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Overview of the Application and Prospect of Common Chemical Weathering Indices LI Xulong, ZHANG Xia, LIN Chunming, HUANG Shuya, LI Xin Geological Journal of China Universities    2022, 28 (1): 51-63.   DOI: 10.16108/j.issn1006-7493.2020118 Abstract （3258）      PDF （1109KB）（4163）       Knowledge map    Save Common chemical weathering indices such as the Weathering Index of Parker (WIP), the Chemical Index of Alteration (CIA), the Index of Compositional Variability (ICV), CIX index and αAlE are often used to evaluate the chemical weathering intensity of source areas. But the factors which controlling the above chemical weathering indices should be considered, otherwise the results of the weathering evaluation will be distorted. This paper argues that the geological survey of source area should be known when chemical weathering indices are used to study the chemical weathering process. The selection of fine sediments or suspended matter can weaken the influence of grain size on chemical weathering indices. The impurities in the sediments are removed by acid treatment. Then, the Sc/Th-CIA diagram was used to reflect the material source information, Th/SC-Zr/Sc diagram was used to further distinguish the control effect of sedimentary differentiation and sedimentary recirculation, and then the samples with ICV value less than 1 were selected to eliminate the interference of recirculation. The A-CN-K diagram or the formula proposed by Panahi (2000) were used to correct the potassium metasomatism, and the strength of chemical weathering of source rocks was evaluated by CIA eventually. To ensure that the calculation of chemical weathering indices can accurately reflect the weathering situation of the source area, SPSS software can be used to analyze the proportion of some factors which affecting the CIA to construct characteristic weathering index of the study area. Related Articles | Metrics

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Advances in the Study of Biogeochemical Cycles of Phosphorus ZHOU Qiang, JIANG Yunbin, HAO Jihua, JI Junfeng, LI Wei Geological Journal of China Universities    2021, 27 (2): 183-199.   DOI: 10.16108/j.issn1006-7493.2020002 Abstract （1783）      PDF （2398KB）（1796）       Knowledge map    Save Phosphorus is an essential element for life and an important limiting factor for food production. The biogeochemical cycles of phosphorus not only regulate marine primary production, but also has an impact on the global climate system; it also determines the formation and distribution of phosphate resources and affects the continuity of life on earth. The current theory of “earth system science” integrates the subsystems of atmosphere, hydrosphere, lithosphere (crust and upper mantle) and biosphere, providing a broader view for studying the global phosphorus cycles. Based on the existing research and combined with the theory of “earth system science”, the following important understandings of the biogeochemical cycles of phosphorus has been obtained: The evolution of phosphorus in geological history determines the current cycle pattern of phosphorus on a global scale (terrestrial ecosystems and marine ecosystems); Human industrial and agricultural activities, as an important geological agent, has changed the biogeochemical cycles of phosphorus, resulted in resource crisis of phosphate depletion and environmental problem of eutrophication of water bodies; The key to solve the resource crisis problem of phosphorus shortage and environmental pollution problem of phosphorus surplus lies in regulating the biogeochemical cycle process that cause these problems.  Related Articles | Metrics

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Isolationand Sr 2+ MineralizationMediatedbyCarbonate MineralizationBacteria XU Fengqin, DAI Qunwei*, HOU Lihua, ZHAO Yulian, WU Qinqin, QIN Yonglian, J4    2015, 21 (3): 376-.   Abstract （977）      PDF （1574KB）（1860）       Knowledge map    Save  Soil pollution has increasingly become a serious problem, especially by radionuclide pollution, and has attracted wide attention. Microbial remediation of radionuclide contaminated soil has been studied and proposed as a potential strategy. Because some microorganisms in soil can consolidate heavy metal to form mineralization, heavy metal inos can be removed from soil. A strain of carbonate mineralization bacterium was isolated from the soil and was used for the mineralization of Sr2+. The final removal rate of 1.0 g/ L and 0.5 g/L Sr2 + was as high as 98% and 99% , respectively. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) analyses revealed that the mineralized product was strontium carbonate. It is suggested that indigenous bacteria can survive soil radionuclide toxicity and strontium ions could be mineralized as stable carbonate minerals, which indicates important practicability for radionuclide or heavy metal bioremediation. Also, the finding will provide new insights into carbonate biomineralization. Related Articles | Metrics

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Genesis Process of the Cretaceous Daqushan Pluton in Zhejiang Province: Crystal-Melt Separation and Magmatic Recharge HE Chen, XIA Yan, XU Xisheng, QIU Jiansheng, XU Hang, ZHANG Zhi, ZHAO Sidi Geological Journal of China Universities    2023, 29 (5): 657-678.   DOI: 10.16108/j.issn1006-7493.2022018 Abstract （1149）      PDF （11167KB）（1042）       Knowledge map    Save The models of trans-crustal magmatic system and crystal mush provide new insights into the study of Cretaceous magmatism in northeast China. The Daqushan pluton is located in the northeast of coastal Zhejiang and Fujian. It is mainly composed of K-feldspar granite with abundant melanocratic microgranular enclaves (MME) and is locally traversed by several mafic-intermediate dikes. A small outcrop of monzonite is exposed near the Chaotoumen. MME have a fine-grained texture with acicular apatites. Zircon U-Pb dating results show that the rock samples in the Daqushan pluton (including the K-feldspar granite, MME, monzonite, and mafic-intermediate dikes) crystallized at ~100 Ma. The K-feldspar granite are highly silicic (SiO2=68.45%-73.82%). While the miarolitic granite (DQS-7) without MME has the higher silica (76.27%), and its whole-rock geochemical and Sr-Nd isotope compositions are similar to those of coeval high silica granites (SiO2>75%) exposed around the Daqushan pluton. Daqushan K-feldspar granite bearing aggregates of plagioclase and K-feldspar exhibit“complementary”trace element geochemical characteristics with Daqushan miarolite and surrounding high silica granites. Further researches show that the Daqushan K-feldspar granite and miarolite were formed by felsic magma which originated from the partial melting of the ancient crustal basement and was recharged by mantle-derived magma. Such felsic magma underwent fractional crystallization and the extraction of high silica melt. Then, the residual silicic cumulate of the crystal mush and high silica melt crystallized and formed the Daqushan K-feldspar granite, miarolite and the surrounding coeval high silica granites. The mafic dikes of Daqushan are enriched in LILEs and depleted in HFSEs and are derived from the partial melting of the enriched mantle metasomatized by subducted dehydration fluids. The results of EPMA analyses indicate that the plagioclase in the K-feldspar granite and MME has a core-mantle-rim texture with low- An in the core (27-36, 25-41) and rim (17-32, 18-26) and relatively high-An in the mantle (28-57, 27-65). Integration of the element geochemical characteristics and Sr-Nd-Hf isotopic results, monzonite and intermediate dikes should be the product of magma mixing of mantle-derived mafic magma and felsic magma, while MME are the product of magma mingling of the two endmembers. The results of the Al-in-hornblende geobarometer show that the crystallization depth of MME is 1.8- 3.0 km, hornblende in monzonite develops core-mantle-rim texture, the crystallization depth of hornblende core and mantle is 17.0-21.2 km, and the depth of hornblende rim is 1.9-4.5 km. Based on the study of the origin and genetic relationships of K-feldspar granite, MME, miarolite, monzonite and mafic-intermediate dikes, and compared with the surrounding coeval high silica granites, this study establishes a model of trans-crustal magmatic systems for Daqushan pluton. The rollback of the subducting paleo-Pacific plate, the back-arc extension in the coastal area and the upwelling of the asthenosphere led to the underplating of the mantle-derived mafic magma, and further induced the partial melting of basement rocks in the lower crust to produce felsic magma. The continuous recharge and heating of mantle-derived magma favor the existence of long-lived melt-bearing regions in magma chambers, promoting magma differentiation and crystal-melt separation and thus forming two magma chambers with depths of 17-21 km and 2-3 km, respectively. K-feldspar granite, high silica granites, monzonite, MME and intermediate-mafic dikes were formed by magma mingling/mixing and crystal-melt separation in two connected magma chambers at different depths. Related Articles | Metrics

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Genetic Types and Accumulation of Crude Oil in the Central Inversion Zone in the Liaoxi Depression, Bohai Sea TIAN Derui, NIU Chengmin, WANG Deying, GUO Tao, PAN Wenjing, GUO Longlong Geological Journal of China Universities    2021, 27 (4): 444-458.   DOI: 10.16108/j.issn1006-7493.2020093 Abstract （418）      PDF （1211KB）（1094）       Knowledge map    Save The central inversion zone of the Liaoxi Depression is the enrichment area of high quality light crude oil in the Liaodong Bay exploration area. However, the genetic types, source and accumulation of crude oil have not been systematically studied. Based on the analysis and comparison of the biomarkers, three sets of effective source rocks of the Shahejie Formation were distinguished. The first, third and fourth members of the Shahejie Formation, are obviously different in the source of organic matter and sedimentary environment. It is confirmed that plankton is the main component of organic matter in the three sets of source rocks. The first member of the Shahejie Formation (E2s1) has the highest plankton content and the least terrestrial organic matter input. The content of dinoflagellate in the fourth member of the Shahejie Formation (E2s4) was significantly higher than that in the first and third members of the Shahejie Formation (E2s1, E2s3). Both E2s3 and E2s4 source rocks were deposited in the freshwater and weakly alkaline reducing environment, and the E2s1 source rock was deposited in the brackish to saline alkaline strongly reducing environment. The crude oil found in the central inversion zone can be divided into three source-related types through hierarchical cluster analysis(HCA). The oil-source correlation results show that the type Ⅰ crude oil is the mixed oil originated from the E2s3 and E2s1 source rocks, which is mainly distributed in the middle block and the middle area of the east block on the central inversion zone. The type Ⅱ crude oil is originated from the E2s4 source rocks, which is distributed in the southern area of the east block on the central inversion zone. The type Ⅲ crude oil is the mixed oil originated from the E2s3 and E2s4 source rocks, which is mainly distributed in the west block and the northern area of the east block on the central inversion zone. On this basis, the main controlling factors of hydrocarbon accumulation in the central inversion zone of the Liaoxi sag were analyzed. Oil and gas reservoirs on the central inversion zone are controlled by multiple factors, including the distribution of effective source rocks and the math of fault and sand bodies. Related Articles | Metrics

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Predevonian Tectonic Evolution of South China: from Cathaysian Block to Caledonian Period Folded Orogenic Belt SHU Liang-shu J4    Abstract （2106）      PDF （501KB）（4235）       Knowledge map    Save The interpretation of Predevonian tectonics of South China is controversial long time both on its age and distribution. Based on the middle-high grade metamorphic rocks, ductile slipping rheologic structures exposed in the the Zhejiang- Fujian-Jiangxi-Guangdong domain and high quality dating data published recently, the author believes that an ancient continental block existed certainly in South China, which is composed of Proterozoic schist, gneiss and migmatite with an oldest age of 2 Ga, their protolites are clastic rocks, volcanic rocks and plutons. This old land is temporarily called as Cathaysian Continental Block which is limited in the domain between Shaoxing-Jiangshan-Pingxiang fault and Zhenghe-Dapu fault, and its scope is less than that defined by Grabau. During 800-900 Ma, following the closure of paleo-South China ocean, Cathaysian block collided with Yangzi block and then became a part of Rodinia supercontinent. Not long time after converging, by affection of breakup of Rodinia supercontinent, proto-Cathaysian continental block was split into three sub-blocks, namely the southeastern Zhejiang-northwestern Fujian, the central-southern Jiangxi and the Yunkaidashan, and several rifts or sea channels occurred among them. From Early Sinian to Late Ordovician, these sea channels were expanded and were filled by 10000-20000 m thick clastic rocks (containing limestone) and turbidites. However coeval ophiolite and volcanic rocks are absent, implying extended fault did not reach to upper mantle. New geochronological results indicate that the ophiolite and volcanic rocks in the study areas, which were described as Early Paleozoic by previous researchers, yielded pre-Sinian ages, concentrating mainly between 800 Ma and 900 Ma. Thus, the previous Early Paleozoic tectonic framework needs to be re-constructed. In Silurian, a strong tectono-thermal event took place in South China, causing closure of Sinian-Early Paleozoic sea channels and folding-uplifting of mega-thick sediments. The South China Caledonian fold and orogenic belt was formed on the Proterozoic metamorphic basement. In the study area, folding deformation and ductile slipping rheology are very common, including thrust and strike-slip deformation, the peak period of deformation is 420-400 Ma. At the same time, a violent granitic magmatism was started, forming numerous strongly peraluminous S-type granites with A/CNK (molar Al2O3/[CaO + Na2O + K2O]) > 1.1, and I-type granitoids is rare. Peak period of granitic magmatism took place in the 430-400 Ma. Then, the whole South China Caledonian folded geological bodies were overlain unconformably by Late Devonian conglomerate and coarse sandstone, indicating termination of folding and orogeny. From Late Devonian, a united paleo-geographic and sedimentary environment occurred really in the study domain and its neighboring areas. Related Articles | Metrics

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The Quantitative Analysis Methods for Iron Oxides in Sediment and Their Application in Cretaceous Oceanic Red Beds LI Xiang, CAI Yuanfeng J4    2014, 20 (3): 433-.   Abstract （834）      PDF （1087KB）（2395）       Knowledge map    Save Hematite and goethite are the most stable iron oxides in nature and widely present in different compartments of the global system. They are responsible for the color origin of many types of sediment. In addition, the formation and preservation of hematite and goethite have been used to track palaeoenvironmental information. There are several approaches to characterizing and distinguishing hematite and goethite, but the quantifying of the concentrations of hematite and goethite in natural samples has been restricted by low concentration, relative poor crystalline and fine-grained as well as the limits of specific analysis methods used. In this paper, the most common quantitative methods of hematite and goethite, including X-ray diffraction (XRD) and diffuse reflectance spectroscopy (DRS), have been introduced. Based on the qualitative analysis of the Cretaceous Oceanic Red Beds (CORBs) samples, we used the K-value method to quantify the hematite contents in the red shale samples from the Chuangde section in Tibet and obtained the hematite contents ranging from 3.81% to 8.11%. Analysis using DRS with multiple linear regression was performed to obtain the absolute contents of iron oxides within Aptian-Albian cyclic oceanic red beds in ODP Hole 1049C 12X Core, North Atlantic. The results reveal that the brown beds contain 0.13~0.82% hematite and 0.22~0.81% goethite. The orange beds contain 0.19~0.46% hematite and 0.29~ 0.67% goethite. The comparison of the calculated results with the test data shows that both methods were feasible for the quantitative analysis of iron oxides in CORBs. In actual practice, the accuracy of qualitative analysis of iron oxides must firstly be improved by the combination of XRD with DRS and then the choosing of quantitative analysis method can be achieved through the comprehensive analysis of both the predicted contents and crystalline of iron oxides. Related Articles | Metrics

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Recent Advancement in Methods of Estimating Geothermal Reservoir Temperature: A U.S. National Geothermal Data System-based Study JIANG Shu, CHEN Guohui, ZHANG Yuying, ZHANG Luchuan, KUANG Jian, LI Chun, CHENG Wanqiang Geological Journal of China Universities    2021, 27 (1): 1-17.   DOI: 10.16108/j.issn1006-7493.2020096 Abstract （563）      PDF （2072KB）（1147）       Knowledge map    Save Estimation of geothermal reservoir temperature plays a key role in the geothermal system research. This study employs geothermometers of geochemistry, mineral equilibria, mixing model with cold meteoric water, and gas to evaluate the reservoir temperature of different geothermal fields with data archived in the National Geothermal Data System (NGDS), which concludes the limitations of applications of different methods for determining the reservoir temperature and provides benchmarks for choosing the appropriate methods to calculate the geothermal reservoir temperature. The results reveal that: 1) The geochemical geothermometer method is reliable when the geothermal fluids reach the equilibrium between ions and minerals; the SiO2 (silica) geothermometer is more reliable than the cation geothermometer when the geothermal fluids have not reached the equilibrium; 2) The saturation index of the mineral equilibria can provide benchmarks choosing the geothermometers even if it cannot calculate the accurate reservoir temperature due to the selection of limited saturated minerals. For example, the chalcedony geothermometer is better than SiO2 geothermometer to estimate the reservoir temperature of due to the oversaturation of silica based on the multi-mineral equilibrium plot. For the vapordominated high temperature geothermal reservoirs, the minerals and ions cannot reflect the properties of geothermal reservoir, and the gas thermometer will be more successful in predicting the subsurface temperature in high-temperature geothermal systems. The mixing models usually overestimate the reservoir temperature since they pick up the temperature before the hot water gets mixed with the cold water. There is no universal geothermometer since each method has its own assumptions and works for specific geothermal setting. The best approach is to employ various suitable geothermometers and validate the results. Related Articles | Metrics

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Classified Evaluation of Shale Reservoirs in the Ordovician Wufeng to Silurian Longmaxi Formations in the Southern Sichuan Basin GUO Jianlin，JIA Chengye，HE Dongbo，LI Lin，ZHU Hanqing，ZHOU Yi，LIU Chang Acta Metallurgica Sinica    2020, 26 (3): 323-332.   DOI: 10.16108/j.issn1006-7493.2019047 Abstract （552）      PDF （4500KB）（959）       Knowledge map    Save On the basis of resource evaluation and favorable area evaluation, this paper established a set of classified evaluation criteria for shale reservoirs in the Wufeng-Longmaxi Formations in the southern Sichuan Basin. The criteria for effective reservoir identification include porosity (Φ) greater than 3%, gas saturation (Sg) higher than 30%, density of rock matrix (DEN) below 2.7 g/cm 3, brittleness index (BI) over 40% and gas contents (Vt) higher than 1 m 3/t. These criteria can distinguish the reservoirs and non-reservoirs. Based on the conception of geological and engineering integration, gas contents (Vt) has been selected to characterize the resource foundation of shale reservoirs, which is positively correlated with porosity and organic matter abundance. The brittleness index (BI) positively correlating with siliceous and carbonate contents has been selected to characterize the compressibility. Gas contents and brittleness index can comprehensively characterize the geological and engineering characteristics of reservoirs. Effective shale reservoirs have been further divided into three types: Type I with gas contents over 4 m 3/t and brittleness index greater than 50%; Type II with gas contents lower than 4 m3/t or brittleness index less than 50%; Type III with gas contents from 1 m 3/t to 4 m3/t and brittleness index between 40%-50%. Reservoirs in the Wufeng Formation and the low member of the Longmaxi Formation have a good quality which mainly consist of Types I and II and locally Type III. According to the criteria established in this paper, evaluations for reservoir quality of horizontal drillings have been conducted, and correlations between penetration rate of Type I reservoir, testing production and estimate ultimate recovery (EUR) are positive. Horizontal wells with drilling efficiency of Type I reservoir over 50% have probability of 92% for testing production over 15×104 m3/d and the corresponding EUR exceeding 8000×104 m 3, meeting the requirements of economic development. Related Articles | Metrics

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One-stop Sharing and Service System for Geoscience Knowledge Graph ZHU Yunqiang, DAI Xiaoliang, YANG Jie, WANG Shu, SUN Kai, QIU Qinjun, LI Weirong, QI Yanmin, HU Lei, LYU Hairong, WANG Xinbing, ZHOU Chenghu Geological Journal of China Universities    2023, 29 (3): 325-336.   DOI: 10.16108/j.issn1006-7493.2023029 Abstract （1220）      PDF （7167KB）（631）       Knowledge map    Save As the most effective way of knowledge organization and service at present, knowledge graph has become the cornerstone of artificial intelligence and has been widely used in semantic search, machine translation, information recommendation and so on. In the era of big data, there is an urgent need of Geoscience knowledge graphs for integrating, mining and analysis of scattered, multi-source and heterogeneous Geo-data and its unknown knowledge intelligent discovery. To promote the construction and application of Geoscience knowledge graphs, the Deep-time Digital Earth (DDE) International Big Science Program has taken knowledge graph as its one of the core research contents since its launch in 2019. After more than three years of construction, DDE has built a large number of Geoscience knowledge graphs, and it strong needs one-stop sharing and service system of these knowledge graphs. Firstly, this paper introduces the content framework, composition as well as characteristics of the DDE knowledge graphs. On this basis, the design of the one-stop sharing and service system for the Geoscience knowledge graph is designed that include the design of the system functional and technical architecture. Finally, the development and operation environment & tools, and key technologies of the system are discussed in detail. The practice has proved that the system can effectively realize the one-stop sharing and open access of DDE knowledge graphs. Meanwhile, it sets an example for other fields or domains’ knowledge graph integrating and sharing systems. Related Articles | Metrics

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A Review of the Establishment Methods of Training Image in Multiple-point Statistics Modeling WANG Mingchuan, SHANG Xiaofei, DUAN Taizhong Geological Journal of China Universities    2022, 28 (1): 96-103.   DOI: 10.16108/j.issn1006-7493.2020049 Abstract （708）      PDF （1268KB）（812）       Knowledge map    Save Multiple-point statistics (MPS) modeling has been the research hotspot of reservoir modeling technology in recent years, and its practicability is restricted by training image. The quality of training image determines the accuracy and reliability of MPS modeling, and is a key factor for the successful application of MPS modeling. This study addresses the characteristics and significance of training image, and systematically introduces the establishment methods of training image creation from the definition, usage and instance, etc., including hand drawn, object-based simulation, 3D seismic information extraction or transformation, prototype- ased model, process-based simulation and 2D image method. Then, our study comprehensively compares the data sources, advantages and disadvantages of various training image creation methods, and discusses the problems caused by MPS modeling relying on training images. Combined with reviewing prior works and MPS modeling practice, the research direction of training image and its establishment methods in the future is pointed out, which provides reference for MPS modeling researchers and users, and provides some thoughts for improving MPS modeling methods. Related Articles | Metrics

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Advances on Surficial Geochemistry Database and Related Research XU Yijiang, LI Chenglong, TAN Haolin, SHENG Xuefen Geological Journal of China Universities    2021, 27 (1): 58-72.   DOI: 10.16108/j.issn1006-7493.2021003 Abstract （651）      PDF （2242KB）（1127）       Knowledge map    Save Surficial Geochemistry is an interdisciplinary study of the earth’s surface system, which is closely related to climate, environment, and human being. With the advent of the era of big data, surficial geochemistry is facing new opportunities and challenges. In order to provide reference for the construction of the big data platform of the Deep-Time Digital Earth Project (DDE), this paper conducts a preliminary investigation on the existing surficial geochemical data and databases. The results show that the surficial geochemical data have the characteristics of diversity and inter-disciplinal. Most data are lacking of standards and in an unstructured state; larger databases such as GEOTRACES and PANGAEA have relatively accepted data standards and data management experience; SISAL database has achieved key results in the task of data structuring; which are all worthy of further study. The works of surficial geochemistry big data science construction should be guided by research goals and needs, and by setting up corresponding scientific working groups as joined forces to promote the digitalization of surficial geochemistry discipline. Related Articles | Metrics

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Review on Application of Microbially Induced Carbonate Precipitation (MICP) for Soil Stabilization ZHOU Yingzheng, GUAN Dawei, CHENG Liang Geological Journal of China Universities    2021, 27 (6): 697-706.   DOI: 10.16108/j.issn1006-7493.2020116 Abstract （717）      PDF （1454KB）（791）       Knowledge map    Save Microbial mineralization is a recently developing new branch in engineering of soil improvement that deals with the application of microbiological activity to improve characteristics of soils. One of the most commonly adopted processes to achieve soil bio-cementation is through microbially induced carbonate precipitation (MICP). This technique utilizes the metabolic behavior of urease bacteria to induce calcite that binds the loose soil particles integrally, leading to increased mechanical properties of soils. This paper systematically introduces the study of MICP about mineralization mechanism of urease bacteria, relative treatment methods, influencing factors, derived new technique (EICP) and relative field trials in geotechnical engineering. The practicability of the MICP is summarized. Finally, the challenges and potential solutions of MICP engineering applications in the current research stage are briefly discussed. Related Articles | Metrics

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Geology and Geomorphology of Tarim Basin and Its Evolution in the Cenozoic LI Jianghai，WUTongwen，LEI Yuting Acta Metallurgica Sinica

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Progress of Methods for Assessing CO 2 Mineralization Storage Potential in Basalt GAO Zhihao, XIA Changyou, LIAO Songlin, YU Xiaojie, LIU Muxin, LI Pengchun, LIANG Xi, DAI Qing, HUANG Xinwo Geological Journal of China Universities    2023, 29 (1): 66-75.   DOI: 10.16108/j.issn1006-7493.2022099 Abstract （2022）      PDF （1109KB）（588）       Knowledge map    Save CO 2 geological storage is an important technology to reduce CO 2 emissions, which can safely store CO 2 in geological formations for millions of years. Conventional CO 2 storage reservoirs include deep saline aquifers and depleted oil and gas reservoirs. Basalt is a new type of CO 2 storage reservoir that has been attracting attention in recent years. CO 2 storage in basalt would increase the technical method and potential of CO 2 geological storage. Storage potential assessment is one of the fundamental works of CO 2 geological storage study. This paper systematically examines the current methods for assessing the storage potential of CO 2 in basaltic rocks, and analyzes the principles and application scenarios of various methods. Then, the study takes the basalt of Icelandic Active Rift zone as an example to compare each of the methods. The study suggests that the current CO 2 mineralization storage potential assessment methods generally include three categories: ① Unit rock storage potential assessment method, which evaluates carbon sequestration potential based on the reaction volume or area of rocks; ② Mineral replacement storage potential assessment method: based on the volume of minerals that can react with CO 2 in basalts. ③Pore filling storage potential assessment method, which evaluates the proportion of secondary minerals that can fill reservoirs’ pore space after CO 2 mineralization. The authors note that the first method requires special experimental analysis, making it more challenging, the second method is more appropriat for basalts with high porosity and low reactive mineral content, while the third method is more suitable for basqlts with low porosity and high reactive mineral content. Related Articles | Metrics

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Research Progress and Prospect of the Gangdese Magmatic Belt in Southern Tibet MENG Yuanku, YUAN Haoqi, WEI Youqing, ZHANG Shukai, LIU Jinqing Geological Journal of China Universities    2022, 28 (1): 1-31.   DOI: 10.16108/j.issn1006-7493.2020057 Abstract （648）      PDF （2414KB）（1044）       Knowledge map    Save The Gangdese magmatic belt is the product of the northward subduction of the Neo-Tethys oceanic lithosphere beneath the Lhasa terrane and subsequent India-Asia collision. The Gangdese magmatic arc belongs to the typical continental magmatic belt and is the target area for studying plate accretion, crustal growth and reworking and collisional orogeny. Numerous lines of evidence indicate that the Neo-Tethys oceanic lithosphere experienced four distinct stages of evolution: the early-stage subduction (>152 Ma), late-stage subduction (100 to 65 Ma), main-collisional (55 to 40 Ma), and post-collision extentional stages (23 Ma to present). Multiple studies were carried out in the Gangdese belt and much progress has been made during past decades. However, the formation and evolution of the Neo-Tethys Ocean and magma source of igneous rocks are still debated, especially the detailed petrogenetic dynamic processes. This paper reviews the evolution history and tectonic background, and then summarizes related scientific problems from thirteen aspects. It is shown that the Gangdese magmatic belt is a typical magmatism-tectonismmineralization-deformational metamorphism belt and experienced multi-stage evolution processes rather than a simple continental magmatic arc aggregated in the Lhasa terrane. The review shows that (1) the Gangdese magmatic belt is a natural laboratory for studying the evolution history of the Neo-Tethys, and provides better constraints on the styles of the subducting slab. (2) The different-stage granitoid stocks and batholiths might be formed by multiple additions and incremental assembly of magmas over a span of millions of years or even longer. Therefore, we should use a mush model to reconstruct petrogenesis and petrogenetic secnarios of granitoid rocks in detail. (3) The mantle nature of the Gangdese region shows complicated features that are characterized by geochemical heterogeneity along the arc strike direction. (4) The reversed isotopes exist in the Gangdese belt, probably indicating an ancient nucleus. (5) The Gangdese belt is tilting and has different crustal compositions that are characterized by lower crustal compositions in the eastern segment and middle-upper crustal compositions in the middle-western segment. Crustal tilting of the Gangdese region suggests a differential and imbalanced exhumation process. (6) At present, numerous studies are focused on igneous rocks with methods mainly including radioactive Sr-Nd-Hf isotopes, whereas non-traditional stable isotopes (Mg-O-Li-B-Mo) are rarely reported. In addition, research topics are mainly associated with petrogenesis and geochronology, but few studies focus on the magma emplacement and post-magmatic deformation and uplifting-denudation processes. (7) Research in structural geology of the area is few and usually tectonic evolution is inferred from magmatic evolution in the Gangdese belt, southern Tibet. Finally, we also provide future prospects based on the current research status of the Gangdese magmatic belt in southern Tibet. Related Articles | Metrics

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Status and Advances of Research on Caprock Sealing Properties of CO 2 Geological Storage CHEN Bowen, WANG Rui, LI Qi, ZHOU Yinbang, TAN Yongsheng, DAI Quanqi, ZHANG Yao Geological Journal of China Universities    2023, 29 (1): 85-99.   DOI: 10.16108/j.issn1006-7493.2023010 Abstract （1535）      PDF （6425KB）（595）       Knowledge map    Save CO 2 Geological storage is one of the key technologies to address global climate changes and reduce greenhouse gas emissions. Large-scale CO 2 injection into the formation is prone to inducing CO 2 leakage problem. In particular, the leakage problem of CO 2 through caprock includes capillary leakage, hydraulic fracture and leakage along pre-existing faults crossing caprock. Therefore, evaluation of caprock seal is crucial for prediction of long-term safety and stability of CO 2 geological storage. This paper provides an overview of the current status of research on sealing mechanisms, influencing factors, and damage modes affecting caprock seal of CO 2 geological storage. It is concluded that caprock seal mechanisms include capillary seal, hydraulic seal, and overpressure seal. The main influencing factors of caprock seal characteristics include caprock lithology, mudrock-sand ratio, caprock mechanical properties, and sequestration pressure. Then, the damage modes of caprock seal during CO 2 injection are illustrated, and some insight into the shortcoming of caprock seal is provided. Related Articles | Metrics

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Marine Redox Fluctuation during the Early Cambrian Age 10: Evidence from U Isotopes QIU Chen, WEI Guangyi, MIN Siyu, CHEN Xi, LING Hongfei Geological Journal of China Universities    2022, 28 (1): 40-50.   DOI: 10.16108/j.issn1006-7493.2020038 Abstract （543）      PDF （2251KB）（751）       Knowledge map    Save The marine animal diversity was generally low during late Cambrian and early Ordovician. Biogeochemical studies suggest that it may have been related with fluctuations in oceanic redox conditions, despite still lack of evidence. Well-preserved marine carbonates could record the geochemical characters of ancient seawater, and their uranium isotope compositions (δ238U) can be used to reconstruct the global oceanic redox conditions. In this study we analyzed the uranium isotope compositions of marine carbonates of the basal Cambrian Stage 10 from Wa’ergang section, South China. Our data show that the δ238U profile has three negative excursions with minima of -0.8‰ , -0.55‰ and -0.60‰ , respectively, which indicates three intervals of oceanic anoxia expansion. Modeling results based on the uranium isotope mass balance model suggest that about 22%, 3.5% and 5% of the global sea-floor were covered by anoxic water during these three intervals, respectively. We speculate that the first anoxic interval may have been related with increase in primary productivity due to enhanced weathering input of nutrients, and the latter two may have been induced by upwelling of deep anoxic water during the transgressions. Related Articles | Metrics

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Genesis of Alkali-Feldspar Granite at Dawangshan Tungsten Polymetallic Ore Concentration Area in Central Jiangxi Province: Constraints from LA-ICP-MS Zircon U-Pb Chronology and Geochemistry YANG Qingkun，GUO Fusheng，YU Yushuai，ZHANG Xiaoliang，HUA Chen Acta Metallurgica Sinica

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Enzyme-induced Calcium Carbonate Precipitation (EICP) and Its Application in Geotechnical Engineering CAO Guanghui, LIU Shiyu, YU Jin, CAI Yanyan, HU Zhou, MAO Kunhai Geological Journal of China Universities    2021, 27 (6): 754-768.   DOI: 10.16108/j.issn1006-7493.2020200 Abstract （1821）      PDF （4975KB）（1342）       Knowledge map    Save The technique of improving soil by enzyme-induced calcium carbonate precipitation is called EICP, which has attracted more and more attention over the past decade due to its wide application. The article describes the mechanism of EICP and summarizes the extraction methods of plant urease and bacterial urease. In addition, the influence of factors such as urease, calcium source, urea, skimmed milk powder, temperature and pH on the cementing effects of EICP is explored. Furthermore, methods for testing the strength, calcium carbonate content, microstructure and composition of EICP reinforced samples are summarized, and the application of EICP in geotechnical engineering is evaluated. The purpose of this article is to summarize the current status of EICP research and potential problems that need to be overcome in future research. Related Articles | Metrics

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Organic Geochemistry of Organic-rich Cherts in the Middle Permian Gufeng Formation in Chaohu, Lower Yangtze Area GENG Zi’ao，WEI Hengye Acta Metallurgica Sinica    2019, 25 (6): 823-.   DOI: 10.16108/j.issn1006-7493.2019082 Abstract （360）      PDF （4579KB）（692）       Knowledge map    Save The black cherts in the middle Permian Gufeng Formation in Chaohu area in Lower Yangtze, South China are rich in organic matter. This formation is the potential source rocks of petroleum and shale gas exploration in China. The study on the organic matter accumulation of the Gufeng Formation is important for the petroleum exploration. Here we analyze total organic carbon (TOC) content and biomarkers characteristics of organic matter in the Gufeng cherts of middle Permian in the Pingdingshan, Chaohu area, so as to address the organic matter accumulation mechanism. Our results show that the organic matter thermal mature proxy C29 ααα 20S/(20S+ 20R) ratios range from 0.37 to 0.46, and C31 22S/(S+R) ratios range from 0.53 to 0.59. These suggest that the thermal mature level is the early stage of“oil window”. The n-alkane compounds are mainly composed of short-chain n-alkanes and peak at C18. Hopane contents are higher than the terpane. C27 ααα 20R sterane is higher than the C28 and C29 ααα 20R. These suggest that the organic matter of the Gufeng Formation originates from phytoplankton algae and bacteria with a small amount of terrestrial high plant. The Pr/Ph ratios of the organic matter in the Gufeng Formation is less than 0.6, and the average gamacerane index is 0.2. These suggest that the redox conditions of paleo-water column during the deposition of the Gufeng Formation were moderate stratification and anoxia. The organic-rich Gufeng Formation is probably related to this stratification and anoxia during warm climatic conditions. Associated with the suddenly cooling, enhanced upwelling increased greatly the primary productivity greatly and yielded more large-scale organic matter accumulation. Related Articles | Metrics

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LA-ICP-MS Zircon U-Pb Dating, Geochemical Characteristics and Tectonic Significance of Jundong Granites in Northeastern Guangxi GAO Aiyang, SHI Yu, LIU Xijun, ZHAO Zengxia, LIU Minghui, HUANG Chunwen, Geological Journal of China Universities    2022, 28 (2): 225-239.   DOI: 10.16108/j.issn1006-7493.2021021 Abstract （289）      PDF （5071KB）（708）       Knowledge map    Save The Jundong granitic pluton is located in the southwest of the Qin-Hang belt, with the rock combination of dioritetonalite-granodiorite. In this study, we present LA-ICP-MS zircon U-Pb ages of granitic rocks from the Jundong pluton, the crystallization age of the Jundong rock body is 423-430 Ma, belonging to the Caledonian period. The rocks have lower SiO 2 contents of 55.47-62.95 wt%. One of the samples belongs to the shoshonite series and the others are high-K calc-alkaline series. The A/CNK values are 0.70-1.18, showing as quasi-aluminous or peraluminous rocks. The rocks are enriched in large ion lithophile elements (LILE, e.g., Rb, Ba, Th and U) and relatively depleted in high field strength elements (HFSE, e.g., Nb, Ta, Sr, P and Ti) relative to primitive mantle. The Jundong granitic pluton are mixing products of different original rock sources and formed in the intracontinental collisional orogenic tectonic environment. Related Articles | Metrics

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Influence of Subducting Plate Dynamic Properties to Flat-slab Subduction by Numerical Modeling ZHU Zhiyuan, WU Benjun Geological Journal of China Universities    2021, 27 (2): 240-248.   DOI: 10.16108/j.issn1006-7493.2019110 Abstract （460）      PDF （1886KB）（686）       Knowledge map    Save This particular phenomenon of flat-slab subduction mainly occurs in South American, which is closely related to the structural geological phenomena such as earthquakes and volcanoes in this area. However, mechanics of flat-slab subduction is not yet well understood. By numerical modeling, we investigate influences of subducting plate dynamic properties to the geometry of flat-slab subduction. The model results show that subducting plate thickness and density contrast between slab and mantle have great impacts to flat-slab formation. The appropriate slab thickness (around 70 km) facilitate slab flattening, while thicker slab is difficult to bend and hesitates to flatten. The smaller the density anomaly of subducting plate, the easier slab flattens and the longer flab-slab length. When density anomaly is very large, no flat-slab is predicted. In addition, strong plate promotes flat-slab formation. Flat-slab length increases with plate viscosity increasing. We also find that trench rollback velocity decreases during the slab flattening episode. Our reference model REF_MODEL has comparable flat-slab geometry with central Chile subduction, which provides the insight of flat subduction formation in this area. Related Articles | Metrics

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Macroscopic and Mesoscopic Investigation on the Physical and Mechanical Characteristics of Coral Limestone at Different Depths MA Linjian, LIU Huachao, ZHANG Wei, LI Qi, ZHU Honghu, WU Jiawen Geological Journal of China Universities    2023, 29 (3): 471-478.   DOI: 10.16108/j.issn1006-7493.2021074 Abstract （1070）      PDF （2519KB）（469）       Knowledge map    Save In order to investigate the physical and mechanical characteristics of coral reefs with different depth in the South China Sea, scanning electron microscopy (SEM) and X-ray tomography (CT) technology are used to characterize the micro morphology and internal pore structure characteristics of shallow and deep reef limestone. Quantitative relationships between P-wave velocity and porosity as well as density were established. Uniaxial compression tests on dry and saturated reef limestone were also carried out. Results show that shallow reef limestone is porous with excellent pore connectivity, and the main mineral composition is aragonite, which belongs to the biological sedimentary rock. While deep reef limestone is dense with poor pore connectivity, and the main mineral composition is calcite, belonging to the metamorphic rock. The porosity of deep reef limestone is about 1/10, with an average peak compressive strength of about 4.8 times and an average elastic modulus of about 4.5 times that of shallow reef limestone. Reef limestone belongs to soft or extremely soft rock, characterized by brittle destruction property. The typical damage pattern is multiple rupture surface destruction along the primary pore, growing line of corals and weak bond surface, with high  residual strength. The hydrogenic effect of reef limestone is significant, and the water rationality of deep reef limestone is stronger than shallow reef limestone. The significant difference of physical and mechanical performances in shallow and deep reef limestone are mainly due to the variety in mineral components, pore structure and lithology caused by the varying degree of rock cementation with different depths. Related Articles | Metrics

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Characteristics of Cryptoexplosive Breccia from the Chating Copper-Gold Deposits, Xuancheng, Anhui Province and Its Metallogenic Significance XIE Qiaoqin，SUN Rui，XU Xiaochun，XU Xinyue，AN Yuhua，QIAN Shilong Acta Metallurgica Sinica    2020, 26 (3): 255-264.   DOI: 10.16108/j.issn1006-7493.2019045 Abstract （1102）      PDF （6839KB）（746）       Knowledge map    Save The Chating copper-gold ore in Xuancheng region is a newly discovered large ore deposit in the Mesozoic-Cenozoic volcanic-sedimentary Nanling-Xuancheng basin in recent years, where the deposits are located at shallow depths of the Middle-Lower Yangtze River. This study is focused on the cryptoexplosive breccia pipe developed in the intrusives of quartz-dioriticporphyrite in the Chating copper-gold ore deposits. Based on the detailed core observations and petrographic analysis, characteristics and types of cryptoexplosive breccia are determined, and the relationship between the cryptoexplosive breccia and the copper-gold mineralization is discussed. The cryptoexplosive breccia in the ore deposits can be divided into three types: cryptoexplosivemelt-crystal-lithicbreccia, cryptoexplosive hydrothermal breccia, and cryptoexplosive fracture breccia based on its textures, compositions and abundance of rubbles. The cryptoexplosive breccia appears as an irregular pipe enveloped by the quartz-dioriticporphyrite and shows a regular spatial distribution. From the center of breccia to wall-rock are quartz-dioriticporphyrite, cryptoexplosivemelt-crystal-lithicbreccia, the cryptoexplosive hydrothermal breccia, and the cryptoexplosive fracture breccia, respectively. The spatial relationship between the alterated, mineralized and the cryptoexplosive breccia pipe shows that there exists a genetic link between formation of cryptoexplosive breccia and mineralization. The cryptoexplosion of the melt, liquid and gas originated from intermediate-acid magma induced the formation of large amount rubbles and fractures which can cause sudden temperature and pressure changes of ore-forming fluids. In addition, the cryptoexplosive breccia may provide room for migrating, mixing, and ore-forming material unloading for ore-forming hydrothermal fluid that arose from magmatic hydrothermal fluid. The geological features of the Chating copper-gold deposit are similar to those of the porphyry deposits including the intermediate-acid porphyrite host rocks, the alteration types, and zonation of wall rocks, as well as fine-grained dissemination and fine-veined, and net-veined mineralization. However, the mineralization enrichment site is consistent with the cryptoexplosive breccia pipe. Also, the geological features such as breccia, veined, agglomerated mineralization and hydrothermal anhydrite developed intensively in the vein are distinctly different from typical porphyry deposits. Therefore, based on these characteristics, we suggest that the Chating copper-gold ore deposit is a cryptoexplosive breccia type deposit closely related to intermediate-acidic hypabyssal intrusion. Related Articles | Metrics

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Spatial-Temporal Distribution of Mesozoic Ore Deposits in South China and Their Metallogenic Settings MAO Jing-wen1, XIE Gui-qing1, GUO Chun-li1, YUAN Shun-da1, CHENG Yan-bo2, CHEN Yu-chuan1 J4    Abstract （3367）      PDF （5028KB）（5247）       Knowledge map    Save Based on extensive field investigation and precise geochronological data we proposed Mesozoic metallic mineralization in South China can be grouped into three pulses, i.e. Late Triassic (230~210 Ma), Mid-Late Jurassic (170~150 Ma), and Early-Middle Cretaceous (134~80Ma). The mineralization elements in these three pulses are different. The Triassic mineralization is Peraluminous granite-related W-Sn-Nb-Ta. The Mid-late Jurassic mineralization can be further divided into 170~160 Ma porphyry and skarn Cu and I-type granite-related Pb-Zn-Ag, and 160~150 Ma paraluminous granite-related polymetallic W-Sn. Although the Cretaceous mineralization lasted about 54 Ma, its peak ranged from 100 Ma to 90 Ma. The major types of the mineralization are epithermal Au-Ag-Cu and granite-related polymetallic tin (tungsten). The Triassic peraluminous granite-related W-Sn-Nb-Ta is a response to the post-collisional process of the South China plate with the North China plate. The Izanagi plate started to subduct beneath the Eurasian continent at ca. 180 Ma and then the porphyry copper deposits and vein type Pb-Zn-Ag deposits and their related I-type granitoids or aidakitic rocks formed when the subducted plate was teared up in several locations at 170~160 Ma.After then a big window occurred in the Nanling area, triggering the asthenospheric substance got into the upper crust so that developed large-scale high fractionation paraluminous granite and related polymetallic W-Sn mineralization. It was a relatively quiet period of 150~135 Ma in South China except for the Middle-Lower Yangtze River Valley area located in the northeastern margin of the South China plate. Because starting to change motion-direction to northeast the subucted plate was teared up along the Middle-Lower Yangtze River Valley which used to be a foreland basin of the Triassic Dabie-Sulu orogenic belt. A group of skarn-porphyry Cu-Mo-Au-Fe ore system and related I-type or aidakitic granites developed along the cross of the Middle-Lower Yangtze River Valley with the NE-trending faults at an age range of 145~135 Ma. From 135 Ma the subducted plate moved along several groups of regional-scale NE-striking fault zones comprising the Tan-Lu fault zone, which trigged the Eurasian continent to extensive extension. At the setting developed a lot of linear NE-trending Cretaceous faulting basins and metamorphic cores accompanied with volcanic rock eruption as well as epithermal Cu-Au-Ag ore system, granite-related polymetallic Sn (W) deposits and hydrothermal uranium deposits at age of 120~80 Ma with a peak of 100~90 Ma. Related Articles | Metrics

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An Overview of Characteristics and Prospecting of Gold Ore Deposits in China WANG Bin，LI Jingchao，WANG Chengxi，ZHENG Xiao，SUN Kefeng Acta Metallurgica Sinica    2020, 26 (2): 121-.   DOI: 10.16108/j.issn1006-7493.2019033 Abstract （562）      PDF （2571KB）（899）       Knowledge map    Save Based on the geodynamic settings of gold metallogenesis and the basic geological features of gold ore deposits, China’s gold deposits can be classified into 11 categories. Among these categories, the structurally-fractured altered-rock type, inner and outer contacting belts type of plutonic intrusives, the Carlin or quasi-Carlin type, hydrothermal type within low-grade metamorphic clastic rocks, and continental volcanic rock types are the types of interest in prospecting. As far as metallogenic ages concerned, those that occurred in Mesozoic and Cenozoic are the major types. According to their geotectonic units, geological evolution, metallogenic geological conditions, spatial-temporal distribution, gold deposit types, regional metallogenic factors, and volumes of mineral resources, totally 42 gold ore concentration areas, which are spatially distributed in clusters, have been preliminarily identified on the basis of China’s III-graded classification scheme of metallogenic zones (belts). According to gold prospecting borehole quantities per unit area, China’s gold ore concentration areas can be categorized into 3 levels, i.e., highly, moderately, and lowly developed. The highly developed ones are mainly distributed in Central and Eastern China. Except the placer gold deposits, about 88.12% boreholes for primary gold (rock gold or associated gold) deposits are less than 500 m with deep in China, suggesting that the quantities and depths of gold exploration drillings in China are less and shallower than in other countries. As for the gold resources exploration potentials, we propose that (1) in Central and Eastern China, the deep parts and the peripheries of the existing gold mines are key locations to be focused on; (2) for Western China, the gold ore concentration areas, which are located especially in Xinjiang Uygur Autonomous Region, Qinghai Province, and Tibet Autonomous Region, are the future key regions with immense potentials for unexplored gold resources. Related Articles | Metrics

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Experimental Investigation on the Interaction Between Calcite and Silica-bearing Fluid: Implications for the Formation of Silicified Carbonate Reservoir YANG Yuanxian, CHEN Qianglu, QIU Ye, YOU Donghua, WANG Xiaolin Geological Journal of China Universities    2021, 27 (2): 218-228.   DOI: 10.16108/j.issn1006-7493.2020017 Abstract （650）      PDF （2354KB）（700）       Knowledge map    Save Recent oil and gas exploration shows that silica-bearing hydrothermal fluid is an important acidic fluid in carbonate sequences. Knowledge on the interactions between silica-bearing fluid and carbonate rock is critical to understand the origin of the silicified carbonate reservoir and the prediction of reservoir distribution. In this study, experimental investigation was carried out on the interaction between calcite and silica-bearing fluid at temperatures ranging from 200 to 375℃ by using fused silica capillaries and hydrothermal reactor as the reaction chambers. In situ Raman spectroscopy was used to describe the process of the reaction. Besides, Scanning electron microscopy equipped with energy dispersive spectroscopy (SEM-EDS) was used to observe the morphology and to identify the composition of the quenched solids. Firstly, the temperature condition of the decarbonization reaction between silica-bearing fluid and calcite is revealed. Calcite reacts with silica-bearing fluids at temperatures above 275℃ to form CO 2, and the solid phase is non-wollastonite calcium silicate. The detailed structure of this calcium silicate needs further investigation. This result indicates that the dissolved silica itself cannot react with limestone at the reservoir temperatures. Secondly, the high salinity and the CO 2-bearing nature of the silica-bearing fluid are the important factors causing limestone dissolution. Finally, the presence of CO 2 can promote the precipitation of siliceous component, including quartz. Based on the above experiments, the formation of the silicified carbonate reservoir in the Shuntuoguole area of the Tarim basin is proposed, integrated with the previous studies. The silica-bearing hydrothermal fluid migrates upward along the deep and large faults, passing through the Sinian-Lower Ordovician dolomite layer, where the siliceous components will react with the dolomite to form magnesium-rich silicate and CO 2. CO 2 is an important acidic component, which is conducive to the dissolution of the shallow carbonate and the preservation of pores. Decrease in fluid temperature and pressure, and the presence of CO 2 result in the precipitation of quartz, forming large amounts of intercrystalline pores. Related Articles | Metrics

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High Precision Analytical Method for Stable Strontium Isotopes CHEN Xuqi, ZENG Zhen, YU Huimin, HUANG Fang Geological Journal of China Universities    2021, 27 (3): 264-274.   DOI: 10.16108/j.issn1006-7493.2021031 Abstract （1046）      PDF （922KB）（770）       Knowledge map    Save Because of the development of high-precision stable Sr isotope analytical method, stable Sr isotopes have been paid more attention in recent years. Great progress has been made in studies on supergene geochemistry, paleoenvironment, archaeology, endogenesis, and meteorites. This paper summarizes the key techniques of δ88/86Sr analytical methods. Ion exchange method with Eichrom Sr Specific Resin has been widely used to purify Sr. But this specific resin is expensive and may result in contamination during the chromatographic processes. Thus it could be replaced by cation-exchange resin. MC-ICP-MS and TIMS are the instruments for isotope measurement. Normally, MC-ICP-MS has higher measurement efficiency but slightly lower precision than TIMS. Standard-Sample-Bracketing method, Zr-Empirical-External-Normalization method, and double spike method are used to correct the instrumental mass bias. The Double Spike method may have relatively high measurement precision, but there are only a few studies using this method on MC-ICP-MS. Furthermore, there is no detailed comparison of δ88/86Sr of international standard materials. Therefore, optimizing the analysis process, improving the measurement precision, and more determination of δ88/86Sr of standard materials are necessary for the future studies of stable Sr isotopes. Related Articles | Metrics

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Hirnantian (latest Ordovician) Stratigraphy and Palaeogeography of the Western Yangtze Platform, South China WANG Guangxu, WEI Xin, CUI Yunong, ZHANG Xiaole, WANG Qian, ZHAN Renbin Geological Journal of China Universities    2023, 29 (2): 298-315.   DOI: 10.16108/j.issn1006- 7493.2022051 Abstract （1421）      PDF （20684KB）（435）       Knowledge map    Save Hirnantian (latest Ordovician) rocks and fossils have still not been sufficiently documented in the western Yangtze region of South China (today’s southwestern Sichuan and northeastern Yunnan provinces, Southwest China). Compilation of published and new data results in refined Hirnantian stratigraphy and palaeogeography of the region. The lower Hirnantian is typified by the dark-grey cacareous mudstone or argillaceous limestone of the Kuanyinchiao Formation yielding cool-water Transitional Benthic Fauna 1 (TBF 1). The middle Hirnantian strata, however, can be grouped into a near-shore lithofacies belt with distinctive grainstones of the upper Kuanyinchiao Formation yielding warm-water TBF 2, and a more offshore belt characterized by black shales of the basal Lungmachi Formation. A similar facies differentiation occurs in the upper Hirnantian of the region, but the near-shore sediments are in places represented by TBF 3-bearing calcareous siltstones, for which a new lithostratigraphic unit, the Weiba Formation, is proposed. On this basis, refined Hirnantian paleogeographic reconstructions of the western Yangtze Platform are presented. Related Articles | Metrics