrite, calcite, and anatase. The No. 9 coal seam has a content of 37.1 μg/g (coal basis), 2.7 times than that world hard coal. The No. 15 coal seam exhibits significant Li enrichment (108 μg/g, coal basis), equivalent to 7.8 times higher than the average values world hard coal, along with moderate enrichment of Zn, Mo, Pb, Th, and U. Li primarily occurs in clay minerals, and Mo and Pb are mainly associated with pyrite (with minor Mo in organic matter and sulfates). Th is hosted in anatase and clay, the enrichment of U is primarily associated with semifusinite in the inertinite. (2) Li and Th are mainly controlled by the supply of the gra-nitic terrigenous material from the North Qinling orogenic belt. The weak hydrodynamic conditions and humid trop-ical climate promoted clay mineral formation which provided a host for Li and Th. (3) The peat formed in alkaline sedimentary environment with weak hydrodynamics. The enrichment of Mo, Pb, and U was significantly influenced by seawater, where Mo and Pb combined with S2? to form sulfides under reducing conditions (with minor Mo in sulfates and organic matter). Alkaline-reducing peat bogs favor the precipitation of UO22+ ions, and the occurrence of U in coal is primarily associated with inertinite.
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Fluid characteristics, telluride forming conditions and their constraints on the process of gold enrichment in Tantou deposit, western Henan Province

YaoDongdong, ChaoWeiwei, LengChengBiao, YeHuishou, Wang Dazhao, GaoMing, CaoYuan

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The Tantou deposit is located in the Xiong’ershan district, the southern margin of the North China Craton. Various types of tellurides are developed and closely associated with native gold. However, the characteristics of fluids, the telluride forming conditions and their constraints on gold enrichment remain unlcear. Based on the detailed division of metallogenic stages, the fluid properties, tellurides and native gold geochemical compositions analyzed in detail by microthermometry, H-O isotopes, scanning electron microscopy and electron probe microanalysis. Tantou gold deposit can be divided into four metallogenic stages: (1) K-feldspar-quartz stage; (2) Quartz-pyrite stage; (3) Sulfide-telluride stage; (4) Quartz-carbonate stage. Gas-liquid inclusions are mainly developed in the quartz-pyrite stage. The homogenization temperatures for the quartz-pyrite stage and the sulfide-telluride stage are 275–363°C and 258–285°C, respectively, with salinities of 5.01%–9.32% NaClequiv and 5.62%–8.10% NaClequiv, densities of 0.68–0.84 g/cm3 and 0.71–0.86 g/cm3, pressures of 5.5–18.3 MPa and 4.1–6.5 MPa, and corresponding mineralization depths of 0.55–1.83 km and 0.41–0.65 km, respectively. Telluride are composed of petzite, sylvanite, stützite, empressite, hessite, altatite, lingbaoite, melonite, coloradoite and tellurium. Through the analysis of mineral assemblages and physical and chemical conditions, the formation conditions of quartz-pyrite stages are T = 300℃, log?O2 = -36.8~-32.1, pH = 3.7~5.7, log?Te2 = -18.0~-10.9, log?S2 = -11.6~-6.8, while that of sulfide-telluride stage are T = 250℃，log?O2 = -37.5~-31.8，pH = 3.9~5.9，log?Te2 = -12.9~-9.4，log?S2 =-14~-9.5. From the quartz-pyrite stage to the sulfide-telluride stage, as the ore-forming depth becomes shallower, the temperature and log?S? of the fluid decrease, while the log?Te? increases. The salinity, density, log?O?, and pH remain essentially unchanged. The early stage (quartz-pyrite stage) mainly precipitated Te-Au-rich pyrite through water-rock reaction, and the late stage (sulfide-telluride stage) mainly formed a large amount of sulfide, telluride and natural gold through fluid mixing. The tellurides start forming a metallic melt, which continuously extracts Au elements from the fluid, leading to the co-enrichment and precipitation of tellurides and gold.
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Metallogenic process and control factors of large-scale sedimentary manganese carbonate deposits in Zunyi area, northern Guizhou

XU Hai, YIN Runsheng, Gao Junbo, YANG Ruidong, YANG Chenchen, ZHAI Mengdi, ZHAO Yinqiang

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Sedimentary manganese (Mn) carbonate ores are an important type of Mn deposit, and serve as a critical carrier for investigating the redox state of Earth's surficial system. The precipitation mechanism, metallogenic process and paleoenvironment reconstruction of sedimentary Mn carbonate deposit are key issues of concern to geologists. In this study, we investigated petrographic, geochemical and C isotopic characteristics of Permian the Zunyi Mn carbonate deposit, to explores the material source, precipitation mechanism, metallogenic environment, and control factors. The Zunyi Mn deposit developed hydrothermal brecciated Mn ores crosscut by Mn-bearing calcite veins, and numerous hydrothermal origin minerals (e.g., chalcopyrite, siegenite, and molybdenite, etc.) were observed in Mn ores. Combined with the element ratio of the authigenic carbonate for Mn ores (e.g., Fe/Ti, Ni/Co, and Cu/Zn ratios), REY differentiation characteristics, and genesis diagrams reveal that the ore-forming materials originated from the volcanism related hydrothermal activities during the late stage of Middle Permian. The preserved original Fe-Mn oxide residues within Mn carbonate minerals, coupled with Mn ores exhibit high REY concentration (mean 143.6×10-6) and negative δ13Ccarb value (mean -6.20‰), and δ13Ccarb value is negatively correlated with MnO content (R2=0.51) and positively correlated with CaO+MgO content (R2=0.52), suggesting that Mn carbonates were formed via the diagenetic reduction of Mn oxides. Lithofacies, sedimentary sequences, and redox indicators (e.g., MoEF, UEF, and Ce anomalies) indicate that the basin water column shifted from euxinic-anoxic to suboxic-oxic conditions during Mn precipitation. Integrating the global/regional paleotectonic, paleogeographic and paleoceanic evolution, the Zunyi Mn deposits are product of the combined effects of the coeval paleotectonic-magmatic-hydrothermal activities, paleogeographic, and paleoceanic environmental evolution. The ELIP uplift caused the formation of the Qianzhong rift basin and the rift systems and magmatic-hydrothermal activities within the basin, provided the essential material source, migration channel, and precipitation site for Mn mineralization. The formation of the redox stratified water column within the basin provides the necessary conditions for the initial enrichment of Mn(Ⅱ). The dual effects of the sustained ELIP uplift and large-scale regression driven the bottom water column shift from anoxic to suboxic-oxic conditions, triggering large-scale Mn(Ⅳ) oxides precipitation, and subsequently transformed into Mn carbonates via diagenetic reduction.
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Quantitative Response of Turbidity Current Confluence Processes to Salt Diapirs in Submarine Canyons: A Case Study from the Northern Gulf of Mexico Continental Slope

XU Hongxiang, GE Zhiyuan

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Objectives: Quantitative analysis of submarine canyon confluence processes in salt diapir-affected regions is critical for understanding deep-water sedimentary systems, yet the three-dimensional hydrodynamic mechanisms and morphodynamic interactions under structural controls remain poorly understood. This study investigates the Dorsey-Sounder Canyon System in the northern Gulf of Mexico to systematically reveal the salt diapir-driven three-dimensional morpho-hydrodynamic evolution, sediment partitioning patterns, and associated depositional mechanisms. Methods: Integrated analyses of high-resolution 3D seismic data, automated canyon morphology identification, and hydrodynamic quantitative modeling were combined to reconstruct the spatiotemporal evolution of the canyon confluence zone. Multidisciplinary approaches focused on: (1) quantifying morphological parameters, (2) analyzing flow pathway dynamics through hydraulic modeling, and (3) deciphering erosional-depositional patterns under salt tectonic constraints. Results: The modern trunk canyon comprises an eastern tributary and a post-confluence segment, with the confluence point migrating ~1 km southeastward from the initial scour zone, forming a trumpet-shaped morphology characterized by pronounced widening and deepening. Salt diapirs dominantly controlled the confluence process through three-dimensional mechanisms: (1) Planar structural steering confined canyon pathways and defined the confluence zone; (2) Enhanced vertical confinement promoted incision and erosional amplification; and (3) Differential diapir growth rates governed confluence migration. These processes drove asymmetric sediment partitioning and distinct architectural stacking in the deep-water system. Conclusions: This work establishes the first integrated 3D model of salt diapir-controlled canyon confluence processes, elucidating how salt tectonics regulates sediment routing and reservoir heterogeneity in deep-water settings. The findings provide a predictive framework for analogous salt-affected basins, emphasizing the coupling between structural evolution and sedimentary responses in source-to-sink systems. This advances theoretical foundations for hydrocarbon reservoir prediction in complex deep-water environments.
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Research progress and prospect of the ophiolite peridotite in Turkey

CHEN Bohao), LIAN Dongyang), CAI Pengjie, BO Rongzhong)

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Turkey ophiolites are distributed across several tectonic units, such as the Northern Anatolian Belt, the Tauride Ophiolite Belt, and the Southern Ophiolite Belt. These ophiolites represent remnants of the Tethyan oceanic lithosphere and reflect the complex tectonic evolution of the region. Studies show that the mantle peridotites within these ophiolites, including harzburgite, dunite, and lherzolite, are extensively serpentinized and exhibit mineralogical and geochemical affinities with peridotites formed in abyssal and forearc settings. The mineralogical characteristics of mantle peridotites, such as the chemical compositions of olivine, orthopyroxene, clinopyroxene, and the Cr# and Mg# values of chromite, provide crucial insights into their melting history and tectonic origin. Geochemical analyses further reveal that mantle peridotites in Turkish ophiolites exhibit significant variations in rare earth element (REE) and trace element distributions, indicating varying degrees of partial melting and subsequent melt-rock interactions. Lherzolites display a left-leaning REE pattern with light REE depletion, while harzburgites and dunites show “U”- or “V”-shaped REE patterns resulting from interaction with LREE-enriched melts/fluids in suprasubduction zone settings. Chromitite research is a key focus within Turkey ophiolites, especially the distribution and genesis of podiform chromitites, which provide valuable guidance for chromitite exploration. Studies indicate that chromitite formation is influenced by a combination of mantle partial melting, melt-rock interaction, and magmatic fractional crystallization, with contributions from deep mantle materials. The mantle-crust transition zone and the upper part of the mantle in supra-subduction zone settings are identified as critical areas for chromitite formation. Moderately depleted peridotites, especially harzburgites associated with dunites, are important exploration indicators, while large-scale dunites of boninitic affinities provide favorable spatial conditions for chromitite enrichment. Additionally, the preservation and exposure of ore-bearing bodies, closely tied to the degree of erosion, are crucial factors to consider during exploration. In conclusion, the study of Turkish ophiolites not only deepens the understanding of mantle dynamics and plate tectonics but also provides scientific guidance for chromitite exploration. By integrating the petrological and geochemical characteristics of mantle peridotites, focusing on favorable tectonic settings, large-scale dunite regions, and moderately eroded ore-bearing bodies, future chromitite exploration efforts are expected to achieve greater efficiency and yield more significant results.
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Study on topographic amplification effect of strong earthquake ground shaking in the Yarlung Tsangpo Grand Canyon - A case study of the 2017 Miling Ms6.9 earthquake

Li Haowen, He Kai, Li Bin, Wan Jiawei, Gao Yao, Wang Wenpei, Cui Fangpeng

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The Ms6.9 magnitude earthquake occurred in the Yarlung Tsangpo Grand Canyon region of Minlin City, Tibet Autonomous Region, at 06:34 on November 18, 2017, which led to a number of large-scale landslide debris flows and river blockage in the uninhabited area of the Grand Canyon, resulting in serious hazards. In this paper, we use the 3D spectral element method SPECFEM3D numerical simulation program, combined with remote sensing image data, to simulate and study the ground vibration amplification effect of the complex terrain conditions of the Grand Canyon under the effect of the Ms6.9 magnitude earthquake in Minlin. The results show that: (1) when the seismic wave propagates along the Xixingla rupture, the velocity amplitude amplification occurs in front of the fault rupture, and the uneven energy of the seismic wave and the amplification of the velocity amplitude in many places occur when passing through the high and very high mountainous terrain of the Grand Canyon. (2) The simulated epicenter PGA of the Miling earthquake reached 4m/s2 (0.4g), and the high amplitude area was concentrated near the Xixingla rupture, which was mainly divided into the glacier aggregation area on the north side of the Gyala Peri Peak, the Jiala - Baimagouxiong section of the Yarlung Tsangpo River, the Xixingla - Naiqu section, and the Zhaqu - Duoka section. (3) The PGA of the Yarlung Tsangpo Grand Canyon in the area of rapid topographic change can be 1.97 m/s2, and the amplification rate can be up to 4 times from the bottom to the top of the mountain, and the maximum PGA of 4 m/s2 was detected above the concave and convex body of the seismic source model (4) Three major landslide-intensive zones appeared in the Yarlung Tsangpo Grand Canyon after the Milling earthquake, which were the Jiala-Baimagouxiong section, the Xixingla-Naiqu section, and the Zhaqu-Duoka section, and the PGA high amplitude area coincides with the distribution of landslide-intensive development area. The discussion can be concluded that the Milin earthquake has a non-negligible influence on the occurrence of high watershed-based geohazards in the Grand Canyon area after 2017.
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Rapid exhumation in Hainan Island and its implications for the formation of the South China Sea

Zhang Yulian, Zhang Wanfeng, Zheng Dewen, Li Chaopeng, Yu Jingxing, Li Pengfei

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The paleographic pattern of the southern margin of the South China Block before the Cenozoic is essential for understanding the formation and evolution of the South China Sea. Hainan Island, located at the northern margin of the South China Sea and adjacent to the southern edge of the South China Block, serves as a key region for investigating the paleographic features of the passive continental margin of the South China Sea. In this study, we conducted biotite 40Ar/39Ar geochronological analysis on granites from the Triassic to Cretaceous on Hainan Island, to explore the exhumation characteristics and topographic evolution during the Mesozoic. The results show that the cooling ages obtained from biotite 40Ar/39Ar range from 107 to 92 Ma The consistent cooling ages of granitic plutons along the periphery of Hainan Island suggest that the Hainan Island underwent rapid cooling during this period. By synthesizing the available biotite 40Ar/39Ar age data, we observe a “younger on the periphery, older in the center” cooling age distribution, indicating that during this period, the peripheral regions of Hainan Island experienced more significant exhumation than the central areas during this time. It is inferred that during the Late Mesozoic, Hainan Island exhibited a “high in the periphery, low in the center” topographic pattern. Based on this observation, we evaluate and select samples suitable for paleoelevation reconstruction, using detrital zircon Eu/Eu* anomalies and whole-rock (La/Yb)N and Sr/Y ratios. The results of paleoelevation reconstruction of the peripheral regions of Hainan Island during the Cretaceous indicate that the paleoelevation in this period exceeded 3000 meters. Rapid exhumation of the peripheral granitic plutons provided a substantial detrital material to the low-lying Baisha Basin in the central region, further supporting the “higher in the periphery, lower in the center” topographic feature. A comprehensive analysis of the geochronological, geochemical, and provenance data from the South China Sea peripheral blocks reveals that the region experienced a widespread exhumation/cooling event during the Early-Late Cretaceous. This suggests that, at least during the Late Mesozoic, the southern and northern margins of the South China Sea still existed as a unified entity, implying that the initiation of the South China Sea rifting occurred after this period.
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Paleoclimate change and its driving mechanisms in the Gonghe Basin (NE Tibetan Plateau) in the Middle to Late Miocene

Luan Tianxinag, Zhang Bo, Zhang Jinjiang

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The paleoclimate of the northeastern Tibetan Plateau during the Middle to Late Miocene may have been controlled by tectonic uplift in the northeastern plateau and global cooling. To investigate the impact of global climate change and tectonic activity on regional climate, as well as to enhance understanding of the interactions among Earth's spheres, this study focuses on the Miocene sediments from the Gonghe Basin in the northeastern Tibetan Plateau. By integrating existing stratigraphic paleomagnetic age data with comprehensive analyses of branched glycerol dialkyl glycerol tetraethers (brGDGTs), total organic carbon isotopes, total organic carbon content (TOC) and heavy mineral composition, we reconstructed the environmental evolution history of the Gonghe Basin during this period. The results show that from 14.5 to 8.7 Ma, the paleotemperature reconstructed by brGDGTs steadily decreased (by about 2.3 ℃), the total organic carbon isotopes increased from -25.23‰ to -24.88‰, pH value increased from 8.1 to 8.7, and TOC decreased by ~0.05%, indicating an intensification of aridification. From 8.7 to 6.8 Ma, the total organic carbon isotope decreased from -24.88‰ to -25.23‰, and the pH decreased from 8.7 to 8.2, indicating that the aridification was alleviated. Compared with the previous period, the cooling rate accelerated (increased from 0.4 ℃/Ma to 1.7 ℃/Ma), and the content of unstable heavy minerals increased. It is inferred that during this period, the significant uplift of the Elashan and Qinghai Nan Shan around the Gonghe Basin formed a topographic barrier to the southeast monsoon, leading to opposite trends in temperature and humidity within the basin. By integrating the tectonic and climatic records from the northern Tibetan Plateau, we believe that the alleviation of aridification in the study area and regions to its east during 9~7 Ma primarily responded to the orographic rainfall effect caused by tectonic uplift. In contrast, the continued aridification since the Middle Miocene in areas to the west of the study area, such as the Qaidam Basin and Tarim Basin, was controlled by both global cooling and tectonic uplift.
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Tectono-thermal evolution of the basin-range system in the north margin of Erlian Basin and its geological significance

ZhouGuiLin, LI Ke, TANG Jianzhou, ZHANG Zhicheng, ZHANG Huaihui, DING Cong

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The Erlian Basin is a group of fault basins formed under the Mesozoic extension system in central Inner Mongolia. It is of great significance to study the characteristics of tectono-thermal history of the basins and identify the evolution law of tectono-geomorphologic exhumation in Inner Mongolia and its adjacent areas for understanding the dynamic mechanism of multi-tectonic domain superimposed transformation in NE China during the Mesozoic. Here, the apatite fission track (AFT) method is used to study the tectono-thermal evolution of the Bayindulan Sag and the Bayinbaolige Uplift in the northern margin of Erlian Basin. AFT dating results showed that the AFT ages in the Sag are 65.6±8.8~245.2±17.3 Ma, and the mean track lengths are 12.17±0.3~13.32±0.2μm. The ages of AFT in the Uplift region are 182±11~238.8±8.7 Ma, and the mean track length was 12.86±0.30~13.46±0.16 μm. The results of thermal history modeling show that the northern margin of Erlian Basin mainly experienced three stages of cooling, namely, late Paleozoic to Middle Jurassic (270-160 Ma), Late Jurassic to Early Cretaceous (160-100 Ma) and Late Cretaceous (100-70 Ma). Combined with the regional data, the tectono-thermal process in central Inner Mongolia presents three stages of evolution, and the late Paleozoic-Triassic uplift is related to the closure of the Paleo-Asian Ocean；During the Jurassic and Early Cretaceous, the central region of Inner Mongolia was affected by the extension collapse after the closure of the Mongol-Okhotsk Ocean and the subduction of the Paleo-Pacific plate. In the Late Cretaceous, the collision of East Asian continental margin blocks caused regional tectonic inversion in Erlian Basin. After the Late Cretaceous, the central part of Inner Mongolia did not experience significant cooling exhumation and the planation surface of Inner Mongolia Plateau was basically formed.
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Evolution of ore-forming fluids in the deep polymetallic mineralization in western Xiangshan uranium ore field, Jiangxi Province, China: evidences from altered wall rocks

LiuJungang, LI ZiYing, ZHANG WanLiang, NIE JiangTao

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The Xiangshan uranium ore field, the largest hydrothermal uranium ore field in China, is hosted in early cretaceous felsic volcanic rocks. In recent years, , a discovery of hidden lead-zinc-silver mineralization in deep reach was achieved through NO.3 sientific deep drilling(CUSD3) in western Xiangshan uranium ore field. In this paper, the petrography and geochemistry of altered wall rock at different stages of polymetallic mineralization are studied. The rescults show that, sericitization-muscovitization and chloritization are the mayor alteration types, followed by silicide and carbonatization in quartz-arsenopyrite-chalcopyrite stage(S1 stage),. While in the no-mineralization pyrite stage (S2 stage), pyritization become dominant, followed by sericitization, chloritization, silicide and carbonatization. In Lead-zinc polymetallic mineralization stage (S3 stage), the main alteration types are sericitization and chloritization, followed by carbonation, silicification, pyritization, and in the lead-zinc-silver carbonate stage(S4 stage), carbonatization become strong, followed by sericitization, chloritization and silicide. Geochemical study of the alteration rocks shows that intense pyritization is the main factor which caused Fe increase in altered wall rocks, which indicates that the ore-forming fluid is rich in Fe2+^{and S}2^-, and the mobility of Na, K and Ca in altered rocks is mainly due to the sericitization of K-feldspar, plagioclase and biotite, and the migration of Rb, Ba and Eu in altered rocks is related to sericitization, while Nb, Ta, Zr and Hf have no migration, mainly related to the stability of titanite and zircon. In conclusion, ore-forming fluid is magmatic original hydrothermal fluid, which is rich in alkali metal elements (Li, Cs、K), sulfur ore-forming elements Cu, Pb, zinc, Sb, Mo and Volatile ions (H+^,CO2, HS-^{, Cl}^-). In additon, the increase of pH, and the gradual decrease of K+^{and H}+^{, may be the main factors of precipitation of metallogenic elements such as zinc and lead.}
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Characteristics and Geochronology of Ductile Deformation in the Bayan Obo Ore District and Their Geological Significance

WANG Dongsheng, GAO Yupu, SHE Hongquan, ZHANG Li, LI Yike, GUO Bin, KE Changhui, YUAN Xingyu, MA Shouxian, ZHU Zeying, PENG Zidong

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The Bayan Obo deposit is the largest comprehensive Fe-REE-Nb deposit in the world. The shape of ore bodies and the texture of ore are closely related to ductile structures. To understand the deformation characteristics and evolution of ore structures in the ore district, this study collected rocks for microscopic and Th-Pb geochronological analysis based on macroscopic structural analysis. Results show that rhombic, banded, and folded ore structures can be identified in the Bayan Obo deposit, which reflects gradually strengthening ductile deformation, involving minerals such as magnetite, monazite, fluorite, rare earth minerals, and dolomite. The most widely developed banded structures represent the products of ductile deformation of rocks during the compression stage. Selected syntectonic monazite gives a Th-Pb age of 432 ± 4 Ma, belonging to the Early Paleozoic. Referring to previous geochronological results in the Bayan Obo deposit, it is believed that this age represents the ductile deformation occurs at the Middle Silurian. In addition, the coarse-grained monazite shows an age range of 477 to 838 Ma and the geological significance represented by these ages is not yet clear. It may be related to the alteration of monazite during the mineralization by hydrothermal activity, resulting in a certain degree of lead loss. The U-Pb age of zircon in the undeformed diorite-porphyrite dyke is 274 ± 4 Ma, which constrains the upper limit of ductile deformation. Combining regional geological results, it is suggested that the Middle Silurian ductile deformation in the Bayan Obo deposit corresponds to the collage between the North China plate and the Bainaimiao arc. The intense collision has transformed the original ore-forming structure from both macro- and microscopic aspects, forming the existing pattern.
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Study on quality evaluation method of typical vein quartz deposits in Dabieshan area

Xiao Ying, Deng Yufeng, Ma Jinhai, Shen Huanxi, Zhan Jianhua, He Zhenzhong, Zhu Chuanhai, Hao Wenjun

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The Dabieshan area in China is characterized by the widespread occurrences of Mesozoic metamorphism and magmatism, with abundant vein quartz resources, which may become one of the key regions for strategic mineral exploration of high-purity quartz (raw material) in China. This paper determines the quality grades of high-purity quartz vein quartz samples from the Hongjiawan mineral occurrence and Baishishan deposits in the Dabieshan area. A comparative analysis is conducted based on factors such as hand specimens, fluid inclusions, content and occurrence states of impurity element in the ores with different quality grades, to identify typical quality evaluation indicators for vein-quartz ores in the Dabieshan area. The content of SiO2 in the processed quartz sand from Hongjiawan and Baishishan vein-quartz ores can reach 99.9971% and 99.9968% respectively, which meets the quality requirements of middle and high-end products. The quality of the Hongjiawan ore is better than that of the Baishishan ore. The comparative study of different quality of high purity quartz raw materials shows that, if the vein quartz is snow-white in color, higher transparency, larger fluid inclusion sizes dominated by two-phase (liquid-vapor) primary fluid inclusions, and lower impurity elements content, the quartz has the greater probability of becoming high purity quartz raw materials. The contents of impurity elements in recrystallized quartz and core of quartz veins are generally low, thus we should pay more attention to this part of quartz. This conclusion has a significance for evaluating the potential resources of high purity quartz raw materials in this area and clarifying the geological characteristics of future prospecting targets.
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Characteristics of Lower Cretaceous Source Rocks and the favorable exploration target in Minle Basin of Hexi Corridor

Tianya, Bai Zhongkai, Yang Youxing, Du Zhili, Liu Lihong, Wu Jianwei

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The structural evolution, sedimentary characteristics and source rock characteristics of Minle Basin and Jiuquan Basin have certain similarities, but the exploration degree is very low, which is in the stage of regional exploration. In this paper, the Cretaceous source rock system is studied in Minle Basin. Through field outcrop, drilling sampling and sample analysis and testing, combined with geophysical data analysis, the geochemical and plane distribution characteristics of Cretaceous source rocks were clarified, and the potential analysis of oil and gas resources was carried out. The results show that : 1 Two sets of lacustrine dark gray, gray-black mudstone and shale are developed in the lower and upper Cretaceous formations in the Minle Basin, and the organic matter abundance of the two sets of source rocks reaches the standard of better continental source rocks. The organic matter type of the source rock is mainly type II. The maturity of the source rock in the lower rock group is high, and the lower part of the upper rock group reaches a mature state and has hydrocarbon generation potential. The source rocks of the lower rock group and the upper rock group are distributed in the three sags, and the closer to the center of the sub-sag, the greater the thickness of the source rocks. 3 The evaluation results of oil and gas prospect areasThe Yangfangxiang area in the southeast of Lizhaicun sag and the Laorenba area in the eastern margin of Zhangye sag are Class I prospective areas. The southern part of the Zhangye sag, the northern part of the Chaoyuansi sag, and the southern part of the Lizhaicun sag are Class II prospective areas ; the Sangongxia area in the southwest margin of the Zhangye sag and the Ganjunzhen area in the northwest margin of the Zhangye sag are Class III prospective areas.
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Apatite Fission Track Spatial Distribution Characteristics: Implications for the Evolution of Tectono-geomorphological Landscapes — A Case Study of Wugongshan

Gao Shangyan, Li Guangwei, Zhang Yuwei, Ye Zhanghuang

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The evolution of landforms is controlled by the interaction between tectonic activities and surface processes, and exploring the contribution of both to the evolution of structural geomorphology has always been a hot and difficult point in the study of the evolution of orogenic geomorphology. In recent years, the rapidly developing low-temperature thermochronology has become a powerful method for studying the quantitative evolution of tectonic geomorphology. Therefore, this study uses low-temperature thermochronology method to investigate the exhumation processes and mechanisms of the typical granite gneiss dome in China - Jiangxi Wugong Mountain. We targeted the core of the Wugong Mountain range - the north and south sections of Mingyue Mountain for sampling and conducted apatite fission track analysis. The apatite fission track ages are mainly concentrated at ~65-42 Ma, and the ages on both sides of the mountain show a clear negative correlation with elevation. This may be due to the fact that the exhumation of the Wugong Mountain dome in the Late Cretaceous were mainly controlled by the detachment faults on both sides, while the denudation process in the Cenozoic was mainly affected by surface erosion. This indicates that for relatively old orogenic belts, the spatial distribution characteristics of low-temperature thermochronology ages can be used as an indicator to discern the main control mechanisms of tectonic geomorphological evolution. In addition, according to our thermal history simulation results, the Wugong Mountain area has experienced a rapid exhumation stage in the Late Cretaceous, a slow stage from the Paleocene to the early Miocene, and a relatively rapid exhumation stage since the early Miocene, mainly controlled by regional tectonic activities and climate change, respectively.
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Evolution characteristics of marine nitrogen cycle and redox structure during early Cambrian in the western Hubei aulacogen of middle Yangtze Block

Meng Kang, Hu Yunpeng, Zhang Yu, Shao Deyong, Tang Lei, Song Hui, Zhang Tongwei

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The evolution characteristic of marine redox structure during early Cambrian in the western Hubei aulacogen of middle Yangtze Block is still unclear. In this study, the Lower Cambrian shales of well LX03 in the western Hubei aulacogen were taken as the research object. Firstly, origins of differences in nitrogen isotope compositions of whole rock and kerogen were analyzed to determine which nitrogen isotope was suitable for characterizing the marine redox environment at that time. On this basis, the dynamic evolution process of marine nitrogen cycle and redox structure during the deposition of Lower Cambrian Shuijingtuo organic-rich strata in this area was reconstructed by further integrating redox-sensitive elements and benthic foraminifera. The results showed that biological assimilation occurring in anoxic pore water during sedimentation and early diagenesis stages leaded to nitrogen isotope fractionation between kerogen and silicate minerals. However, this process took place within a relatively closed system and had minimal impact on the whole rock nitrogen isotope (δ15Nbulk). Moreover, the δ15Nbulk was not affected by secondary processes such as terrestrial input, microbial degradation, thermal maturation, and metamorphism, making it a reliable geochemical indicator for reconstructing the marine redox structure during the deposition of organic-rich sediments. During the deposition of the lower part of first member of Lower Cambrian Shuijingtuo Formation, the redox interface was located at the marine’s surface, with marine primarily characterized by euxinic condition (limited NO3- pool), and organisms acquired nitrogen mainly through nitrogen fixation. When the upper part of first member and lower part of second member of Lower Cambrian Shuijingtuo Formation deposited, the redox interface descended, with the upper oxic water expanded (enlarged NO3- pool), and organisms acquired nitrogen increasingly through the less energy-consuming NO3- assimilation process. During the deposition of the upper part of second member of Lower Cambrian Shuijingtuo Formation, the upper oxic water further expanded, and the bottom water transitioned to a low-oxygen environment. The low-oxygen bottom water promoted the proliferation of benthic foraminifera and other ancient organisms adapted to extreme low-oxygen conditions, with NO3- assimilation becoming the primary pathway for organisms to acquire nitrogen.
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The indicative significance of mica minerals to the genesis of Dangba pegmatite-type lithium deposit, western Sichuan, China

Zhao Yuan, Ran Fengqin, Tang Juxing, Peng Bo, Yang Yang, Han Jingrui, Feng Dabo, Bai Yun, Dai Yongkun, Tian Songlin

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Abstract:

Located in the Songpan-Ganzi orogenic belt, the Keeryin ore field is one of the important pegmatitetype lithium ore concentration areas in China. The Dangba deposit is a super-large pegmatite lithium deposit in the ore field. For a long time, it has been considered that the two-mica monzonitic granite in the Keeryin area is the main ore-forming parent rock of lithium mineralized pegmatite in this area. In order to further reveal the evolutionprocess of Dangba pegmatite and the enrichment mechanism of rare metals, mica, a penetrating mineral in granite and pegmatite, was selected as the research object in this paper. Based on previous studies, detailed rock and mineral identification, electron probe microanalysis (EPMA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis were carried out. The results show that: ①The mica series in the Keeryin two-mica monzonitic granite and Dangba pegmatite show the evolution trend of muscovite → iron-lithium mica → lithium mica, and 4AlTot?3SiIV+□VI and 3LiVI?AlVI+2□VI are the dominant substitution mechanism of this process; ② The muscovite series in the Keeryin two-mica monzonitic granite and Dangba pegmatite show theevolution trend of muscovite → iron-lithium mica→ lithium mica.The high degree of crystallization differentiation process of Dangba pegmatite, the initial melt rich in Li and the late fluid relatively poor in F, and the relatively weak scale of fluid action are of great significance for lithium mineralization.
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Sedimentary geochemistry of Mesozoic cherts in Tongjiang area of Northeast China: Implication on the subduction of Paleo-Pacific subduction

ZHANGWenHao, ZHOU Jianbo, ZHOU Xingui, WANG Dandan, LIU Weibin, Meng Yuanlin, LIU Xufeng

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Abstract:

The Sanjiang area in Northeast China hosts the sole exposed Mesozoic siliceous rock series in northern China, which holds significant geochemical characteristics for unraveling its genesis and tectonic setting, particularly to trace the temporal and spatial initiation of paleo-Pacific subduction. In the Tongjiang area north of Sanjiang, the "Heitongdi 1 Well" reveals a silicic rock system from the late Triassic to Early Jurassic Dajiashan Formation, spanning approximately 400 meters. Through field geological investigation, microscopic observation, and petrogeochemical analysis of core samples from this well, we have conducted a comprehensive study on the origin and tectonic environment of these siliceous rocks. Radiolarian fossils are observed in the siliceous rocks of the Tongjiang area. The mean Al/(Al+Fe+Mn) value in the siliceous rock samples was 0.74, with no discernible Ce anomaly and Ce/Ce* values ranging from 1.02 to 1.54, (La/Ce)_SN≈1, no significant difference in Y/Ho values, a mean Y/Ho value of 30.02, and a mean Eu/Eu* value of 1.17, indicating that these siliceous rocks were formed in a continental margin island arc environment. The present study also provides compelling evidence for the initiation of subduction of the Paleo-Pacific plate beneath the Eurasian plate during the late Triassic period, leading to the establishment of an island arc environment along the eastern margin of Jiamusi Block. The inferred location of the subduction suture between these two plates is situated westward from Tongjiang drilling hole.
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Ordered distribution and reservoir characteristics of Lower Permian sedimentary rocks in Junggar Basin

Zheng Menglin, Wangran, Chang Qiusheng, Qin Zhijun, Wang Tao, He Wenjun, Guo huajun, Zou Yang, Sun Jing, Wu Haisheng, Shan Xiang

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Mahu Sag is an important example of the application of the theory of the whole oil and gas system, Junggar Basin. The oil-gas reservoir pattern with normal and irregular distribution corresponds to the reservoir type with orderly distribution. In order to clarify its reservoir characteristics and control factors, the drilling, logging, analysis and laboratory analysis data of more than 50 Permian reservoirs in Mahu Sag are analyzed. The Permian sedimentary rock reservoirs in Mahu Sag are characterized by orderly lithology, facies and reservoir property from the edge of the sag to the depositional center. The lithology develops coarse clastic rocks, medium clastic rocks and fine-grained sedimentary rocks successively, and the grain size changes from coarse to fine in an orderly, continuous and sequential manner, which corresponds to the sedimentary facies changes. Coarse clastic rocks can be divided into rich shale conglomerate facies, shale conglomerate facies and lean shale conglomerate facies according to the level of shale content. Fine-grained sedimentary rocks can be divided into argillaceous lithofacies and dolomitic lithofacies according to the content of felsic and livid. The lean and argillaceous conglomerate facies and argillaceous rock facies have good reservoir property, and large-scale conventional conglomerate and unconventional shale oil reservoirs have been found respectively. Sedimentary facies control the orderly distribution of lithology, and gravity flow, torrent, traction flow, heavy flow and light flow dynamic fluid are closely related to the orderly distribution of lithofacies. The content of argillaceous complex and the composition of felsic mineral have decisive influence on the reservoir property of coarse clastic rock and fine grained sedimentary rock, respectively, and compaction diagenesis has important influence on the reservoir property of medium clastic rock. The orderly distribution of sedimentary rocks and the regularity of their reservoir properties control the gradual transition of oil and gas from continuous unconventional reservoirs to discontinuous conventional reservoirs.
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Sequence-Stratigraphy-Filling and Reservoir-Cap rock Assemblage Distribution Under the Control of Lake Basin Types: A Case Study of the Fengcheng and Baikouquan Formations in the Mahu Sag, Junggar Basin

zhangbao, Yan Detian, Tongyong, Zheng Menglin, Chang Qiusheng, Wei Xiaosong, Zhang Lei, Bai Yu, Yu xing

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Abstract:

The Junggar Basin, as one of China's important oil and gas production areas, contains abundant petroleum reserves. However, research on the basin's lake basin evolution is relatively limited, particularly regarding the relationship between lake basin types and the distribution of reservoir-cap rock assemblage during the Permian to Triassic deposition.This study, based on sequence stratigraphy frameworks, integrates structural evolution and paleoclimatic characteristics to systematically analyze the control of lake basin types on sequence-stratigraphy-filling and the distribution of reservoir-cap rock assemblage in the Junggar Basin. The results show that the Permian-Triassic sequence in the northwestern margin of the Junggar Basin has been divided into three supersequence (SSQ1-SSQ3) and eight third-order sequences (SQ1-SQ8). SQ2 is subdivided into the rift initiation system tract, rift climax system tract, and post-rift system tract. SQ6 is subdivided into the falling-stage systems tract, the lowstand system tract, expansion system tract, and the highstand system tract. The deposition period of SQ2 characterizes a typical underfilled discharge (UF-D) lake basin, where high-quality reservoirs mainly develop in the rift climax system tract, characterized by conglomerates and sandstones with residual intergranular pores and dissolution pores, resulting in relatively high porosity. The source rocks exhibit high productivity, conditions of high anoxic preservation, and weak dilution. The distribution of the Fengcheng Formation's reservoirs and source rocks is controlled by fault activities accompanied by the input of hydrothermal fluids and arid conditions induced by the Late Paleozoic glaciation.During the SQ6 deposition period, a typical overfilled lake basin is represented, with high-quality reservoirs mainly developing in the forced regressive and lake expansion system tracts, primarily consisting of sandstones. Continuous lake wave reworking and intermittent exposure increased porosity. The primary source of hydrocarbons is the SQ5 source rock, characterized by high productivity, poor preservation conditions, and strong dilution. The distribution of the Baikouquan Formation's reservoirs is controlled by tectonic uplift during the late Hercynian orogeny, the arid paleoclimate conditions of the Permian-Triassic transition, and the subsequent continuous lake transgression. This study reveals the sedimentary evolution patterns of the Permian to Triassic strata in the northwestern Junggar Basin, particularly the sequence-stratigraphy-filling characteristics and reservoir-cap rock assemblage distribution controlled by lake basin types. The findings provide important references for the study of lake basins with similar structural and climatic settings and have significant implications for oil and gas exploration.
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Permian paleogeographic differentiation evolution and platform margin model comparison in Sichuan Basin

Li Wen, Chen Anqing, Zhang Xihua, Sun Shi, Huang Huiwen, Gao Zhaolong, Xu Shenglin, Huang Ganghui, Xie Hao, Yang Shuai, Chen Hongde

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Abstract:

The carbonate platform margin is an important gathering place of large-scale oil and gas resources, and the study of paleogeographic differentiation is the basis to reveal the characteristics and development laws of the carbonate platform margin. Following the discovery of a trillion square meter natural gas gold accumulation zone in the platform margin reef-beach facies of the Upper Permian Changxing Formation in Sichuan Basin, the platform margin beach reservoir of the Middle Permian Maokou Formation has recently been discovered, and several open flow wells of more than one million square meters have shown great exploration potential. However, there are significant differences in sedimentary filling and reservoir characteristics between these two periods, and detailed comparative analysis will help deepen the understanding of carbonate platform model and its reservoir control effect. Based on a large number of drilling, field outcrop and seismic data from the Sichuan Basin and its surrounding Permian system, the typical sedimentary facies and lithofacies paleogeographic pattern are analyzed, and the differences between the two types of platform margins are compared. The results show the differentiation from shallow-water platform to deep water shelf by multiple synsedimentary faults occurred in Permian paleogeography of Sichuan Basin from Maokou period, with Kaijiang-Liangping trough being the most typical. The shallow-water carbonate platform of Changxing Formation is characterized by the development of thick platform margin reef-beach facies, and the shallow-water carbonate platform of Maokou Formation is characterized by the development of thin platform margin beach facies, both of which rapidly change into siliceous rock and carbonaceous shale. The Maokou period belongs to the initial geomorphic inherited platform margin, which is represented by several thin beach bodies with intermittent accretion under the background of wide margin. In the Changxing period, the platform margin was shaped by sedimentary border, showing a thick reef flat body with continuous accretion or prograding under the background of narrow margin. In general, both platform margins have the potential to develop large-scale reservoirs and are important targets for exploration of large oil and gas accumulation zones.
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Provenance characteristics of the Yangjiazhuang Formation on Tianheng Island: constraints from detrital zircon U-Pb dating and whole-rock geochemistry

MENG Yuanku, Yang Shubo, Yang Peng, Meng Fanxue, Lu Jie, Gao Cunshan, Li Zhaoying, Wang Zhenzhen

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Abstract:

The Jiaolai basin was formed in the rapid exhumation processes of the Sulu orogenic belt and Jiaobei terrane. Its evolutionary processes played a key role in constraining exhumation and denudation of the Sulu orogenic belt and Jiaobei terrane and destruction of the north China Craton (NCC). In this work, we took the Yangjiazhuang Formation of the Laiyang Group, which is located in the eastern margin of the Jiaolai Basin, as the research target to carry out systematic field geological survey, petrographic analyses, detrital zircon U-Pb dating and whole rock element measurements. Based on the systematic studies on the Yangjiazhuang Formation, we can draw the following conclusions: (1) the sedimentary age of the Yangjiazhuang Formation is well-defined between 125 and 115 Ma, belonging to the Apian stage of the Early Cretaceous; (2) the geochemical features of the mudstone revealed that provenance of the Yangjiazhuang Formation experienced relatively weak chemical weathering, and primary sedimentation played a key role, and the upper continental crustal (UCC) materials were the dominant provenance; (3) change of the sedimentary provenance of the Yangjiazhuang Formation and diversities indicated that the Jiaobei terrane was the other important provenance during the middle-late stages of sedimentaion besides the Sulu orogenic belt. Combined with the regional tectonic background, we propose that the rapid uplift and exhumation of the Sulu orogenic belt and Jiaobei terrane might have a close relationship with the crustal large-scale extension and thinning due to the destruction of the NCC.
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The indicators of Muscovite and Feldspar to the Prospecting direction of Rare metal pegmatite——Constraint on the discovery of spodumene pegmatite in Yanlingguan, xintai city, central Shandong

LIU Qinlong, LI Jiankang, LI Peng, LI Yingjie, LI Shenghu

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Abstract:

The efficient prospecting and exploration indicators of rare metal pegmatite in the eastern high coverage area is still difficult. In order to study how to delineate the mineralized pegmatite in the rare metal pegmatite in the eastern high coverage area, this studies carried out the major and trace elements of muscovite and feldspar in Yanlingguan pegmatite group in Xintai city, Shandong Province, analyzed and delineated the favorable areas of rare metal pegmatite, determined the prospecting direction by using the elemental composition and mineralization index of muscovite and feldspar, successfully found lepidolite and spodumene, and calculated the crystallization temperature of Yanlingguan pegmatite group by using feldspar thermometer. The regional zonation of Yanlingguan pegmatite group is poor, with no obvious change in lithology and mineral composition. It can be divided into Taohuayu area in the south, Tianjingyu area in the middle and Yanlingguan area in the north. The K/Rb ratio and Li of mica and feldspar show that the pegmatite dikes in Yanlingguan area have undergone highly crystalline differentiation and evolution. The conclusion that Li-rich muscovite and Cs-rich feldspar can be used as indicator minerals for lithium mineralization in the eastern high coverage area is confirmed. According to the calculation of feldspar temperature, the temperature changes are very regular when the trondhjemite in Shanggang unit and Yanlingguan pegmatite field crystallize, so the trondhjemite is the ore-forming parent rock of Yanlingguan pegmatite field.
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Meso-Cenozoic tectonic evolution and geomorphologic restoration of the west section of Bonan low uplift, Bohai Bay Basin

Wu Zihan, Hu Zhiwei, Shi Panpan, Dai Liming, Li Sanzhong, Li Fakun, Wang Zhuo, Hu Zihao

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Abstract:

The west section of Bonan low uplift in the Bohai Bay Basin has been found to have great characteristics of medium-deep buried-hill type oil and gas trap in recent exploration work, and internally discovered the Bozhong 26-6 large-scale oil and gas reservoir. Discussions on the formation and evolution of buried-hills, the development sedimentary systems, and the mechanisms of oil and gas generation, storage and migration often require tectonic analysis and tectonic geomorphological restoration work. Therefore, to reveal the complete tectonic deformation and geomorphic evolution of the west section of Bonan low uplift, and to provide theoretical support for oil and gas exploration, this paper, based on the reflection seismic and drilling data in the study area, detailed the strata distribution and tectonic deformation characteristics during Mesozoic-Cenozoic, and used Move software to conduct two and three dimensional tectonic restoration, accurately restoring the geomorphological features during the major periods of tectonic activity. Results reveal that: (1) During the early Mesozoic (from the Indosinian to the early Yanshanian), under the strong compressional orogeny transitioning from a near S-N to NE direction, the study area developed a numerous near E-W and NE directed thrusts, as well as several near S-N strike slip faults. The region experienced intensive uplift, with the overall lack of the Jurassic sedimentation and extensive erosion of the Paleozoic strata. The Precambrian basement was exposed and flattened, presenting a large-scale flattened mountain landform. (2) During the late Mesozoic (from middle to late Yanshanian), under a strong NW-SE directed extensional environment, the reverse faults in the Huanghekou Depression on the south side of the uplift experienced intense negative inversion activity. This allowed the depression to receive a large amount of Cretaceous volcaniclastic and muddy-sandy sediments. The west section of Bonan low uplift and part of the Bozhong Depression on the north side still exhibit uplifted landforms and serve as sediment source areas. (3) During the early Cenozoic (from early to middle Himalayan), under the strong NW-SE directed extensional and rift environment, the study area experienced near S-N directed bidirectional detachment activity. The Huanghekou Depression continued to experience southward faulting, forming a basket-shaped and half-graben shaped structure. The strata in the Bozhong Depression underwent northward faulting and detachment. The west section of Bonan low uplift was affected by transtensional detachment, presenting a geomorphic feature of “high and narrow in the west, low and wide in the east”, ultimately forming the current tectonic pattern of “two depressions with one uplift”, providing space for the deposition of Cenozoic Shahejie Formation source rocks and Dongying Formation cap rocks.
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Zirconium resources and mineralization in China

CHEN Binghan, YU Jinjie, YAO Fojun

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Abstract:

This article divides China's zirconium deposits into alkaline granite type, alkaline complex type, pegmatite type, weathering crust residual slope deposit type, coastal sedimentary type, and river alluvial type. The predicted types of zirconium deposits are divided into the granite type, pegmatite type, coastal sedimentary type, river alluvial type, weathered crust and residual slope deposit type. China's zirconium ore resources are distributed in 15 provinces (autonomous regions) including Inner Mongolia, Hainan, Sichuan, and Guangdong, with zirconium ore reserves in these four provinces (autonomous regions) accounting for 93.7% of the national total. Based on the statistics, the metallogenic period of zirconium deposits in China is divided into Neoproterozoic, Late Paleozoic, Mesozoic, and Cenozoic. 14 zirconium metallogenic belts are divided. 34 Zirconium-related metallogenic series are determined and the metallogenic pedigree of zirconium deposits in China is established. The coastal sedimentary and river alluvial zirconium deposits along the southeast coast can be used as prospects for zirconium exploration.
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Mineralogical and geochemical characteristics and enrichment mecha-nisms of critical elements in the No. 3 coal seam of the Shanxi Formation in the Hengcheng mining area, Ningdong coalfield

GUO Yajie, SHI Yutao, JI Xiaoyan, MA Shaodong, HUANG Pengcheng, YANG Dequan, CAO Yongbin, SUN Jia, ZHANG Qi, LI Baoqing

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Abstract:

The study of coal-related critical elements deposits has become a frontier hotspot in coal geology research and an important source for increasing reserves of critical elements mineral resources. This study focuses on the No. 3 coal seam of the Early Permian Shanxi Formation at the Maliantai Coal Mine in the Hengcheng mining area of the Ningdong coalfield. It investigates the mineral composition and geochemistry to determine the distribution, occurrence, and en-richment characteristics of elements minerals in the coal, as well as to evaluate their compre-hensive utilization. The study results show that:（1）The No. 3 coal seam at Maliantai is characterized by medium ash yield, high volatile yield, ultra-low total moisture content, and low to medium total sulfur content, with minerals in the coal mainly composed of kaolinite；（2）The major elements in the coal are primarily composed of SiO2 and Al2O3, with minor amounts of Fe2O3, CaO, and MgO. Compared to the average coal worldwide, Li and Zr reach enrichment levels, while Ga, Nb, Hf, Ta, Pb, Th, and rare earth elements (REE+Y) are slightly enriched；（3）Li and Ga are mainly found in kaolinite, Zr (Hf) and Nb (Ta) are primarily found in zircon, and REY is primarily hosted in kaolinite and aluminum phosphate (goyazite) associated with kao-linite. The Yinshan ancient land in the northeast of Ningdong coal field provides important felsic clastic material for the Malitai No. 3 coal, in addition, the Alashan block also provides some volcanic clastic material. The enrichment of critical metals such as Li, Zr (Hf), and Nb (Ta) in the coal is mainly controlled by the input of alkaline-peralkaline felsic clastic materials, with chemical weathering and water-rock interactions being secondary controlling factors. The en-richment of Ga is primarily controlled by the intensity of chemical weathering. The enrichment of REY is mainly influenced by the input of clastic materials and water-rock interaction processes. In addition, the kaolinite content also plays a role in the enrichment of Li, Ga, and REY. Malian Tai No. 3 coal has potential as a source of Li-Ga-Zr-REY metals.
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Time limit of Mesozoic and Cenozoic uplift in the eastern margin of Yinchuan graben：evidence from fission track

Wang ShiZhe, Zhao HongGe, Liu ChiYang, Zhang YiCheng, Wang JianQiang, Wang Jian, Ma Biao, Li Xingcheng

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Abstract:

The eastern margin of Yinchuan Graben is located in the northern part of the structural belt on the western margin of Ordos Basin, at the junction of Alashan Block, Ordos Block and Qinqi Fold Belt with strong activity. The Mesozoic and Cenozoic have experienced multi-stage structural activities, and its structural uplift is of great significance to the study of structural evolution and oil and gas exploration in the surrounding areas. Based on the age, length characteristics and thermal history simulation analysis of apatite and zircon fission tracks in different areas and horizons in the eastern margin of Yinchuan Graben, combined with structural characteristics and stratigraphic contact relationship, this paper points out that the study area has experienced at least Late Jurassic (160~145Ma), Late Cretaceous (100~70Ma), Early Miocene (22~20Ma) and Late Miocene (10~8Ma). There are some differences in uplift characteristics in different periods and regions. The uplift in the northern and southern parts of Mesozoic started earlier (early/middle Jurassic), and it gradually uplifted from the north and south parts to the middle part. The uplift rate in the middle part of late Jurassic was higher than that in the north and south parts, and the whole uplift was slow in the late Cretaceous. Since Miocene, the uplift has been characterized by early south and late north, and the uplift rate increased northward. This uplift period and differential uplift characteristics have corresponding geological response and regional dynamic mechanism.
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Genetic relationship of the deposit in Qibaoshan ore-concentration area of Wulian County, Southern Margin of Jiaolai Basin: Constraints of in-situ sulfur isotope and trace element of sulfides

Tang Mingying, Ding Zhengjiang, Zhan Honglei, Zhu Wei, Wang Xin, Wei T, Li Fuhua, Chen Jian, Zou Zhanchun

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The Au-Cu polymetallic deposits represented by the Qibaoshan ore-concentration area of Wulian county is developed in the Southern Margin of Jiaolai Basin, three typical deposits are developed, namely, Jinxiantou Au-Cu deposit, Diaoyutai pyrite deposit and Qibaoshan Pb-Zn polymetallic deposit. In order to further elucidate the genetic relationship between ore deposits, improve the study of ore-forming system in ore concentration area, and establish the ore-forming model of ore deposits, the main sulfides in the ore deposit were tested and analyzed in situ for sulfur isotopes and trace elements of pyrite.. The sulfides in the Qibaoshan ore concentration area has a relatively concentrated sulfur isotope peak distribution range (0‰ ~ 6‰), which comes from the same or similar deep magmatic system.. The Cu, Zn, As, Se, Ag, Sb, Pb and Bi in pyrite show relatively regular changes from Jinxiantou Au-Cu deposit to Diaoyutai pyrite and then to Qibaoshan Ag-Pb-Zn polymetallic deposit, The distribution characteristics of elements show that the ore-forming fluid as a whole presents an evolution process from magmatic hydrothermal to mixed hydrothermal. Comprehensive analysis shows that the deposits in Qibaoshan ore collection area are closely related in time and space. The deposits are the products of the same geological and tectonic environment and different parts of rock construction, which together constitute the porphyry-epithermal Au-Cu-Pb-Zn-Ag polymetallic metallogenic system in Qibaoshan area.
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Evolution and genetic mechanism of high pressure in the Qianfoya Formation shale gas in the Puguang East syncline in northeastern Sichuan

zhaoniubin, lilingxi, wantao, wanggonghuai, jinda, houxianbo, zhanghao

Abstract: (128)</

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Volume 99,2025 Issue 11

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