Geoscience

Lithosphere Breakup Process and Stratigraphie Architecture Patterns in the Passive Marginal Basin

TIAN Naxin, XIE Xinong, LI Jun, YU Xiaohang, YANG Guangqing

2025, 39(04): 857-870. DOI: 10.19657/j.geoscience.1000-8527.2025.034

Asbtract ( 82 )

HTML ( 9)

PDF (8530KB) ( 45 )

Figures and Tables | References | Related Articles | Metrics

The coupling relationship between the deep structure of the lithosphere and passive continental margin sedimentary filling is a key scie.pngic issue in basin dynamics research. Taking the Pearl River Mouth Basin in the South China Sea and the passive margins of the North Atlantic as examples,this study reveals the characteristics and formation patterns of sedimentary infill in magma-poor and magma-rich continental margins through integrated analysis of the coupling between deep crustal deformation and basin infill in passive margins, based on the non-transient lithospheric breakup process.The results show that the lithospheric rupture process undergoes four stages: stretching, thinning, exhumation, and rupture. Spatially, from land to ocean, the tectonic units can be divided from land to ocean into the proximal zone, necking zone, distal zone, and oceanic-continental transition zone.In the early stretching stage, it is characterized by high-angle normal faults and isolated faulted depressions. During the necking and exhumation stages, lithospheric extensional deformation gradually migrates seaward, with low-angle detachment faults as the main feature. In the later stage, the main extension is concentrated in the mid-ocean ridge area, while the passive margin region undergoes regional thermal subsidence.Therefore, the stratigraphic framework patterns of passive marginsbased on the non-transient lithospheric rupture processare of great significance for oil and gas exploration in passive margin basins.

Deformation and Activity Characteristics of Strike-slip Fault Zones in the Western Shunbei Area, Tarim Basin

HUANG Cheng, LIN Bo, YU Yixin, YANG Fan, YU Lang, CHEN Junyu, NIU Yuemeng

2025, 39(04): 871-883. DOI: 10.19657/j.geoscience.1000-8527.2025.030

Asbtract ( 56 )

HTML ( 1)

PDF (17058KB) ( 31 )

Figures and Tables | References | Related Articles | Metrics

Several NNW-trending strike-slip faults are developed well in the area west of the Shunbei No.5 Fault Zone in the Tarim basin, which have controlled hydrocarbon accumulation in the Ordovician carbonate rocks.However, research on the development characteristics and formation mechanisms of these strike-slip fault zones remains limited.Based on the refined interpretation results of the latest 3D seismic data, the paper analyzes the characteristics of differential deformation of the strike-slip fault zones in the western Shunbei area, clarifies the activity periods and intensities of the strike-slip faults, and investigates their formation mechanisms in the context of regional orogenic events along the basin margin.The strike-slip fault zones in the western Shunbei area extend downward into the Precambrian and upward to the Permian. In cross-section, they mostly present as single upright faults, flower structures, and graben morphologies. On the plane, the strike-slip fault zones are mainly distributed in a NNW-trending linear and en-echelon pattern, with overlapping segments developed in local areas. The strike-slip fault zones mainly undergo right-lateral strike-slip movement, and the activity intensity of the fault zones gradually diminishes eastward.The strike-slip fault zones in the western Shunbei area have mainly gone through four evolutionary stages: the initial weak strike-slip stage in the Early Caledonian, the strong strike-slip stage in the Middle Caledonian, the weak strike-slip stage from the Late Caledonian to the Early Hercynian, and the continuous weak strike-slip stage from the Middle to the Late Hercynian.By analyzing the differential orogenic activities on the basin margin of the Tarim Basin and the characteristics of the regional stress field, it is pointed out that pre-existing shear fractures serve as the basis for the formation of the NNW-trending strike-slip fault zones in the western Shunbei area. Moreover, multi-stage adjustment deformation, oblique compression, and intra-plate block rotation also exert important influences on the development of the strike-slip fault zones.

Characteristics of Permian Strike-slip Faults in Central Sichuan Basin and Their Significance for Hydrocarbon Accumulation

TANG Hao, WU Guanghui, MA Bingshan, HUANG Tianjun, ZOU Yu, LAN Xuemei, SU Chen, WANG Jiamu

2025, 39(04): 884-897. DOI: 10.19657/j.geoscience.1000-8527.2025.017

Asbtract ( 50 )

HTML ( 6)

PDF (15345KB) ( 39 )

Figures and Tables | References | Related Articles | Metrics

Recent studies have revealed the presence of large-scale strike-slip faults in the central Sichuan area within the Sichuan Cratonic Basin, which makes it a promising new region for the exploration and development of fault-controlled oil and gas reservoirs. Drilling results indicate that a series of high-yield wells in the Permian of the Gaomo area in central Sichuan bear a certain spatiotemporal correlation with the distribution of strike-slip faults, confirming a close relationship between strike-slip faults and gas reservoirs. However, the characteristics of strike-slip faults and their interaction with gas reservoirs remain unclear, hindering the exploration and development of gas reservoirs in the central Sichuan area.Based on 7,066 km² of contiguous 3D seismic data and typical well data from the Gaomo area, this study analyzes the basic characteristics of weak strike-slip faults in the Permian and their controlling effect on gas reservoirs, providing a case study for research on fault-related hydrocarbon accumulation under weak strike-slip fault activity.The results show that there are eight first-order strike-slip faults developed in the Permian of the Gaomo area, with strikes of NEE, EW, and NW, and lengths ranging from 30 to 160 km. The spacing between first-order strike-slip faults is 10 to 30 km, and the Permian strike-slip faults are basically inherited from the Cambrian faults. Statistical analysis of the throw of the 8 major strike-slip faults suggests weak activity. The activity intensity of the Permian strike-slip faults in central Sichuan exhibits regional differences, with an overall pattern of being stronger in the north than in the south and stronger in the east than in the west. Both the distribution and intensity of strike-slip faults at the base of the Lower Permian are greater than those at the base of the Upper Permian.The Permian strike-slip faults may have undergone left-lateral extensional-tensional activity controlled by the Emei Taphrogenesis. The Permian strike-slip faults in the Gaomo area display obvious segmentation, with structural styles mainly being simple ones such as en echelon, linear, and oblique. The segmentation of strike-slip faults leads to differences in fault structural characteristics and petrophysical properties of fault zones, exerting a significant impact on fault permeability and hydrocarbon migration and accumulation. Logging results show that within 2 km of the core of a single well’s strike-slip fault, porosity and permeability tend to improve significantly, which may be controlled by the fracture network of the strike-slip fault. A series of drilling data indicates that the closer to the strike-slip fault, the higher the hydrocarbon production, confirming the controlling effect of strike-slip faults on hydrocarbons.Anatomical analysis of single-well gas reservoirs confirms that strike-slip faults have three types of favorable hydrocarbon accumulation effects and two types of destructive effects on accumulation. Fault-lithology binary hydrocarbon accumulation is the main development model of Permian gas reservoirs. The favorable strike-slip fault-related accumulation models include vertical connection between faults and source rocks, vertical migration and accumulation through faults with upward migration pathways, and bilateral clamping by faults with bidirectional migration pathways. However, multi-stage faulting activities of strike-slip faults may directly damage oil and gas, and the structural characteristics of strike-slip faults-small throws in the deep part and large throws in the shallow part-also have a destructive effect on hydrocarbon accumulation.

Fluvial Geomorphological Characteristics and Their Relationship with Tectonic Activity in the Babianjiang Fault Zone, Southwest Yunnan

TIAN Peng, ZHOU Qingyun, BAI Xianfu, LUO Weidong, LIU Jingnan

2025, 39(04): 898-907. DOI: 10.19657/j.geoscience.1000-8527.2024.129

Asbtract ( 42 )

HTML ( 3)

PDF (6995KB) ( 19 )

Figures and Tables | References | Related Articles | Metrics

The Babianjiang Fault is located in a seismically active region of southwestern Yunnan. As a non-boundary fault with no historical records of major earthquakes, its tectonic activity remains poorly understood. Based on field investigations, this study extracts topographic parameters and hypsometric integral (HI) values of drainage basins in the Babianjiang Fault Zone using a digital elevation model (DEM). It aims to explore the dominant factors controlling regional topography and geomorphology, and quantitatively analyze the relationship between fluvial geomorphic characteristics and tectonic activity in the Babianjiang Fault Zone. The results indicate that tectonic activity is the primary control on regional geomorphic features. Spatial variations in topographic relief and HI values reveal significant along-strike segmentation in the fault’s tectonic activity: the northern segment is more active, whereas the central segment is relatively weaker. Notably, HI values across the fault show an “east-high, west-low” asymmetric pattern, suggesting that the eastern block has experienced relative tectonic uplift compared to the western block-indicating reverse faulting activity. This study concludes that the Babianjiang Fault is primarily characterized by reverse faulting with a dextral strike-slip component, and geomorphic parameters clearly respond to its tectonic activity.

Research on Key Issues of Stability of Typical Dangerous Rock Masses in the Changxing Formation, Guizhou Province

QIN Hongliang, ZHAO Cui, ZHU Yuhua, HU Rong, WU Bo, HUANG Xinxin, HUANG Guangcai

2025, 39(04): 908-919. DOI: 10.19657/j.geoscience.1000-8527.2025.035

Asbtract ( 51 )

HTML ( 2)

PDF (8045KB) ( 17 )

Figures and Tables | References | Related Articles | Metrics

For a long time, key issues such as the formation mechanism of dangerous rock masses, the possibility of collapse, main triggering factors, and the impact range of collapse have not been effectively solved. This study takes typical dangerous rock masses in the Changxing Formation of Guizhou as the research object, and systematically investigates their formation mechanism, stability, and impact range by comprehensively applying methods including field investigation, engineering survey, rock mechanics test, mathematical statistics, stereographic projection, limit equilibrium method, numerical simulation, and correlation analysis. The results show that the formation mechanism of dangerous rock masses in this area is as follows: the hard limestone of the Changxing Formation forms steep cliff landforms, and fractures are generated under the action of various combined forces; the lithological combination of “hard on top and soft at the bottom” forms concave rock cavities at the bottom of cherty limestone in the Changxing Formation, thus forming dangerous rock masses at the free face of surface cliffs. The conclusions of quantitative calculation and qualitative analysis of dangerous rock mass stability are basically consistent: 3 individual dangerous rock masses are in a sub-stable state, and 3 are in a basically stable state. The maximum impact distance of dangerous rock mass collapse is 345 m, and the rockfall impact range is about 0.36 km?. The study indicates that the dangerous rock masses in the study area mainly result from the combined action of factors such as rock strength, chemical composition, internal and external forces, and characteristics of stratigraphic-lithological combinations. Within the time scale of several decades of human lifespan, the overturning moment stems from water pressure, and rainfall is the most important triggering factor for toppling collapses in this area. The collapse travel distance and total kinetic energy are positively correlated with the volume of rockfall blocks, respectively, while the bounce height has no correlation with the volume of rockfall blocks. This research has certain scientific guiding significance for the prevention and control of similar dangerous rock mass disasters in karst mountainous areas of Guizhou.

LA-ICP-MS In-Situ U-Pb Ages of Uraninite from the Dafuling Uranium Deposit, Eastern Hunan, and Its Implications for Ore Genesis

FAN Pengfei, SHEN Xikun, HUANG Guangwen, LI Mangen, GU Yong, WANG Ke, LIU Tao, GUO Yeda

2025, 39(04): 920-930. DOI: 10.19657/j.geoscience.1000-8527.2024.028

Asbtract ( 51 )

HTML ( 4)

PDF (6304KB) ( 15 )

Figures and Tables | References | Related Articles | Metrics

The Dafuling Uranium Deposit is part of the Mingyuefeng Ore Field in eastern Hunan, and it represents a newly proven perigranitic uranium deposit within this ore concentration area. Recent prospecting and exploration practices have shown that the deposit exhibits significant uranium mineralization scale and considerable prospecting potential. However, due to the insufficient analysis of the characteristics of uranium minerals in this deposit and the weak constraints on the timing of uranium mineralization, the understanding of the ore deposit’s genesis has been somewhat hindered. Against this backdrop, this study conducted detailed field geological surveys, collected representative uranium ore samples, and employed laboratory ore-mineral identification, scanning electron microscopy (SEM), electron probe microanalysis (EPMA), and LA-ICP-MS, among other analytical techniques. For the first time, it deciphered the characteristics of uranium minerals in the deposit and constrained their metallogenic age. The results indicate that the exposed uranium mineral in the deposit is mainly uraninite, with a uranium metallogenic age of approximately 70 Ma, corresponding to the late Cretaceous. Combined with the tectonic setting, it is preliminarily considered that the mineralization is closely related to the Mesozoic (75-70 Ma) lithospheric extension and thinning event in South China, indirectly indicating that the Dafuling Uranium Deposit might have formed in a tectonodynamic setting of lithospheric extension and thinning.

Characteristics of Ore-Forming Fluids and Physicochemical Conditions for Ge Enrichment in the Wusihe Lead-Zinc Deposit, Sichuan

SUN Shiqiang, CHEN Cuihua, LAI Xiang, GU Ying, ZHAO Wenhao, ZHANG Haijun, MA Tianqi, CHEN Xiaojie, SONG Zhijiao

2025, 39(04): 931-946. DOI: 10.19657/j.geoscience.1000-8527.2025.021

Asbtract ( 56 )

HTML ( 1)

PDF (13451KB) ( 33 )

Figures and Tables | References | Related Articles | Metrics

The large-scale Wusihe lead-zinc deposit is a typical Ge-rich lead-zinc deposit in the Sichuan-Yunnan-Guizhou Metallogenic Belt.Although extensive prior research has been conducted on the characteristics of ore-forming fluids, as well as the occurrence and substitution mechanisms of Ge, the key physicochemical conditions controlling Ge enrichment remain unclear, which hinders a comprehensive understanding of its enrichment mechanisms. To address this, we performed petrological and mineralogical analyses, LA-ICP-MS analyses, and microthermometric analysis of fluid inclusions to systematically investigate the ore-forming fluids and Ge enrichment conditions of this deposit.Two stages of sphalerite development are identified in the deposit, corresponding to two mineralization stages: (Ⅰ) the quartz-sphalerite-pyrite-galena stage and (Ⅱ) the galena-pyrite-sphalerite-asphalt stage. LA-ICP-MS results show that the average Ge content in sphalerite from StageⅠis 221.0×10-6, which is higher than that from StageⅡ(72.9×10^-6). Microthermometric data of fluid inclusions indicate that the homogenization temperatures during the hydrothermal stages average 220 ℃ (StageⅠ) and 180 ℃(StageⅡ), respectively. The pH values of the two stages are comparable, with little variation. The average salinities, expressed as w(NaCl_eq), are 8.0% for StageⅠand 5.9% for Stage Ⅱ, indicating that the ore-forming fluids are of medium-low temperature and medium-low salinity. The ore-forming pressures are 43×10⁵-283×10⁵ Pa for StageⅠand 120×10⁵-236×10⁵ Pa for Stage Ⅱ.Based on the Ge enrichment patterns, its occurrence, ore-forming fluid characteristics, and thermodynamic phase diagram calculations, the Ge enrichment conditions in sphalerite are determined as follows: for StageⅠ, log $f O 2$ ≤-40.40, -15.75≤f_S2≤-4.71, log[Zn]≥-14.36, and log[Ge]≥-26.44; for StageⅡ, log $f O 2$ ≤-44.28, -18.64≤log $f S 2$ ≤-5.78, log[Zn]≥-14.84, and log[Ge]≥-28.19.The study suggests that sulfur fugacity, oxygen fugacity, and ion activity are the critical physicochemical factors affecting Ge enrichment. High sulfur fugacity and low oxygen fugacity are favorable for Ge enrichment, while ion activity is the main factor contributing to the differential Ge enrichment in sphalerite from the two stages. These findings enrich the metallogenic theory of Ge-rich lead-zinc deposits and provide a scientific basis for the exploration and comprehensive utilization of Ge resources.

Zircon U-Pb Ages and Petrogenesis of Late Mesozoic Granitic Porphyries in the Northern Chaohu Area

WANG Ding, CHEN Yuming, TAN Mingzhen, HU Zhixin, LI Zhensheng, LI Quanzhong

2025, 39(04): 947-963. DOI: 10.19657/j.geoscience.1000-8527.2025.023

Asbtract ( 45 )

HTML ( 0)

PDF (13002KB) ( 26 )

Figures and Tables | References | Related Articles | Metrics

Compared with the intense Late Mesozoic magmatism in the adjacent Middle-Lower Yangtze River Metallogenic Belt and Tanlu Fault Zone, intrusive rocks in the northern Chaohu (Chaobei) area are limited in distribution and development. In this study, zircon LA-ICP-MS dating and whole-rock elemental geochemical analyses are used to determine the formation age and petrogenesis of granitic porphyries in the Chaobei area, thereby providing new constraints on the regional tectonic evolution during the Late Mesozoic. The Chaobei granitic porphyries belong to strongly peraluminous, high-K calc-alkaline granites, consisting of 15%-30% phenocrysts (fine-grained feldspar, minor quartz, and biotite) and 70%-85% matrix (micrograined feldspar and quartz or biotite). Three crystallization ages of the Chaobei granitic porphyries were obtained in this study: (106.0±3.7) Ma, (103.9±4.4) Ma, and (97.1±4.6) Ma, corresponding to the Albian (Early Cretaceous) to Cenomanian (Late Cretaceous). These porphyries are coeval with or slightly younger than the highly fractionated A-type granites (108-103 Ma) in the Tanlu Fault Zone and adakitic rocks (109-100 Ma) in the Ningzhen area. The Chaobei granitic porphyries are relatively lowly fractionated S-type granites, formed by partial melting of the thickened Lower Yangtze Block lower crust under relatively high-temperature conditions, in a far-field back-arc weak extensional setting associated with the ortho-subduction of the Paleo-Pacific Plate. The decreased Sr/Y ratio of the Chaobei granitic porphyries, combined with the adakitic rocks in the Ningzhen area, provides robust evidence for lithospheric thinning of the Lower Yangtze Block during the Albian. Moreover, the A-type granites and bimodal volcanic rocks in the Tanlu Fault Zone clearly indicate that it is an intense lithospheric thinning zone.

Late Cretaceous Volcanic Rocks and Stratigraphic Delimitation in the Nanyandang Mountain Area, Southeastern Zhejiang

PAN Shaojun, CHEN Xiaoyou, ZHANG Jianfang, ZENG Fanfei, GU Mingguang, MA Junxiang

2025, 39(04): 964-980. DOI: 10.19657/j.geoscience.1000-8527.2024.036

Asbtract ( 54 )

HTML ( 5)

PDF (11249KB) ( 27 )

Figures and Tables | References | Related Articles | Metrics

This study focuses on the Baiyunshan volcanic edifice in the Nanyandang Mountain area, southeastern Zhejiang. Zircon U-Pb dating was conducted on volcanic rocks and syenite porphyry from the central intrusion of the edifice, yielding 8 sets of high-precision data. Four volcanic rock samples and one syenite porphyry sample yielded ages ranging from 90.32 to 98.37 Ma, confirming intense volcanic activity in the region during the Late Cretaceous.Geochemical analysis of 6 Late Cretaceous volcanic clastic rock samples reveals the following characteristics: major elements are characterized by high silica, high alkali, low aluminum, depletion in Ca, Fe, Mg, P, and Ti, and high differentiation. Trace and rare earth elements show enrichment in large ion lithophile elements (Rb, K, Th, U), depletion in Ba, Nb, Sr, P, and Ti, and low contents of siderophile elements (Co, Ni, Cr). These features indicate that the volcanic rocks belong to quasi-aluminous to peraluminous high-K calc-alkaline series, with high degrees of fractional crystallization and crustal origin.The genesis of the Late Cretaceous volcanic rocks is attributed to the subduction of the Pacific Plate, which sustained upper crustal compression and extensional tectonics in southeastern Zhejiang from the Late Jurassic to the Late Cretaceous, triggering volcanic activity in the Nanyandang Mountain area.Recent discoveries of Late Cretaceous volcanic rocks in southeastern Zhejiang, with expanding outcrops, show lithological and geochemical differences from the Xiaoxiong Formation. To better “accommodate” these volcanic strata, it is proposed to establish a new “Yandang Mountain Group” and subdivide it into “Formation-Member” units based on lithological assemblages and geochemical characteristics.

Relationship between Gold Enrichment and Trace Element Migration in the Tectonic-Alteration Zone of the Xiadian Gold Deposit, Jiaodong Area

LI Jinhui, ZHANG Haidong, LEI Wanshan

2025, 39(04): 981-994. DOI: 10.19657/j.geoscience.1000-8527.2024.060

Asbtract ( 40 )

HTML ( 4)

PDF (10089KB) ( 13 )

Figures and Tables | References | Related Articles | Metrics

Jiaodong is the largest gold ore concentration area in China, characterized by massive and instantaneous mineralization, with intense fluid metasomatism. Alteration-type gold deposits are the most important type of gold deposits here, featuring large mineralization scale (accounting for approximately 2/3 of Jiaodong’s gold reserves), orebodies mainly occurring in the footwall of the Zhaoping fault zone, and gold mineralization closely related to beresitization and rock fragmentation degree. However, the relationship between gold enrichment and element migration during mineralization and alteration remains poorly understood. This study focuses on the super-large Xiadian gold deposit (approximately 140 t, average grade 4.23 g/t) in the Zhaoping fault zone, conducting petrographic observation of the tectonic-alteration zone and mass balance calculation of trace elements. The results show that the tectonic-alteration zone can be divided into six lithological zones: fault gouge, beresitic cataclasite zone, weakly fragmented mylonite zone, fragmented beresitic granite zone, fragmented granite zone (with pyrite-bearing quartz veins), and syenogranitic cataclasite zone. Gold enrichment is closely related to altered minerals such as secondary quartz and pyrite, followed by sericite. The pyrite-sericite-quartz cataclastic rock zone is a gold-enriched zone. The migration rates of strongly active elements (Au, Ag, W), active elements (Cs, Ba, Rb), and weakly active elements (Pb, Sr) increase in the altered zone, with migration being particularly evident in the pyrite-sericite-quartz cataclastic rock zone. Transitional elements (Cr, Ni) show migration out of the zone. The migration-out rate of pyrite-sericite-quartz cataclastic rocks near the tectonically altered zones on both sides decreases significantly, with local migration-in characteristics.The migration rate of LREE near the fault gouge end shows minor changes (-1.2%~-3.7%). High field strength elements (HREE) show almost no significant changes within the alteration zone. The protolith of the beresitic cataclasite zone is plagiogranite; thus, ore-forming fluids underwent intense metasomatism along the main fault zone (F1) in plagiogranite, accompanied by element migration (both into and out of the zone) and gold enrichment. This indicates that ore-forming fluids strongly altered the surrounding rocks, which may be the main reason for large-scale mineralization in the Jiaodong area.

Petrological Characteristics and Petrogenetic Significance of Mesozoic Xiaodaqingshan Granite in Jining Area, Inner Mongolia

WU Jiangwei, HU Hao, ZHANG Fuchen, NIU Yi, ZHOU Zhiguang, ZHANG Da

2025, 39(04): 995-1015. DOI: 10.19657/j.geoscience.1000-8527.2024.027

Asbtract ( 39 )

HTML ( 3)

PDF (18264KB) ( 20 )

Figures and Tables | References | Related Articles | Metrics

The Mesozoic magmatic rocks in the middle segment of the northern margin of the North China Craton have complex petrological characteristics, and there are divergent understandings on the formation of granites, which restricts the in-depth understanding of petrogenetic dynamics. In this paper, the Mesozoic Xiaodaqingshan granite pluton in Inner Mongolia, located in this tectonic belt, is selected as the research object. Studies on petrography, zircon U-Pb dating, whole-rock element composition, and Sr-Nd-Pb isotope composition are carried out to explain the genesis and source properties of the magmatic rocks, and to further discuss the Mesozoic tectonic dynamic environment in the study area. The results show that the weighted average ²⁰⁶Pb/²³⁸U age of zircons from monzogranite is (135.4±1.2) Ma, indicating that the host granites formed in the Early Cretaceous. The rocks are characterized by high silica (73.37%-77.21%), high alkali (5.93%-8.78%), and high aluminum saturation index (1.02-1.32), belonging to the peraluminous high-K calc-alkaline series. They are enriched in large ion lithophile elements (Rb, K) and high field strength elements (Th, U), depleted in Nb, Ba, Sr, Ti, and P; enriched in light rare earth elements and depleted in Eu; with low (⁸⁷Sr/⁸⁶Sr)_i values (0.7094-0.7391), highly negative ε_Nd(t) values (-15.37 to -16.19), ²⁰⁶Pb/²⁰⁴Pb ratios of 17.158-17.365, ²⁰⁷Pb/²⁰⁴Pb ratios of 15.437-15.442, and ²⁰⁸Pb/²⁰⁴Pb ratios of 37.881-38.082. Comprehensive geochemical characteristics indicate that the Xiaodaqingshan granite is a highly differentiated I-type granite, mainly derived from partial melting of lower crustal materials. Combined with regional geological evidence, it is considered that the Xiaodaqingshan granite in Jining area, Inner Mongolia, formed in the post-orogenic stage, and its formation may be controlled by the combined effects of the closure of the Mongolia-Okhotsk Ocean basin and the subduction of the Paleo-Pacific Plate.

Petrogenesis of the Concealed Monzogranite in the Bainiuchang Ag-polymetallic Deposit, Southeastern Yunnan, and Its Implications for Ag-polymetallic Mineralization: Constraints from U-Pb Geochronology, Geochemistry, and Hf Isotopes

MI Xue, LIU Xuelong, ZHANG Shitao, CHEN Shufu, MENG Guangzhi, ZHANG Hong, CHENG Jialong, ZHOU Jiehu, LU Bode, DAO Junshan, SHI Nan, FAN Maohuang

2025, 39(04): 1016-1038. DOI: 10.19657/j.geoscience.1000-8527.2024.119

Asbtract ( 48 )

HTML ( 7)

PDF (13873KB) ( 25 )

Figures and Tables | References | Related Articles | Metrics

The Bainiuchang silver polymetallic deposit, one of the super-large deposits in southeastern Yunnan, is located in the northwestern part of Bozhu Mountain, southeastern Yunnan. Based on systematic fieldwork, this study conducted LA-ICP-MS zircon U-Pb dating, whole-rock geochemical analysis, and zircon Lu-Hf isotope analysis on the concealed monzogranite in Bainiuchang to determine the formation age, genesis, magma source, and alteration effects of the deep concealed granite. Combined with the tectonic setting, the relationship between the concealed granite and mineralization was analyzed. The results show that the zircon U-Pb ages of four monzogranite samples from Bainiuchang are (87.7±0.5) Ma, (87.34±0.4) Ma, (88.5±0.5) Ma, and (87.1±0.5) Ma, respectively, all belonging to the late Yanshanian period. The Bainiuchang monzogranite is characterized by high silicon (SiO₂=66.27%-73.77%) and high alkali (Na₂O+K₂O=6.17%-8.48%) contents, with high total rare earth elements (ΣREE=172.49×10^-6-333.22×10^-6, average 271.30×10^-6), obvious fractionation of light and heavy rare earth elements (LREE/HREE=12.74-20.47, average 16.76), and weak negative Eu anomalies (0.44-0.78). It is relatively enriched in large ion lithophile elements (Rb, K) and high field strength elements (Th, U, Ce, Zr, Hf, Ta), belonging to peraluminous high-K calc-alkaline S-type granite. The zircon ε_Hf(t) values of the Bainiuchang monzogranite range from -21.5 to -4.3, with corresponding two-stage Hf model ages of 1259-1614 Ma, indicating that the magma was derived from the melting of Mesoproterozoic-Neoproterozoic ancient crustal materials. Comprehensive analysis suggests that the formation of the Bainiuchang F3 fault provided migration channels and space for deep magmatic activity in the study area. The upwelling of granitic magma transported ore-forming elements such as Sn, Cu, and Zn, and consolidated to form the deep concealed granite. The formation of the deep concealed monzogranite in Bainiuchang is closely related to the tectonic transition from syn-collision to post-collision orogeny in the late Yanshanian period.

Petrogenesis and Uranium Mineralization Potential of Granites Hosting the Xiaoshan Deposit in the Lujing Uranium Ore Field, Jiangxi Province

LI Furong, PAN Jiayong, ZHONG Fujun, ZENG Renyu, YAN Jie, Huang Di, DANG Feipeng

2025, 39(04): 1039-1058. DOI: 10.19657/j.geoscience.1000-8527.2025.020

Asbtract ( 51 )

HTML ( 0)

PDF (13416KB) ( 16 )

Figures and Tables | References | Related Articles | Metrics

The South China Block is a significant region for granite-type uranium deposits in China. The Lujing uranium ore field, located on the southwest side of the Taoshan-Zhuguang uranium metallogenic belt, is one of the most important granite-type uranium ore fields in South China. In recent years, the Xiaoshan deposit, a medium-sized uranium deposit, has been newly discovered in the central part of the Lujing uranium ore field. Uranium mineralization in the Xiaoshan deposit is closely related to alkaline metasomatism, with ore bodies hosted in granite. The study of ore-hosting granites in the Xiaoshan deposit, Jiangxi Province, provides key geological evidence for understanding the genesis of Indosinian granites and their uranium metallogenic specialization in South China. For this purpose, this study focuses on the ore-hosting granites of the Xiaoshan uranium deposit. By conducting detailed petrographic observations and geochemical analyses, it explores the genesis, tectonic setting of the granites, and their constraints on uranium mineralization. The research reveals that the ore-hosting granites in the Xiaoshan deposit mainly consist of medium-coarse-grained porphyritic biotite granite and fine-grained two-mica granite, with zircon U-Pb ages of 237.3±1.5 Ma and 236.8±1.6 Ma, respectively, indicating that they are the products of early Indosinian magmatism. Petrographic, geochemical, and zircon Hf isotopic characteristics show that the ore-hosting granites have features of S-type granites, formed in a tectonic setting transitioning from compression to extension. Their source area is mainly Paleoproterozoic metamudstone, resulting from partial melting of crustal materials. Both types of granites in the Xiaoshan deposit are uranium-rich and serve as important uranium source rocks for uranium mineralization in the region.

Climatic Evolution Characteristics in the Upper Hanjiang River Since the Late Pleistocene: Evidence from Soil Geochemistry of the Zhujia Village Section

ZHAO Chao, WEI Xiang, SUN Jianwei, GONG Wenqiang, ZHAO Hao, LI Xiaoming, ZHENG Jianfeng, ZHAO Lilei

2025, 39(04): 1059-1067. DOI: 10.19657/j.geoscience.1000-8527.2024.056

Asbtract ( 44 )

HTML ( 3)

PDF (3277KB) ( 16 )

Figures and Tables | References | Related Articles | Metrics

The Quaternary is a period of rapid climatic fluctuations, and loess records abundant paleoclimatic information. To explore the process of climate change in the Upper Hanjiang River since the Late Pleistocene, this study investigated the sedimentary characteristics, distribution of major elements, geochemical parameters, and formation age of the Zhujia Village section, which is located on the first river terrace of the Hanjiang River in Yang County, upper reaches of the Hanjiang River. The results indicate that the first river terrace in the upper reaches of the Hanjiang River formed around 50 ka BP; the section has a typical stratigraphic sequence from bottom to top: loess (L₁)→paleosol (S₀)→Holocene loess (L₀)→topsoil (TS); the main chemical components of the section are SiO₂, Al₂O₃, and Fe₂O₃; during chemical weathering, Ca and Na elements are more strongly leached and migrated, while K and Mg elements are relatively weakly leached and migrated; the degree of chemical weathering in the section gradually increases from typical loess (L₁) to paleosol (S₀), and slightly decreases in the Holocene loess (L₀) layer, recording the regional climatic evolution process: dry and cold during 50~11 ka BP, gradually warming and wetting since 11.00 ka BP, reaching the warmest and wettest at 2.50 ka BP, and continuously cooling and drying during 2.50~0 ka BP. The research results can provide data reference for the reconstruction of paleoclimate in the northern subtropical zone of China.

Geochemical Baseline and Background Values of Soil in Major Agricultural Regions of Heilongjiang Province

LIU Lifen, LUAN Xinting, LI Ying, YANG Xing, JIANG Qinglong, GAO Bo, LIU Xiaolan

2025, 39(04): 1068-1082. DOI: 10.19657/j.geoscience.1000-8527.2024.143

Asbtract ( 40 )

HTML ( 0)

PDF (1093KB) ( 21 )

Figures and Tables | References | Related Articles | Metrics

Heilongjiang Province is a key commodity grain production base in China. Research on soil geochemical baseline and background values is crucial for scientifically assessing soil environmental quality and strengthening the protection and utilization of black soil resources. Based on data from multi-target regional geochemical surveys and land quality geochemical surveys conducted in Heilongjiang Province between 2005 and 2021, this study analyzed 54 elemental indicators in deep and surface soils of the province’s major agricultural regions using descriptive statistical methods. It clarified the content ranges and variation characteristics of each indicator, conducted normal and log-normal distribution tests on the data, calculated the baseline and background values for each element, and performed regional statistics for 12 cities including Harbin and Daqing.The results show that:(1) Most elemental indicators in surface and deep soils have similar characteristic parameters, reflecting a close relationship between soil elemental composition and parent material in the study area;(2) Differences in soil baseline and background values across cities in Heilongjiang are influenced by factors such as topography, parent material, and local soil salinization;(3) Soil geochemical background values broadly reflect the current status of soil nutrients and environmental quality. The study area has abundant nutrient indicators such as N, P, and Corg, with baseline and background values higher than the national average. Additionally, heavy metal pollutants like Pb and Cd have low background levels, indicating excellent soil environmental quality and favorable conditions for green agriculture development in Heilongjiang Province.Covering major agricultural regions of Heilongjiang, this study provides a reference for regional land resource management, ecological protection, and related fields.

The Sedimentary Environment and Provenance Analysis of the Lower Cretaceous Gaofengsi Formation in South-Central Chuxiong Basin, Central Yunnan Province, Southwest China

CHEN Baichen, PAN Dong, ZHANG Jiahui, LI Suoming, WANG Wanneng, XUE Chuandong

2025, 39(04): 1083-1097. DOI: 10.19657/j.geoscience.1000-8527.2025.019

Asbtract ( 50 )

HTML ( 3)

PDF (20000KB) ( 22 )

Figures and Tables | References | Related Articles | Metrics

The Late Mesozoic Chuxiong Basin, located at the southwest margin of the Yangtze Plate, is widely developed with Cretaceous red clastic rock series, hosting copper orebodies in multiple horizons and thus forming the most representative sandstone-type copper ore-concentrated area in China. The lithological assemblage of the Lower Cretaceous Gaofengsi Formation in the Chuxiong Basin shows significant spatial variations, and relevant research remains inadequate, which has restricted studies on the tectono-sedimentary paleogeographic evolution of the Chuxiong Basin during the Early Cretaceous, as well as the evaluation of regional resource potential and the deployment of mineral exploration and reserve increase. Focusing on the Lower Cretaceous Gaofengsi Formation in the central and southern parts of the basin, this study employs methods such as geological profile measurement, observation of rock (assemblage) and sedimentary fabrics, analysis of sandstone component characteristics, measurement of paleocurrent directions, and heavy mineral analysis, combined with regional geological survey data, to clarify the sedimentary sequence, rock (assemblage) characteristics, types of sedimentary facies, and sources of sedimentary materials.The results indicate that:(1) The Gaofengsi Formation in the study area is generally composed of meandering river facies and delta facies. The northeastern part is dominated by meandering river facies with bank subfacies as the main type, while the southwestern part is dominated by delta facies. The sedimentary environment underwent a transition from arid to humid climate from bottom to top;(2) The sediment source area is located in the paleo-highlands in the eastern and northeastern parts of the basin, where sedimentary rocks are mainly exposed, accompanied by a small amount of acidic, basic igneous rocks and metamorphic rocks;(3) The Chuxiong Basin was generally in a tectonically stable period during the Early Cretaceous. Among them, the sandstones of the Gaofengsi Formation with high detrital content and low sorting coefficient are favorable hosting horizons for sandstone-type copper deposits, showing good prospecting potential.Covering the main areas of the central and southern Chuxiong Basin, this study provides new data for regional reconstruction of sedimentary paleogeography and mineral exploration.

Geochemical Characteristics and Influencing Factors of Selenium in Soil-Crop System of Qing’an Area, Heilongjiang Province

LIU Ting, ZHANG Li, LÜ Shijia, ZHANG Siyu, WANG Gang, SUN Zhenwei

2025, 39(04): 1098-1107. DOI: 10.19657/j.geoscience.1000-8527.2024.058

Asbtract ( 46 )

HTML ( 0)

PDF (5311KB) ( 20 )

Figures and Tables | References | Related Articles | Metrics

Selenium (Se) deficiency is widespread in China’s soils. In recent years, large areas of selenium-rich soil zones have been discovered in the Songnen Plain; however, there is a lack of systematic scie.pngic evaluation, and research on the formation mechanism of selenium and its influencing factors is insufficient, which seriously restricts the development and sustainable utilization of selenium-rich land. Taking soil and crops in Qing’an Area, Heilongjiang Province as the research object, 8689 surface soil samples, 40 vertical soil profile samples, and 180 sets of crop and root soil samples were collected. Physical and chemical indicators such as total selenium and heavy metal elements in various samples were analyzed and tested.The results show that:(1) The selenium content in surface soil ranges from 0.03 to 0.93 mg/kg, with an average of 0.28 mg/kg, mainly dominated by selenium-sufficient soil (accounting for 93.93%). The vertical distribution of Se shows a surface-aggregated pattern with obvious secondary enrichment;(2) Soils developed from lacustrine sediments have relatively high Se content. Soil types have little impact on Se content, with black soil and meadow soil having relatively higher Se content. Under different land use patterns, cultivated land has higher Se content. The Se enrichment capacity of different crop grains in descending order is: rice>soybean>corn;(3) Correlation analysis and statistical results among elements indicate that parent material, soil organic matter, and pH are the main factors affecting soil Se content in the study area. Soil selenium and soil organic matter are key factors influencing Se content in crop grains. It is recommended that adjusting the planting structure by gradually replacing corn with rice and soybean in this region can reduce the risk of selenium deficiency in crops, meeting residents’ selenium-related health needs.

Evaluation and Development Potential of Selenium-rich Land Resources in Lixiahe Plain, Jiangsu Province

ZHOU Xin, LIU Qiang, DING Xiaoqin, YANG Guifang, WANG Danling

2025, 39(04): 1108-1118. DOI: 10.19657/j.geoscience.1000-8527.2024.023

Asbtract ( 38 )

HTML ( 3)

PDF (4279KB) ( 18 )

Figures and Tables | References | Related Articles | Metrics

The development of natural selenium-rich land resources has attracted growing attention; however, there are still deficiencies in the evaluation criteria for selenium-rich soils in plain areas far from parent rocks, such as insufficient assessment of selenium availability and incomplete consideration of organic matter. Based on the 1∶50,000 land quality survey, this study conducted zoning of selenium-rich land resources and evaluation of their development potential in the Lixiahe Plain of Hai’an City, Jiangsu, aiming to provide a basis for the layout planning and development of local selenium-rich agriculture. The results showed that the soil selenium content in the lagoon facies sedimentary area of the study area was significantly higher than that in the surrounding soils, with the highest selenium content reaching 0.63 mg·kg^-1 and the enrichment area covering approximately 66 km². Soil selenium exhibited extremely significant correlations with parent material, soil texture, topographic conditions, and soil organic matter (SOM), with correlation coefficients of 0.60, 0.36, -0.60, and 0.86, respectively (P<0.01). The selenium-rich soils were formed by supergene enrichment of parent materials from ancient lagoon facies. SOM played a crucial role in adsorbing and fixing selenium during soil formation, serving as a key factor for selenium enrichment in surface soils. Using an improved evaluation method for selenium-rich soils, this study delineated the distribution of high-quality selenium-rich areas, general selenium-rich areas, and potential selenium-rich areas, with areas of 9.87 km², 23.42 km², and 32.96 km², respectively. The selenium enrichment rates of wheat in these areas were 86.7%, 63.3%, and 33.3%, while those of rice were 50%, 25%, and 5%, respectively. The highest selenium content in wheat grains was 0.20 mg·kg^-1, indicating that wheat is more likely to absorb selenium than rice. The study area is rich in organic matter, with high comprehensive land quality, and the selenium-rich areas are distributed in contiguous patches, showing potential for developing natural selenium-rich wheat and rice.

Analysis of Groundwater Level Dynamics and Influencing Factors in the Chaobai River Basin from 2019 to 2022

ZHANG Tianyu, XU Congchao, ZHANG Qin, ZHANG Shuqi, SHI Bowen, LIU Di, YANG Yihong, CHEN Nan, LI Rui

2025, 39(04): 1119-1128. DOI: 10.19657/j.geoscience.1000-8527.2024.141

Asbtract ( 40 )

HTML ( 2)

PDF (6210KB) ( 10 )

Figures and Tables | References | Related Articles | Metrics

The Chaobai River Basin is an indispensable water supply area for Beijing. Studying groundwater level dynamics helps identify changes in groundwater levels, which is of great significance for the protection and management of groundwater resources. Based on groundwater level monitoring data of the Chaobai River Basin from 2019 to 2022, this paper analyzes the intra-annual and interannual trends of groundwater levels, as well as the main factors influencing groundwater level dynamics, using GIS technology, SOM clustering analysis, linear trend analysis, principal component analysis (PCA), and multiple linear regression analysis, combined with data on rainfall, extraction, and water consumption.The results show that the groundwater level dynamics of the 27 monitoring wells fall into three categories: strong fluctuation, medium fluctuation, and weak fluctuation, with intra-annual water level changes of 4.2 m, 3.2 m, and 1.5 m, respectively. From 2019 to 2022, the average annual change in groundwater levels ranged from 0.0258 to 0.597 m/a. Principal component analysis extracted two principal components (representing human activity factors and natural factors, respectively) with eigenvalues of 6.21 and 1.59, and a cumulative contribution rate of 89.224%. Multiple linear regression analysis showed that human activities were the main factors affecting groundwater levels, with domestic water use, environmental water use, South-to-North Water Diversion Project replenishment, and ecological water replenishment identified as the primary influencing factors. This study provides a theoretical basis for groundwater management and protection in the Chaobai River Basin.

Restoration of Paleosedimentary Environment of the Top of Zhiluo Formation in the Southern Margin of Ordos Basin: Evidence from Geochemical Characteristics of Mudstone

CHENG Xianyu, ZHANG Tianfu, ZHANG Yun, HE Peng, SUN Lixin, MA Hailin, LU Chao

2025, 39(04): 1129-1142. DOI: 10.19657/j.geoscience.1000-8527.2024.144

Asbtract ( 39 )

HTML ( 4)

PDF (5660KB) ( 16 )

Figures and Tables | References | Related Articles | Metrics

Geochemical evidence from Jurassic mudstones in the southern part of the Ordos Basin records the evolution of paleosedimentary environments, and the evolution of the Middle Jurassic paleoenvironment forms the basis for the sedimentary enrichment of uranium. However, understanding of the sedimentary environment of the Zhiluo Formation in the southeastern Ordos Basin remains insufficient, restricting in-depth understanding of the formation conditions of sandstone-type uranium deposits. This study conducts major and trace element analyses on mudstones from the Middle Jurassic Zhiluo Formation and the top of the Yan’an Formation in the Diantou area of Huangling County. Based on vertical variations in typical geochemical parameters of the mudstones, the paleosedimentary environment is reconstructed. Results show that: combinations of B, equivalent B content, and Sr/Ba indicate that the sedimentary water of the Zhiluo Formation was in a brackish to slightly saline environment; combinations of U/Th, V/(V+Ni), V/Cr, and Ni/Co indicate that the paleowater medium at the top of the Yan’an Formation and Zhiluo Formation was oxygen-rich; Fe²⁺/Fe³⁺ ratios indicate that the Yan’an Formation formed a stable reducing layer, with the bottom of the upper submember of the lower member of the Zhiluo Formation gradually transitioning to a weakly reducing environment, and the upper member of the Zhiluo Formation being a strongly oxidizing environment; paleoclimate indicators (Sr, Sr/Cu, Al₂O₃/MgO, FeO/MnO) reveal that the Zhiluo Formation sedimentary period experienced a transition from semi-arid to arid conditions; Chemical Index of Alteration (CIA) and Index of Compositional Variability (ICV) reflect weaker chemical weathering in the upper member of the Zhiluo Formation compared to the lower member, indicating intensified tectonic activity around the Ordos Basin. The gradual increase in provenance input, paleoclimate changes during the Zhiluo period, and the transition of the paleowater environment from reducing to oxidizing conditions played a key role in constraining uranium enrichment and mineralization in this area.

Numerical Simulation of the Influence of Aquifer Leakage Recharge on CBM Productivity:A Case Study from Shizhuan South Block

YAN Xinlu, TANG Shuheng, FU Xiaokang, DONG Xianshu, LI Zhongcheng, DENG Zhiyu, MENG Yanjun

2025, 39(04): 1143-1155. DOI: 10.19657/j.geoscience.1000-8527.2024.130

Asbtract ( 43 )

HTML ( 2)

PDF (11825KB) ( 12 )

Figures and Tables | References | Related Articles | Metrics

Aquifer leakage recharge is a common issue in coalbed methane (CBM) development in China, significantly hindering efficient production. Taking a vertical CBM well in the Shizhuang South Block of the Qinshui Basin as a case study, this research comprehensively evaluates the impact of aquifer leakage recharge parameters on CBM well productivity through numerical simulation and sensitivity analysis.The results indicate that classifying aquifers into finite and infinite recharge types based on their water supply capacity is the fundamental reason for the varying effects of leakage recharge. The location, morphology, and spatial distribution of water-conducting fractures relative to hydraulic fractures exhibit high sensitivity to productivity characteristics: in infinite recharge aquifers, they primarily affect gas production volume, while in finite recharge aquifers, they influence the shape of gas production curves.The sensitivity of aquifer leakage recharge parameters to coalbed methane productivity, from strongest to weakest, is aquifer type, properties of leakage channels, aquifer physical properties, and formation water properties.Based on these findings, a production discrimination flowchart is developed, categorizing CBM well productivity characteristics under the influence of aquifer leakage recharge into six types, and further delineating the distribution of wells with different productivity characteristics in the study area. This flowchart provides scientific guidance for analyzing CBM productivity characteristics and evaluating productivity potential under the influence of aquifer leakage recharge.

Coupling Relationship Between the Reservoir Densification Process and Hydrocarbon Charging Process in the Ahe Formation in the Dibei Area of the Kuqa Depression

JING Taotao, LI Wenhao, DONG Wei, CHEN Yifan, WANG Longwei, YANG Yifang

2025, 39(04): 1156-1168. DOI: 10.19657/j.geoscience.1000-8527.2024.072

Asbtract ( 40 )

HTML ( 0)

PDF (14607KB) ( 8 )

Figures and Tables | References | Related Articles | Metrics

The Lower Jurassic Ahe Formation is a key target for tight oil and gas exploration in the Dibei area. In recent years, industrial oil and gas flows have been obtained from Wells Dibei 2 and Dibei 5, demonstrating favorable exploration prospects in the area, which also serves as a critical replacement zone for oil and gas exploration in the Kuqa Depression. Previous studies have systematically investigated hydrocarbon sources and accumulation conditions in the Dibei area, but research on the quantitative characterization of porosity evolution remains limited, and controversies persist regarding whether hydrocarbon charging occurred in two or three stages.In this study, sandstone samples from Wells Dibei 5 and Ditan 2 were analyzed using casting thin sections, scanning electron microscopy (SEM), cathodoluminescence, and fluid inclusion thermometry. These methods helped identify diagenetic types, clarify the diagenetic evolution sequence, quantitatively characterize the reservoir porosity evolution history using the inversion backstripping principle, and elaborate on the coupling relationship between reservoir densification and hydrocarbon charging.The results indicate that the Ahe Formation in the Dibei area underwent diagenetic processes including compaction, dissolution, and cementation, with intense compaction being the primary cause of underdeveloped primary pores. The diagenetic sequence is as follows: mechanical compaction→early calcite cementation→quartz overgrowth→feldspar dissolution→crude oil charging→late calcite and ferrocalcite cementation→calcite dissolution and natural gas charging→tectonic compression, featuring multi-stage dissolution and cementation.The Ahe Formation reservoir has undergone two stages of hydrocarbon charging. The early-stage crude oil charging occurred in the early-middle Kangcun Formation (14.1-12.3 Ma), when the reservoir was not yet densified, though the crude oil charging was on a small scale. The late-stage natural gas charging took place in the middle-late Kangcun Formation (10.2-8.1 Ma), by which time the reservoir had already been densified (with the densification time at approximately 11 Ma). At this stage, the Triassic source rocks were in the mature to high-maturity stage, and inclusions were well-developed, indicating a high intensity of natural gas charging.Thus, the coupling relationship between reservoir densification and hydrocarbon accumulation in the Ahe Formation is characterized by “densification prior to accumulation”. These findings help clarify hydrocarbon enrichment patterns in the Ahe Formation and provide a basis for well placement.

Diagenetic Evolution and Distribution of Brine Reservoirs in the 4th to 5^th Members of the Jialingjiang Formation, Puguang Area, Northeastern Sichuan

MA Qiankun, CUI Xinyu, SU Kui, WU Kunming, ZHANG Yongsheng, SHANG Wenjun

2025, 39(04): 1169-1179. DOI: 10.19657/j.geoscience.1000-8527.2025.016

Asbtract ( 40 )

HTML ( 0)

PDF (9863KB) ( 11 )

Figures and Tables | References | Related Articles | Metrics

The 4th to 5th Members of the Early Triassic Jialingjiang Formation in the Puguang area, northeastern Sichuan, were deposited in a shallow epicontinental sea under a regressive environment, characterized by thick, unevenly interbedded carbonate rocks and evaporites. Previous studies have shown that the enrichment of lithium-rich potassium brine is closely related to the distribution of brine reservoirs, but this relationship has not been verified through diagenetic processes and evolutionary sequences, resulting in a critical gap in understanding the genetic mechanism of brines in the Jialingjiang Formation. Establishing the coupling relationship between diagenetic evolution of the Jialingjiang Formation and brine reservoir distribution is crucial for analyzing and exploring high-quality lithium-rich potassium brine.Based on analyses of typical diagenesis and diagenetic stage division of the 4th to 5th Members of the Jialingjiang Formation in the Puguang area using newly drilled Well CXD1, constructive diagenetic processes favorable for reservoir development in the study area include dissolution, metasomatism, and stress fracturing. These processes form reservoir spaces mainly consisting of structural fractures, intergranular dissolved pores, and intercrystalline dissolved pores.Comprehensive analyses of reservoir physical properties, single-well reservoir evaluation, and inter-well correlation indicate that there is a concentrated area of high-quality TypeⅡreservoirs in the Puguang area. The reservoir rock is a set of dissolved-pore dolomite, vertically developed in the gray-dolomite flat sedimentary microfacies of the T₁ $j 5 4 - 5$ substage, with stable northeastward extension. Planar distribution of these reservoirs is “inverted flask-shaped”, concentrated in the central-western and southern parts of Puguang.

Characteristics and Formation Mechanism of Limestone Reservoir of Shoals in the Middle Permian Maokou Formation: A Case Study of Shuanghechang Outcrop in Southeastern Sichuan

PAN Lei, QUAN Li, YANG Hao, XU Rui, WANG Guangwei

2025, 39(04): 1180-1192. DOI: 10.19657/j.geoscience.1000-8527.2025.029

Asbtract ( 39 )

HTML ( 2)

PDF (18767KB) ( 24 )

Figures and Tables | References | Related Articles | Metrics

The Permian Maokou Formation in the Sichuan Basin hosts diverse carbonate reservoirs with significant exploration potential. Previous studies have focused on dolomite and karst limestone reservoirs, leaving gaps in understanding the genesis of shoal-type porous limestone reservoirs, particularly their pore formation mechanisms and accumulation processes. Based on field outcrop observations, thin-section analysis, physical property testing, and geochemical data from eastern Sichuan, this study identifies pore types and diagenetic processes in Maokou Formation shoal limestones, reconstructs pore evolution histories, and establishes porosity-depth curves for reservoir characterization.Results show that shoal limestones are primarily sparitic bioclastic limestones, with locally dolomitized dolomite-bearing bioclastic limestones and cloud-patchy bioclastic limestones. Dolomite in dolomite-bearing limestones occurs as euhedral, scattered crystals, preferentially replacing bioclasts or aligning along microstylolites. Pore types are dominated by moldic pores, crystal moldic pores, and intragranular dissolved pores, with widespread asphalt linings on pore walls. Patchy dolomites in bioclastic limestones contain minor intercrystalline pores. Key diagenetic processes include compaction, dolomitization, pressure solution, burial dissolution, and burial cementation. Pore development is closely linked to penecontemporaneous meteoric water dissolution and selective burial dissolution of dolomite. Meteoric dissolution during early exposure formed isolated bioclast moldic pores, while burial dissolution along stylolites/fractures reflects organic acid leachingduring oil migration, preferentially dissolving dolomite along fluid pathways. These findings provide a theoretical framework for exploring Maokou Formation limestone reservoirs in the Sichuan Basin.

Table of Content