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    Characteristics of the Guatemalan Feicui and Its Comparison to the Myanmar Feicui
    XING Biqian, SHI Guanghai, ZHANG Jinhong, LONG Chu, ZHANG Yu, HE Liyan, HU Rujie
    Geoscience    2021, 35 (06): 1769-1788.   DOI: 10.19657/j.geoscience.1000-8527.2021.23
    Abstract1886)   HTML89)    PDF(pc) (15989KB)(878)       Save

    Guatemala is the second largest producing area of feicui after Myanmar. The demand for the identification of feicui from the two origin areas is becoming more and more urgent, which is of great significance. The mineral composition, texture and structure characteristics of Guatemalan blue water jade were obtained by microscope observation, electron microprobe test and back-scattered electron images (BSE). Combined with the data of the tectonic environment, natural geographical environment, rough stone characteristics, and mineral composition characteristics of feicui from the two producing areas, a comparative analysis was made. The results show that compared with Myanmar jade, the weathered crust of the Guatemalan feicui is less rounded but thinner, with less granular tactile sensation, and little or almost no “red fog” from the skin inward. On the other hand, there are significant spherical weathering characters in the rough stones of Myanmar, the weathering crust is usually well rounded, thicker, and gritty to the touch. “Red fog” can be occasionally seen between the weathering crust and jade of the Myanmar feicui. The discriminant diagram of jadeite and omphacite composition shows the jadeite and omphacite from Guatemala appear relatively rich in Ca, and poor in Na, while the jadeite and omphacite from Myanmar are relatively poor in Ca, rich in Na. In terms of Fe content, the jadeite in the Guatemalan feicui is lower than that in the Myanmar feicui, while the omphacite in the Guatemalan feicui is higher than that in the Myanmar feicui. It can be used to distinguish the origin of feicui in actual production by comparing the appearance characteristics of feicui fully and analyzing the discriminant map comprehensively.

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    Hydrogeochemical Characteristics and Genesis of Zhuhe Hot Springs in Zhaojue, Sichuan Province
    LU Li, CHEN Yudao, DAI Junge, WANG Zhe, ZOU Shengzhang, FAN Lianjie, LIN Yongsheng, ZHOU Changsong
    Geoscience    2021, 35 (03): 703-710.   DOI: 10.19657/j.geoscience.1000-8527.2021.061
    Abstract649)   HTML22)    PDF(pc) (5161KB)(581)       Save

    Zhaojue, a national-level poverty-stricken county in Sichuan Province, is located in the extended Ganzi-Xinlong-Litang geothermal field. Revealing the geothermal heat cycling mechanism of Ganzi-Xinlong-Litang geothermal field in western Sichuan would help to alleviate local poverty and rationally develop and utilize geothermal resources. In this study, the Zhuhe hot springs in Zhaojue were analyzed for their hydrochemistry and H-O stable isotopes. The results show that the Zhuhe hot springs are HCO3-Na-type, whilst the temperature of the supply area is about 14.71 ℃, and the supply elevation is 3,345-3,560 m. The mixing model and the silicon-enthalpy model were used to estimate the proportion of cold water mixing in large hot springs, which yielded 77.00% and 75.95%, respectively. Similar estimation yielded 81.00% and 78.61%, respectively, for small hot springs. The depths of heat storage cycle were estimated to be 3,426.38-3,766.81 m. Formation of the Zhuhe hot springs are likely controlled by the Mufoshan and Zhuhe faults. During the deep geothermal circulation, the spring water likely mixed with shallow cold water and reacted with the wallrocks. The exposed surface formed the medium-low temperature geothermal resource centered on “large hot spring and small hot spring”.

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    Characteristics and Formation Mechanism of Strontium-rich Groundwater in Malian River Drainage Basin, Southern Ordos Basin
    LI Haixue, CHENG Xuxue, MA Yuekun, LIU Weipo, ZHOU Bin
    Geoscience    2021, 35 (03): 682-692.   DOI: 10.19657/j.geoscience.1000-8527.2020.037
    Abstract569)   HTML20)    PDF(pc) (6577KB)(548)       Save

    The Malian River drainage basin is located at the loess plateau in the southern Ordos Basin, in which the groundwater can be divided into the loess phreatic water, bedrock phreatic water and bedrock confined water based on the storage medium and burial conditions. Using 295 sets of groundwater hydrochemical data collected from 2015 to 2018, we analyze the Sr2+ concentration level, vertical and downstream distribution characteristics in the groundwater, and study the source and enrichment cause of Sr2+ in groundwater through factor correlation analysis. The results indicate that the groundwater Sr enrichment in the Malian River drainage basin is distinct, with the average Sr concentrations in the loess phreatic water, bedrock phreatic water, and bedrock confined water being 1.14 mg/l, 1.39 mg/l, and 5.24 mg/l, respectively. The Sr enrichment is mainly led by the water-rock interaction of Sr-bearing minerals. Major sources of Sr2+ in the loess phreatic water, bedrock phreatic water, and bedrock confined water are leaching from the carbonates and aluminosilicates, carbonates and sulfates, and carbonate minerals, respectively. The Sr2+ concentration in groundwater gradually increases along the flow direction, but varies with depth in different areas.

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    Geological Characteristics and Tectonic Evolution of Datong Basin
    LIU Airong, XU Yongjing, LIU Chenglin, PANG Ercheng
    Geoscience    2021, 35 (05): 1296-1310.   DOI: 10.19657/j.geoscience.1000-8527.2020.067
    Abstract1631)   HTML843)    PDF(pc) (21138KB)(522)       Save

    Integrating the tectonic evolution and control, and geological characteristics (e.g., structure and thickness) of the sedimentary sequence, the sedimentary facies and environment of the Datong basin are summarized. It is suggested that the Datong basin was formed in the Early Mesozoic (end Late Jurassic to Early Cretaceous), and its tectonic evolution comprises three stages: fault depression formation, half-graben development, and basin formation. This area was not only filled with tectonic layers during the three periods, but also developed faults in the early of Cretaceous, early deposition of Baode Formation and late deposition of Nihewan Formation. Besides five unconformities was showed in the field survey. In the Datong basin and its surrounding areas, EW-trending fold structure likely existed before the Yanshanian movement, and NW-directed compression may have superimposed on the EW-trending structure after the movement. After that, despite strong denudation, the Late Paleozoic and Mesozoic strata remained in the superimposing synclinal nuclei of the EW- and NE-trending folds.

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    Failure Mechanism of the Changhe Landslide on September 14, 2019 in Tongwei, Gansu
    WANG Haojie, SUN Ping, HAN Shuai, ZHANG Shuai, LI Xiaobin, WANG Tao, XIN Peng, GUO Qiang
    Geoscience    2021, 35 (03): 732-743.   DOI: 10.19657/j.geoscience.1000-8527.2020.073
    Abstract1178)   HTML41)    PDF(pc) (20609KB)(485)       Save

    A large loess landslide occurred in Xiaozhuang Village (Tongwei, Gansu Province) at around 11:00 am on September 14, 2019. About 800×104 m3 of a historical sliding mass was reactivated by rainfall, and slipped down along a weak interface. The sliding mass destroyed several roads and the Yangpo bridge. Preliminary estimation of 2,975 people in one township and two villages of Tongwei County were affected, causing a direct economic loss of 23.47 million yuan in agriculture, water conservancy, power supply, and infrastructure. Based on site investigation, unmanned aerial vehicle photography and numerical simulation, the deformation and failure characteristics of this landslide are described in detail, and the failure mechanism are preliminarily assessed. The main factor that affected the slope stability is the post-seismic interaction of rainfall and creep, and the failure process comprise five stages: pre-earthquake, earthquake damage, creep weakening, rainfall triggering and final sliding. Sinkholes and underground rivers were well developed in the slope, and represent the key control of the landslide boundary. Strong deformation and failure occurred at the trailing and leading edges of the landslide, but the deformation in the middle was relatively weak. We infer that the landslide was a traction-movement composite one controlled by topography and ground water. Understanding the conditions and mechanism of the Changhe landslide is hugely important for the early identification and risk prevention of similar landslides in the loess region of northwestern China.

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    Geochemical Characteristics and Genesis of the Longwangmiao Graphite Deposit in Xixia County,North Qinling
    YAN Kun, YANG Yanwei, WANG Liwei, ZHU Rongbin, LU Yunshen, ZHAO Hui
    Geoscience    2021, 35 (03): 589-598.   DOI: 10.19657/j.geoscience.1000-8527.2021.03.01
    Abstract535)   HTML28)    PDF(pc) (4465KB)(430)       Save

    The Longwangmiao graphite deposit in Xixia is located in the southern branch of the eastern Zhuyangguan-Liuquanpu graphite metallogenic belt in the North Qinling Mountains. The orebody occurs in the middle-deep regional metamorphic rock series of the Paleoproterozoic Qinling Group, and the original rock belongs to the terrigenous clastic rock-carbonate sandwiched basic volcanic rock sedimentary formation. The orebody is layered and quasi-layered, and the local occurrence is lenticular. The ore structure is mainly scaly, and a small amount of ore is disseminated or massive. The ore is mainly composed of calcite marble containing graphite (ribbon). The major elements are characterized by low Si, low Al, low alkali, high CaO and high LOI. The analysis of trace elements shows that large ion lithophile elements such as Rb, U, Th, La and Sm are enriched, while high field strength incompatible elements such as Ba, Nb and Ti are deficient. The Sr/Ba ratio ranged from 0.55 to 3.30, with an average of 2.07. The Rb/Sr ratio ranged from 0.02 to 1.15, with an average of 0.28. The content of ∑REE is on the high side, the differentiation degree of REE is high, the LREE is richer than HREE, and the negative anomalies of Eu and Ce are obvious, indicating that the protolith of the graphitic metamorphic rock series may have been formed in the marine tectonic environment of the passive continental margin. Comprehensive analysis shows that the Xixia Longwangmiao crystalline graphite deposit is an organic genetic regional metamorphic crystalline graphite deposit with obvious characteristics of superimposed heating metamorphism and tectonic transformation in the later stage of deposit formation.

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    Research on the Spatiotemporal Variation of Carbon Storage in the Coastal Zone of Liaoning Province Based on InVEST Model
    ZHU Liya, HU Ke, SUN Shuang, LIU Yuhan, LIANG Jiaxin
    Geoscience    2022, 36 (01): 96-104.   DOI: 10.19657/j.geoscience.1000-8527.2021.163
    Abstract928)   HTML40)    PDF(pc) (6792KB)(413)       Save

    The carbon storage of terrestrial ecosystem is closely related to global climate change. Studying the impact of land use change on the carbon storage of ecosystem services in the coastal zone is of great significance for regional ecosystem protection and economic and social development. Taking the coastal zone of Liaoning Province as an example, this paper analyzed the characteristics of land use change in coastal zone from 1995 to 2018, and used the carbon storage module of InVEST model to estimate the changes of regional carbon storage from 1995 to 2018. The results showed that: (1) the carbon storage of ecosystem in the study area showed a decreasing trend, with a cumulative decrease of 12.97×106 t; (2) the areas with high carbon storage are mainly distributed in the east and west sides and swamps in the middle of the study area, and the areas with low carbon storage are mainly distributed in the east of Jinzhou city and the north of Panjin city; (3) forest and cropland are the most important land use types for carbon sequestration in the study area, and its’s carbon storage accounts for 83.86% of the total carbon storage of all land use types. The increase of built-up land area and the decrease of forest and grassland area are the main reasons for the decrease of regional ecosystem carbon storage.

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    Middle Neoproterozoic Tectonic Evolution of the Mianlue Tectonic Belt: Evidences from Detrital Zircon U-Pb Geochronology and Geochemistry of the Guantianmen Metasedimentary Rocks in Lueyang County
    WANG Zhaoyang, PEI Xianzhi, LI Ruibao, PEI Lei, LI Zuochen, LIU Chengjun, ZHAO Shaowei, WANG Meng, CHEN Youxin, ZHOU Hai, ZHAO Jie, XU Lili
    Geoscience    2022, 36 (03): 770-795.   DOI: 10.19657/j.geoscience.1000-8527.2022.015
    Abstract219)   HTML15)    PDF(pc) (11669KB)(389)       Save

    A suite of greenschist to lower-amphibolite-facies metasedimentary rocks is exposed at Guantianmen in the Mianlue tectonic belt, and is characterized by intense ductile deformation. The depositional ages and tectonic settings of these rocks have long been controversial, which limits our understanding on the regional tectonic evolution. To constrain their depositional ages and tectonic settings, we conducted petrology, petrogeochemistry, and LA-ICP-MS detrital zircon U-Pb dating on the metasedimentary rocks. The results show that protoliths of the Guantianmen metasedimentary rocks are a set of fine-grained clastic rocks with local carbonate interbeds. Our work indicates that the metasedimentary rocks have undergone low-degree chemical weathering and sedimentary recycling, and were mainly derived from felsic to intermediate igneous rocks with continental arc signature. Two samples yielded similar age distributions, displaying a dominant ca.880-800 Ma age group with a main age peak at ca.830 Ma. The youngest age group is 747-736 Ma(avg.742±6 Ma). Combined with previous work, we suggest that the main provenance region of the Guantianmen metasedimentary rocks is the Early-Middle Neopro-terozoic magmatic arc in the Bikou and Hannan-Micangshan microblocks. The depositional age of the Guantianmen metasedimentary rocks should be later than 720 Ma. The rocks were most likely deposited in an extensional rift system during the middle-Late Neoproterozoic, in response to the Rodinia supercontinent breakup.

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    Geochemical Characteristics and Genesis of Pinghe Crystalline Graphite Deposit in Sichuan Province
    XIA Jinsheng, SUN Li, ZHANG Peng, CHEN Changkuo, WANG Junzhu, SI Jiangfu
    Geoscience    2022, 36 (06): 1486-1496.   DOI: 10.19657/j.geoscience.1000-8527.2022.06.04
    Abstract223)   HTML6)    PDF(pc) (6553KB)(389)       Save

    The Pinghe scaly graphite deposit,one of the crucial graphite deposits in China,located on the Micangshan-Dabashan thrust belt of upper Yangtze Block.Field survey,mineralogical and geochemical analysis of graphite bearing metamorphic rocks were carried out to study the ore genesis of this deposit.The ore bodies are hosted in the Mawozi Formation of the Mesoproterozoic Huodiya Group.The ore bodies which conform to the wall rocks mainly display bedding to lenticular occurrence.The host rocks of the deposit are mainly graphite schists and minor graphite bearing dolomotic marbles.The average fixed carbon content of the ore bodies is 16.32%.Graphites in the ore bodies mainly show flake textures with big flakes (>0.15 mm) of 37% and small to middle flakes (<0.15 mm) of 63%.The analysis on major and trace elements indicates that the protolith of the graphite-bearing schist has affinity to terrigenious argillaceous siltstone.Zircon SHRIMP U-Pb dating yields the metamorphic age of the graphite-bearing schist at (751.6±4.5) Ma.The δ13C of graphites averages on -24.17‰,which indicates the genesis of graphite in the deposit is mainly attributed to organic carbon.Therefore,we infer that the formation of the Pinghe deposit is closely linked to an organic origin and regional metamorphism.

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    Provenances and Tectonic Significance of Detrital Zircons from the Triassic to Jurassic Sedimentary Rocks in the Diancangshan Metamorphic Massif, Western Yunnan Province
    CHEN Jing, LI Dapeng, KANG Huan, GENG Jianzhen, ZHANG Jingjing
    Geoscience    2021, 35 (04): 883-913.   DOI: 10.19657/j.geoscience.1000-8527.2021.04.01
    Abstract602)   HTML25)    PDF(pc) (12983KB)(389)       Save

    The formation and evolution of the Ailaoshan ocean (AO), a branch of the Paleo-Tethyan ocean, has been precisely depicted via deciphering the magmatic records in the Sanjiang area, western Yunnan. However, regional sedimentary records that responded to the subduction and closure of the AO have still not been fully understood. Therefore, an integrated study has been carried out on 255 detrital zircon grains including U-Pb dating and analyses of trace element concentrations and Lu-Hf isotopic compositions from three sedimentary samples in the Diancangshan metamorphic terrane (DMT) in the Ailaoshan tectonic belt (ATB). Together with previously study, regional sedimentary records during the last stage evolution of the AO has been delineated. The weighted mean ages of the youngest igneous zircon groups of metamorphic sandstone DC1801, schist DC1703, and carbonate DC1702 are ~180 Ma, ~247 Ma, and ~254 Ma, respectively. Together with their field contact relationships and regional sedimentary correlation, the oldest depositional ages of these sedimentary rocks are restricted to the Early Jurassic (DC1801) and Early Triassic (DC1702 and DC1703). Provenance analyses show that different igneous rocks with ages of ~0.8 Ga, ~0.45 Ga, and ~0.25 Ga in the ATB and the late Grevillian (~0.95 Ga) and Pan-African (~0.6 Ga) igneous materials in the Indian continent before dispersion of the Indochina block from Gondwana were the main inputs for the Triassic clastic sedimentary rock (DC1703). In contrast, the Indosinian igneous rocks in the Simao block were the main inputs for the Jurassic clastic sedimentary rock (DC1801), while contributions of the ~0.45 Ga, ~0.8 Ga and ~0.95 Ga materials were largely depressed. Carbonates and coeval clastic sediments in the same depositional basin show similar detrital zircon U-Pb age distribution patterns, but signals that represent for far sourced materials notably decreased in carbonates. Evolution of the Hf isotopic compositions through time verified that the closure of the AO was at ~247 Ma. The sedimentary sequences of marine carbonate and continental clastic rocks (i.e., schist) documented the last stage evolution and closure of the AO. The Eu/Eu* values of these detrital zircon grains unravel regional crustal thickening from the closure of AO at ~247 Ma to ~235 Ma. The shift of the source areas from the Triassic to the Jurassic probably resulted from the uplift of the depositional areas due to the closure of the AO.

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    Genetic Model, Outbreak Features and Prevention of Post-seismic Deep-cut Trough-type Debris Flow: An Example from Yazhagou of Jiuzhaigou, Sichuan Province
    ZHANG Luming, YANG Dong, ZHOU Yong, LIU Peng
    Geoscience    2021, 35 (03): 744-752.   DOI: 10.19657/j.geoscience.1000-8527.2020.034
    Abstract466)   HTML6)    PDF(pc) (17090KB)(367)       Save

    Taking the Yazhagou debris flow in Jiuzhaigou earthquake area of Sichuan as an example, the outbreak features, the critical rainfall and the origin are studied in detail through geological surveys and historical data analysis. Based on the analysis of the formation cause, the corresponding prevention and control schemes are proposed. The results show that the debris flow is featured by being concealed, sudden, and destructive, with strong sediment transport capacity. The critical rainfall of debris flow outbreak is only half of that before the 12th May Wenchuan Earthquake, and no debris flow was reported in this area since 2014, indicating that the critical rainfall has a gradual recovery trend. Short bursts of heavy rainfall, deep-cut trough-type material supply, and elevated-steep topography are the root causes of the debris flow outbreak. The debris-flow genetic model includes the components of rainfall seepage, saturated rock and soil, mountain flood impact, deep-cut trough, headward erosion, scour erosion, bank erosion collapse, suspension and rolling. Controlling of Yazhagou debris flow in the earthquake area requires the protection standard and optimization of the control structure. Effective prevention and controlling method require mainly source control supplemented with debris obstruction. Our findings provide reference for the prevention and early warning of similar debris flows across the region.

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    Cadmium Bioavailability and Influencing Factors of Soil-rice System in Nanliujiang Catchment of Guangxi
    SHAO Yuxiang, YANG Zhongfang, WANG Lei, ZHUO Xiaoxiong, ZHANG Qizuan
    Geoscience    2021, 35 (03): 625-636.   DOI: 10.19657/j.geoscience.1000-8527.2021.03.04
    Abstract415)   HTML11)    PDF(pc) (4090KB)(345)       Save

    The alluvium soil in the Nanliujiang Catchment had the characteristics with low Cd contents in soils but high Cd contents in the rice seeds grown in there. In order to understand the distribution and transfer of Cd in the soil-rice system of the Nanliujiang Catchment, We collected rice and soil samples from different parent material in this region and analyzed the rice Cd and soil Cd, pH, Corg, N, S, Mn and oxides. Meanwhile, seven-step sequential extraction experiments were performed on some of the soil samples to find the representative bioavailability of Cd in soil-rice system. The results showed that compared with different parent soils, the Cd contents of the soils in order for the limestone soils>the upstream alluvium soils>the midstream alluvium soils>the downstream alluvium soils>the clasolite-produced soils, which was contrary to the order of Cd contents in rice seeds grown in these areas, and no significant correlation was observed between Cd contents in rice seeds and in cultivated soils (r=-0.030,p=0.84). It was revealed that total soil Cd content cannot represent bioavailable Cd content absorbed by rice. Water-soluble Cd in the soil was thought to be the main species in Cd translocation from soil to seed, according to its significant correlations between them. With the increase of soil pH, CaO, Mn, and soil organic carbon (Corg), the proportion of water-soluble Cd decreased significantly(r=0.12-0.45). This information may be of great significance for proposing effective measures to reduce the Cd contents of rice in the Nanliujiang Catchment.

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    Site Selection Strategy for An Annual Million-Ton Scale CO2 Geological Storage in China
    WANG Zijian, TANG Xuan, JING Tieya, YOU Mingxin, ZHANG Jinchuan, LI Zhen, ZHOU Juan
    Geoscience    2022, 36 (05): 1414-1431.   DOI: 10.19657/j.geoscience.1000-8527.2022.044
    Abstract358)   HTML18)    PDF(pc) (4500KB)(339)       Save

    CO2 geological storage are very important technology for the sustainable development for the industries with difficulties in reducing CO2 emissions. Compared with some countries that have succeeded in large CO2 geological storage projects with storage capacity of over a million tons per year, China’s CO2 geological storage projects are still in early stage, most projects in the size of 100,000 tons per year. China still lacks experience in CO2 storage site selection, injection and monitoring of large(>1 m tons CO2/year) CO2 geological storage projects. We classify the storage space into two types in term of their geological type, e.g. structural traps (anticline, fault and fracture) and lithologic traps (sandstone and carbonate reef). Based on the study of 15 large CO2 geological storage projects around the world, four classes of indices for site determination were summarized, storage size, injecting capacity, safety and economic evaluation. The site selection principle and parameters for CO2 geological storage sites with an annual storage capacity of one million tons are defined. In terms of basin types and geological characteristics of China, different CO2 storage strategies need to be adopted. For instance, for large cratonic basins, such as the Ordos and Songliao basins, which contain wide distribution of sandbodies, and large-scale anticline and lithologic traps, they provid the potential for large-scale deep saline aquifers or depleted petroleum reservoir storage site. For the fault-bound basins such as the Bohai Bay and China offshore basins, well-developed faults or fault-related traps provide only small storage capacity and they are easily influenced by sealing effectiveness. It is thus necessary to adopt the strategy of comprehensive evaluation of trap groups with dynamic evaluation of fault activity; as for the superimposed basin in western China, the structural thrust belts on the basin margin have generally intensive tectonic stress, and great difficulty in CO2 injection. This brings high risk for CO2 injection and storage. Instead, the paleouplifts and slopes in the basin center may represent effective storage sites. Therefore, the evaluation strategy for basins in western China would need to consider zoning and stratification.

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    Formation Mechanism of the Conjugate Strike-slip Faults in Tabei Uplift
    HUANG Shaoying, SONG Xingguo, LUO Caiming, NENG Yuan, MA Xiaodan, QI Jiafu, CHEN Shi
    Geoscience    2021, 35 (06): 1797-1808.   DOI: 10.19657/j.geoscience.1000-8527.2021.188
    Abstract398)   HTML5)    PDF(pc) (18712KB)(326)       Save

    Two sets of permeable X-type strike-slip faults (NNE- and NNW-trending) intersecting at a small angle (40°) are developed in the Tabei uplift of the Tarim basin. Based on the interpreted 3D seismic data in the Harahartang area of northern Tarim Basin, we studied the geometric distribution characteristics and profile deformation characteristics of strike-slip faults (focusing on the RP6 and HA13 faults), and analyzed and compared the differences of deformation and development characteristics of NNW-trending and NNE-trending faults. Based on the gravity and magnetic data from the basin and the activity characteristics of the surrounding orogenic belt, the development mechanism and evolution of the small-angle X-type strike-slip fault in Tabei uplift were analyzed. The study shows that the strike-slip fault in Tabei uplift has clear vertical delamination deformation characteristics, comprising three structural layers: (lower) Sinian-Middle Cambrian (below TH3 interface), (middle) Upper Cambrian-Middle Ordovician (TH3-TO3t interface), and (upper) Upper Ordovician-Carboniferous (TO3t-TP interface). The fault was generally in a transpressive setting in the lower and middle structural layers, and developed most of the positive flower structures. In contrast, negative flower structures and normal faults were mainly developed in the upper structural layer, which was in a transtensional setting as a whole. Comparing the two fault sets, the NNW-trending ones are highly active, and there are distinctive fault characteristics in each structural layer, together with strong vertical connectivity, and the development of pre-existing basement faults. Meanwhile, the NE-trending faults are mainly developed in the middle structural layer, but unclear in the lower and upper structural layers. Activity analysis shows that the formation and evolution of faults are multistage, and that the strike-slip faulting had undergone three major phases in the late Middle Cambrian, Middle-Late Ordovician and Silurian-Carboniferous. Formation of the X-type strike-slip faults in Tabei uplift was controlled by the NNW-trending basement faults and weak zones. Strike-slip faults are developed preferentially in NNW-trending basement faults or structural weakness zones, and the angle between the basement faults and the main compressive stress direction is less than 45 °-Φ/2. Development of NNE-trending faults was restricted by the pre-existing NNW-trending faults, and finally the X-type faults intersecting at small angles were formed.

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    Analysis of Soil Selenium Bioavailability and Its Influencing Factors Based on DGT Technology
    JIANG Tianyu, YU Tao, HOU Qingye, QI Hongbin, WANG Jue, MA Xudong, YANG Zhongfang
    Geoscience    2021, 35 (03): 637-646.   DOI: 10.19657/j.geoscience.1000-8527.2021.03.05
    Abstract538)   HTML7)    PDF(pc) (3029KB)(325)       Save

    Se is one of the important trace elements in the environment, and the accurate evaluation of its bioavailability has always been controversial. Sixty sets of crop and root soil samples were collected in Linshui County, Guang’an City, Sichuan Province, and the Se content, physical properties, and chemical properties of crops and soil were analyzed. Results showed that the total Se content in the soil of the study area ranged from 0.15 mg/kg to 2.42 mg/kg (average=0.48 mg/kg). The total Se content of the different types of soil in the study area was considerably different and followed the order: lime soil (1.06 mg/kg)>yellow soil (0.78 mg/kg)>purple soil (0.28 mg/kg)>paddy soil (0.27 mg/kg). The organic matter and the total Fe2O3 (TFe2O3) contents of the lime and the yellow soil samples were remarkably higher than those of the other types of soil. The content of the DGT-Se in the different types of soil in the study area was evidently different. The correlation analysis showed that the soil DGT-Se was significantly related to the total Se, TFe2O3, S, organic matter, and Al2O3 contents and pH of the soil (p<0.01). The influence of its physical and chemical properties led to differences in the DGT-Se in the different types of the soil. The content of the DGT-Se in the soil of rice roots was significantly positively correlated with the Se content in rice seeds (r=0.55, n=29, p<0.01). The DGT could be used as an indicator for the bioavailability of the soil Se in the rice-root soil system. The type, physical properties, and chemical properties of the soil should be fully considered in the evaluation and the prediction of the available Se content of agricultural soils on a regional scale on the basis of the DGT technology.

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    Geochemical Characteristics and Genesis Analysis of Daheba Epimetamorphic Graphite Deposit in Wangcang, Sichuan Province
    DUAN Wei, TANG Wenchun, LI Longchang, RAN Qiang, ZHANG Fei, LI Xiaosong, XU Yongsheng
    Geoscience    2021, 35 (03): 599-607.   DOI: 10.19657/j.geoscience.1000-8527.2021.03.02
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    Daheba graphite deposit is a newly discovered large phanerocrystalline graphite deposit in the southern margin of Micangshan, northern Sichuan. The geological characteristics of the deposit and the geochemical characteristics of major, trace elements and rare earth elements of minerals are studied in the paper. The results show that the ore bearing strata are parametamorphic rocks. The original rock deposition of graphite ore body in Daheba mining area is under anoxic reduction environment, and the protolith is composition of carbonaceous clayey fine to silt stone and carbonaceous marlite. The characteristics of trace elements indicate that the ore body is mainly composed of terrigenous clastic sediments. The sedimentary water is mainly fresh to brackish water with low salinity and uneven mixing. The average value of ∑REE of the ore is 150×10 -6, which is similar to marlite; The average value of δCe is 0.91, Ce indicating weak negative anomaly; The average value of δEu is 0.67, Eu is negative anomaly and has the characteristics of coastal tidal flat facies deposition; The δ 13C values of the ore bearing rocks ranged from -21.4‰ to -19.0‰, with an average of -19.86‰, indicating that the main source of metallogenic carbon is organic carbon, which may be mixed with some inorganic carbon. The genetic type of the deposit is sedimentary metamorphic. The metamorphism may be multiple regional metamorphism and superimposed migmatization.

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    Development of the Chinese Continental Scientific Deep Drilling: Perspectives and Suggestions
    ZOU Changchun, WANG Chengshan, PENG Cheng, WU Caowei, GAO Yuan
    Geoscience    2023, 37 (01): 1-14.   DOI: 10.19657/j.geoscience.1000-8527.2022.101
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    As the most direct and important method to detect the Earth’s deep interior, scientific drilling plays a key role in solving the strategic technological issue of deep Earth exploration. This study briefly reviews the development and current situation of domestic and international continental scientific drilling and deep drilling, and analyzes the characteristics and trends of continental scientific drilling development. We summarized the Chinese Continental Scientific Drilling, its key scientific and technological issues, as well as challenges and opportunities. Accordingly, we proposed the development goals, priorities and approaches of the Chinese Continental Scientific Drilling. Continental scientific deep drilling can provide a unique pathway for investigating global concerns in Earth sciences, such as geodynamic processes, geohazards, mineral and energy resources, and environmental changes. However, its implementation depth is constrained by ultra-high temperature and ultra-high pressure in harsh borehole environments. Modern scientific advances have promoted the development of various technologies in continental scientific drilling, which provide important support for ultra-deep and extra-deep drilling. The Chinese Continental Scientific Drilling should aim for 9,000-15,000 m extra-deep boreholes, focusing on scientific issues in the fields of ultra-deep, deep-time and deep-observation. Priority development directions can include deep Earth tectonics, deep-life, deep-climate, and deep-resources. The priority detection technologies can include those for drilling, logging, and long-term observation in ultra-high temperature-pressure environments. Priority should also be given to the experimental technique development for ultra-deep matter, dynamics processes, and petrophysics. This would promote a breakthrough in the capacity and level of Earth interior detection in China.

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    Geochemical Constraints on the Sedimentary Environment of Wenchang Formation in Pearl River Mouth Basin and Its Paleoenvironmental Implications
    GAO Yangdong, LIN Heming, WANG Xudong, QIU Xinwei, QUE Xiaoming, LI Min, ZHAO Zeying, CHEN Yan
    Geoscience    2022, 36 (01): 118-129.   DOI: 10.19657/j.geoscience.1000-8527.2021.198
    Abstract457)   HTML10)    PDF(pc) (4171KB)(303)       Save

    Terrestrial input is the main external nutrient source for the growth of oil parent matter (e.g.bacteria, algae, phytoplankton) in lacustrine environment. Paleoclimate conditions affect terrigenous input, and lacustrine sedimentary environment controls organic matter preservation. Understanding the paleo-lacustrine environment is critical to predict organic matter abundance in source rocks. Here, we present new geochemical data from source rocks of the Wenchang Formation in the Lufeng Sag of Pearl River Mouth Basin. Element geochemical indices, e.g.CIA, V/Cr, Mn/Al, Sr/Cu and Ti/Al, altogether reveal the climate,lake-level, paleo-oxygen and paleo-salinity conditions and show that the paleo-environment played an important role in controlling the source rocks. High level of chemical weathering corresponds to high organic matter in the lower part of E2w3 and E2w4. Lake-level and paleo-oxygen changes are responsible for the organic matter enrichment of E2w. Meanwhile, the paleo-salinity are less relevant. The organic-rich source rocks of the E2w4 and E2w3 (lower part) of the LF-A well in the Lufeng Sag were likely formed in a deep and reduced lake with strong chemical weathering, under the conditions of warm-humid climate, sufficient nutrient supply, and high productivity.

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    Geochronology and Petrogenesis of the Highly-Fractionated Early Cretaceous Narenwula Granite, Inner Mongolia, China
    LI Zhu, ZHANG Dehui, ZHANG Rongzhen, SHEN Cunli, JIAO Shihao, LI Lin, ZHU Penglong
    Geoscience    2022, 36 (03): 848-861.   DOI: 10.19657/j.geoscience.1000-8527.2021.064
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    A number of rare metal deposits have been discovered in Narenwula area of Inner Mongolia, with high metallogenic potential. However, there are still many controversies about the chronology and genesis of Narenwula granite. LA-ICP-MS zircon U-Pb dating and geochemical analysis have been carried out to determine the age and genetic type of the Narenwula granite. The U-Pb dating results show that the medium-coarse biotite monzogranite and porphyritic monzogranite were emplaced in the Early Cretaceous, at (142.1±1.0)Ma and(142.3±1.2)Ma, respectively. Its diagenetic age is basically consistent with the ages of the extensive regional granite emlacement in the Late Jurassic-Early Cretaceous period. Whole-rock geochemistry shows that the granite is characterized by high silica(SiO2=73.69%-76.67%)and alkali(Na2O+K2O=8.40%-8.80%), but low P2O5, MgO, FeOT, CaO, and REE. The rocks have high LREE/HREE ratios(LREE/HREE=6.23-14.28) and marked negative Eu anomalies (δEu=0.20-0.36). They are obviously enriched in Zr, Hf, Rb, and Th, but strongly depleted in Ba, Sr, P, and Ti, and slightly depleted in Nb. The granite is high-K calc-alkaline and weakly peraluminous. Based on the characteristics of mineralogy, petrology and geochemistry, we concluded that the granite belongs to highly-fractionated I-type. Considering the structural features and regional geological background, we inferred that the Narenwula granite in the northern margin of the North China Plate was formed in the Early Cretaceous within-plate extensional setting.

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    Characteristics and Development Pattern of Pre-Mesoproterozoic Carbonate Subduction Reservoirs in the Qiaogu Area of the Tabei Uplift
    LIU Qian, FAN Tailiang, GAO Zhiqian, ZHANG Tonghui, MA Xiaoxuan, WEI Duan, LU Xinbian
    Geoscience    2022, 36 (05): 1391-1402.   DOI: 10.19657/j.geoscience.1000-8527.2022.048
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    The buried hill formation of the pre-Mesozoic in Qiaogu area is the key area for the breakthrough of oil and gas exploration in Tabei Uplift, Xinjiang.The buried hill strata in this area are deep and complex in distribution, the reservoir is highly heterogeneous and strongly transformed by late fluid activity, and the law of oil and gas enrichment is unclear, which seriously restricts regional oil and gas exploration and target selection.In order to find out the characteristics of buried hill reservoir and the main controlling factors of reservoir development and establish the reservoir development model, the reservoir characteristics and controlling factors were systematically studied by using core, drilling and logging data and seismic data.The results show that the pre-Mesozoic reservoir lithology in Qiaogu area is mainly composed of three types: crystalline dolomite, siliceous dolomite and granular dolomite.The reservoir space is dominated by fractures, followed by dissolved pores, and locally developed karst caves.The physical properties of different lithofacies are obviously different. Fine silty dolomite, calcareous silty dolomite and sand-clastic micritic dolomite reservoirs are well developed, and the reservoir matrix has good physical properties.Micritic dolomite and siliceous dolomite are relatively compact and non-reservoir with poor physical properties.Based on the above research, the reservoir development model of the inner buried hill in Qiaogu area is extracted, that is, the reservoir development is mainly controlled by lithofacies, faults and burial-hydrothermal interaction, among which lithofacies is the material basis of reservoir development, faults are the key factors of reservoir development, and burial-hydrothermal transformation of reservoir development is superimposed.Compared with the reservoir unit characteristics of the target strata, there are five sets of small development strata in the upper member of the Xiaerbulak Formation, among which the first, third and fourth development strata have good reservoir physical properties and reservoir-cap combination, which are the preferred key targets for future oil and gas exploration and target areas.

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    Geoscience    2021, 35 (06): 1486-1486.  
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    Construction and Test of a Geochemical Lithogene Based on Trace Elements: Case Studies on Weathering Profiles in China
    LI Jie, LIU Ningqiang, GONG Qingjie, WU Xuan, YAN Taotao
    Geoscience    2021, 35 (05): 1459-1470.   DOI: 10.19657/j.geoscience.1000-8527.2021.039
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    Geochemical gene is a new technique presented in recent years. According to the construction steps of a geochemical gene, a new lithogene labelled LG03 was proposed based on trace elements on the sequence of Nb→Ti→Zr→Cr→La→V→Pb→Co→U→Ni→Th with the standardized reference values of 14.5, 4,016, 147, 81, 35, 130, 19, 24, 1.2, 32, and 5.72, respectively in μg/g. The LG03 lithogene along with the LG01 lithogene which was constructed formerly on major oxides and trace elements were tested on 10 weathering profiles including 4 profiles developed over granitic intrusions, 4 profiles formed on basaltic strata, and 2 profiles developed on granodioritic intrusions in Guangdong Province, Hainan Province, Shandong Province, and Beijing City in China. According to the gene similarity value of ≥80% as the criterion to discriminate samples with similar lithogenes, the gene similarity results on 10 weathering profiles indicate that LG03 and LG01 lithogenes all illustrate good steady during rock weathering on the properties of heredity (gene similarity with respect to parent rock) and inheritance (gene similarity with respect to topsoil). Furthermore, according to the acidic similarities (gene similarity with respect to the gene of 10202020202 on LG01 and LG03), samples can be classified into three groups as acidic-like composition with values of ≥80%, intermediate-like composition with values between 75% and 25%, and basic-like composition with values ≤20%. That is to say, LG03 and LG01 have similar effects on composition classification and provenance discrimination. However, LG03 is more stable than LG01 in the properties of heredity and inheritance and the application on provenance discrimination. When the results of compositional classification on LG03 and LG01 are different, the results on LG01 are recommended and the results on LG03 are also helpful for a further constraint. The concentrations of major oxides (such as SiO2, CaO, P2O5, etc.) in geological materials will be changed clearly resulted from the addition of aeolian sands, organisms, etc. during the weathering, transportation, sedimentation processes. Therefore, the LG01 lithogene which was constructed on both major oxides and trace elements may be unstable while the LG03 lithogene constructed only on relative immobile trace elements may illustrate good stability during the geological processes. Hence, the LG03 lithogene may have wider application fields than LG01 lithogene because of the elimination of addition or dilution effects in geological materials.

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    Characteristics of Stromatolites and Its Significance in Depositional Environment Reconstruction of the Mesoproterozoic Longjiayuan Formation (2nd Member), Western Henan
    LI Qianqian, ZHENG Deshun
    Geoscience    2023, 37 (04): 845-857.   DOI: 10.19657/j.geoscience.1000-8527.2022.023
    Abstract153)   HTML27)    PDF(pc) (12773KB)(281)       Save

    Stromatolites recorded the life activities of early environment, cyanobacteria and microbial community, and their growth morphology was influenced by the sedimentary environment, which is of great significance for the paleo-environmental reconstruction. Stromatolites from the Longjiayuan Formation (2nd member)of the Mesoproterozoic Guandaokou Group in western Henan have various morphological types and concentrated in distribution, which is a typical area for stromatolites development. The distribution of stromatolites is closely related to global events, geochemical environment of the Precambrian ocean and the development of microbiolites, yet detailed research is still lacking. Based on this, we conducted a systematic field investigation and petrological examination on the microbialite structure on these stromatolites, studied the macroscopic and microscopic characteristics of the stromatolites, established the sedimentary environment evolution and sedimentary model, and compared with the stromatolites from other areas. The results show that the macroscopic morphology of the stromatolites can be divided into horizontal laminae, ripple, hilly, cone, and column. Microscopically, the stromatolites are light and dark laminae, with few ooids, spherular and detrital materials locally. The shape and scale of stromatolites are closely related to the hydrodynamic conditions and water depth. Horizontal laminated stromatolites were developed in the intertidal zone, whilst corrugated and mound stromatolites were developed in the intertidal high-energy zone and low-energy zone. Meanwhile, cone and columnar stromatolites were developed in the subtidal zone. Our comprehensive analysis shows that our stromatolite samples were formed in a tidal-flat environment, and were influenced by the sedimentary evolution process of intertidal, subtidal and intertidal zones. It is beneficial to analyze the Early Mesoproterozoic development environment of microbiolites in the southern margin of North China. Besides, we compared our results with the sedimentary environment of microbiolites in Jixian area (northern margin of North China), in order to explore the relationship between marine environment, atmospheric environment, and microbiolites around the North China Craton.

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    Geochemistry, Zircon U-Pb Chronology and Lu-Hf Isotope Characteristics of Monzogranites from Aishan Pluton in Jiaodong Peninsula
    LI Xiuzhang, WANG Ligong, LI Yixin, WANG Yingpeng, YU Xiaowei, ZHANG Wen, GUO Ruipeng, LIU Handong
    Geoscience    2022, 36 (01): 333-346.   DOI: 10.19657/j.geoscience.1000-8527.2022.01.30
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    The large-scale gold mineralization in Jiaodong Peninsula occurred from 125 to 110 Ma. Early Cretaceous Aishan pluton, coincided with the gold mineralization, is distributed in the eastern margin of North China Craton. Aishan pluton is composed of deep-facies quartz diorite-porphyry monzonitic granite and shallow-facies diorite porphyry, granite porphyry, etc., and develops mafic enclaves. Based on the studies of the petrography, geochemistry, zircon LA-ICP-MS U-Pb dating and Lu-Hf isotopic constitution of Aishan monzogranites, this paper discusses the petrologic classification, forming age, magmatic source and petrogenesis. Zircon U-Pb age of Aishan pluton is( 115±1)Ma. Aishan pluton is characterized by Na2O>3.47, A/CNK<1.35, high Y content (8.2×10-6-210.5×10-6), low Sr/Y ratio (19.5-67.3), with obvious rare earth element fractionation (LREE/HREE=28.43-34.72, (La/Yb)N=46.38-56.74), and negative Eu anomaly (δEu=0.75-0.83). Aishan pluton is a set of quasi-aluminous-weak peraluminous high-potassium calc-alkaline rock series, showing the characteristics of I-type granite. Aishan monzogranites have zircon εHf(t) values of -19.7 to -16.0, and two-stage Hf model ages (TDM2) vary in range of 2.18-2.42 Ga. According to the petrology, geochemistry and Lu-Hf isotopic constitution, combined with the results of previous studies on the genesis of Weideshan granite, the authors hold that Aishan monzogranites are a production of mixture between crustal acid magma and mantle intermediate-basic magma. The magma mainly derived from ancient Proterozoic and Neoarchean continental crust material.

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    HEC-RAS-/GIS-Based Paleohydraulic Reconstruction of the Diexi Ancient Landslide-Dammed Lake Outburst Flood in Western Sichuan Province
    MA Junxue, CHEN Jian, CUI Zhijiu, LIU Beibei
    Geoscience    2022, 36 (02): 610-623.   DOI: 10.19657/j.geoscience.1000-8527.2021.168
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    Landslide-dammed lakes and outburst floods have been widely developed along the Upper Minjiang River valley, due to the complex geological environmental conditions in this region. Hazard evolution reconstruction has major significance for regional disaster prevention and mitigation. This study is dedicated to the Diexi ancient landslide-dammed lake (DALL) triggered by a strong paleoseismic in the Upper Minjiang River in Western Sichuan Province, at the southeastern margin of the Tibetan Plateau. We focus on the fluid dynamics of downstream megaflood characteristics. The estimated former lake size was 1.1×107 m2, and the impounded volume was 2.9×109 m3. The maximum peak discharge and paleohydraulics of the landslide-dammed lake outburst flood (LLOF) were reconstructed with empirical equations and one-dimensional (1D) HEC-RAS hydraulic numerical model. The results reveal that the maximum peak flow of the Diexi ancient LLOF by HEC-RAS was 73,060 m3/s, largely similar to the results by the empirical methods (74,500-76,800 m3/s, avg. 76,000 m3/s), with an error of < 5%. The corresponding maximum flood depth and flow velocity are 70.1 m and 16.78 m/s, respectively. The inundated area during the modeled reach of Minjiang River was approximately 6.08 km2. The uncertainty bound of the maximum peak discharge was determined to be 69,000-81,000 m3/s. The maximum peak discharge of the Diexi ancient LLOF was more than one hundred times the average annual flow of Minjiang River (approximately 700 m3/s), indicating that it was an abnormally large outburst flood in Diexi Region once in a hundreds-of-thousand years in history, and also one of the world’s largest LLOFs. The direct consequence of the high-energy outburst flood was the formation of band- or terrace-shaped outburst deposit bars and boulder deposit terraces on both sides of the gorge and river-bed in the downstream. These findings are consistent with previous hydrological and sedimentary studies on the high-energy outburst floods, demonstrating the high reliability of our results. In addition, this study also shows that the 1D HEC-RAS model can be used to reconstruct the hydraulics of an ancient LLOF in deep-confined gorge environments. This study is of great significance to the paleoenvironment reconstruction and geomorphic evolution in the upper reaches of Minjiang River.

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    Distribution Coefficient of Ra in Groundwater and Its Determination Technique
    HAO Xin, YI Lixin, LI Luxuan, YANG Yongpeng
    Geoscience    2022, 36 (02): 552-562.   DOI: 10.19657/j.geoscience.1000-8527.2022.007
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    In the past decade, the Ra isotope has attracted increasingly more research attention in the field of water environment and water resources. Important findings have been made on the application of Ra isotopes in estimating seabed groundwater discharge, calculating lake water balance, study of groundwater age and analysis of groundwater pollution source. This is due to the development of Ra isotope analytical technology and the enhanced understanding of Ra geochemical behavior. The Ra distribution coefficient (Kd) is a key parameter affecting the Ra migration in soil and aquifer, and its understanding is pivotal for accurate tracing of hydrological processes, especially groundwater cycle. We compiled a range of Kd value and analyzed the main influencing factors. We found that the Kd value in natural environment varies from 0.1-1×106 mL·g-1, extending across seven orders of magnitude between the maximum and minimum. The water salinity, pH, and Fe content in sediments have significant impact on Kd. The Kd determination methods were summarized and divided into four types, including the (1) “Rn” equilibrium, (2) thermodynamic adsorption equilibrium calculation, (3) experimental method, and (4) ion exchange equilibrium method. The pros and cons of each method were analyzed. We proposed the establishment of an accurate determination method of ion input recoil term in aqueous solution and to optimize analysis and calculation process, which is the technical idea of obtaining Kd value accurately. Our review and analysis can provide reference and technical support for studying the hydrogeochemical properties of Ra and its hydrologic applications.

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    Geothermal Geological Characteristics of the Xianxian High and Fucheng Sag in the Middle Cangxian Uplift, Bohai Bay Basin
    HUANG Xu, SHEN Chuanbo, DU Li, WEI Guangren, LUO Lu, TANG Guo
    Geoscience    2021, 35 (04): 997-1008.   DOI: 10.19657/j.geoscience.1000-8527.2021.043
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    To explore the karstic reservoir distribution in the North China Platform, and enhance the geothermal energy utilization in the Xianxian high and Fucheng sag geothermal field, we analyzed the distribution of karst reservoir of Xianxian high and the Fucheng sag and the four major influencing factors (i.e.source, reservoir, migration channel, and cover) geothermal fields. Based on logging, seismic, and hydro-chemical data, a conceptual model for the geothermal field is established, and the geothermal resource evaluated. It is considered that the geothermal field is a conductive one, which was formed in a continental extension basin and controlled by deep faults. It formed a medium-low temperature conductive geothermal system, which is characterized by good caprock and geothermal gradient (3.63 to 5.31 ℃/100 m), whose recharged water source comes from atmospheric precipitation in the Taihangshan and Yanshan, and concentrated in karst heat reservoir of the Xianxian high and Fucheng sag. Specifically, the burial depth of the Jixian karst thermal reservoir is 1,400 to 1,500 m (effective thickness 336.1 m) in the Xianxian high geothermal field, whilst the Ordovician karstic reservoir is 2,000 to 2,500 m (effective thickness 55.3 m) in the Fucheng sag geothermal field. The total extractable geothermal resource of Jixian karstic reservoir in the Xianxian high geothermal field is 3.75×109 GJ, (1.28×108 t standard coal eqv.), and the annual geothermal resource can meet the indoor heating demand of 45.23 million. The total extractable geothermal resource of the Ordovician karstic reservoir in the Fucheng sag geothermal field is 0.80×109 GJ, (0.27×108 t standard coal eqv.), and the annual geothermal resource can meet the indoor heating demand of 9.54 million. The geothermal field development potential is likely immense.

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    Zircon U-Pb Geochronology, Geochemical Characteristics and Geological Significance of Huangyugou Intrusion, Shanxi Province
    YE Feng, DONG Guochen, REN Jianxun, GONG Jieli, LI Mengxing, WANG Quan, ZHANG Zhaoqi, ZHAO Sanbo
    Geoscience    2021, 35 (03): 787-797.   DOI: 10.19657/j.geoscience.1000-8527.2020.055
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    To deepen our understanding on the destruction mechanism in the North China Craton, we report new geochronological and geochemical data on the fresh quartz monzonite porphyry from the Huangyugou intrusion in Shanxi. The Huangyugou intrusion is composed of quartz monzonite porphyry, which yielded a Late Jurassic weighted mean 206Pb/238U age of (149.3±0.9) Ma. The quartz monzonite porphyry samples are metaluminous and shoshonitic, enriched in large ion lithophile elements (LILEs, such as K, Sr and Eu), and depleted in high field strength elements (HFSEs, such as Nb, Ce, Zr and Ti). The rocks exhibit LREE/HREE enrichments and weak Eu anomalies. The quartz monzonite porphyry is classified as I-type and shows adakitic features, including high Al2O3, Sr, Ba, and Sr/Y, but low Y and MgO. Geochemical characteristics indicate that the Huangyugou intrusion was formed from partial melting of the lower crust, with mantle-derived inputs and have undergone magma mixing. The rocks may have formed under an extensional tectonic setting.

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    Experimental Study on Mechanism of Heavy Rainfall-induced Loess-mudstone Landslides in Tianshui Area,Gansu
    HAN Shuai, SUN Ping, LI Rongjian, ZHANG Jin, LI Xiaobin, ZHU Enzhen
    Geoscience    2021, 35 (03): 720-731.   DOI: 10.19657/j.geoscience.1000-8527.2020.024
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    Rainfall-induced loess-mudstone landslide disasters are common every year in the Tianshui area (Gansu Province), causing significant loss of life and property. Based on field geological survey, engineering geological drilling, and rock and soil mechanics analyses, and through laboratory large-scale physical modelling experiment, we explore the dynamic deformation process of heavy rainfall-induced landslides (which are characterized by loess-mudstone bimodal structure), and reveal the failure mode and mechanism for this type of landslide. The results show that the slope deformation is mainly manifested as sliding damage under heavy rainfall. The role of water is mainly on increasing the soil weight and pore water pressure, and decreasing the soil strength, effective stress, and sliding resistance of the structural surface. Meanwhile, the failure mode of landslide is mainly manifested by slope shoulder erosion→microcrack growth and interconnection→local failure→overall sliding failure. Our findings are important for early-stage landslide recognition and provide scientific basis for landslide-related disaster prevention in the region.

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    Sinistral Ductile Shear and Magmatic Migration Pattern in the Late Mesozoic Yishu Fault Zone
    LI Sheng, NI Jinlong, ZHANG Shangkun, SHEN Ying
    Geoscience    2021, 35 (03): 776-786.   DOI: 10.19657/j.geoscience.1000-8527.2021.060
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    Magma intrusion in the Yishu fault zone (YFZ) is closely related to fault activity, and the magmatic geochronology in the Yishu fault zone is of major significance for revealing the tectonic setting of the YFZ. Petrological and LA-ICP MS zircon U-Pb geochronological analyses were conducted on the Fulaishan syenite (in Juxian) in the Yishu fault zone, as well as the Guanfang quartz syenite (in Junan) and the intruding diorite porphyrite dykes. The sinistral ductile shearing of the Late Mesozoic YFZ was first recognized. Zircon U-Pb dating yielded (125.1±1.7) Ma (Fulaishan pluton), (125.6±2.0) Ma (Guanfang pluton), and (122.8±2.1) Ma (ductile-deformed diorite porphyrite dyke). The 125 Ma magmatic age obtained is consistent with the rapid exhumation (122-128 Ma) of the Wulian metamorphic core complex (MCC) and the rapid sedimentation in the Zhucheng fault-bounded basin on the eastern side of the YFZ. This indicates that the YFZ was in a period of intense lithospheric thinning and destruction. The 122.8 Ma age of the diorite porphyrite dike is consistent with the crystallization age of the post-Wulian MCC (e.g., Shichang and Fangzi plutons), indicating that the extension of the YFZ was significantly weakened during this period. It also shows the similar timing of lithospheric thinning across the Jiaodong Peninsula. During the Late Mesozoic, magmatism on both sides of the YFZ had a counterclockwise migration pattern, which may have related to the changing direction, angle, and/or velocity of the Izanagi plate subduction beneath the Eurasian plate.

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    Advances on the Understanding in the Emeishan Mantle Plume and Dynamic Mechanism of the Permian Sichuan Basin Formation
    SUN Ziming, BIAN Changrong, LIU Guangxiang
    Geoscience    2023, 37 (05): 1089-1099.   DOI: 10.19657/j.geoscience.1000-8527.2023.043
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    In recent years, significant research progress has been made on the Emeishan Large Igneous Province (ELIP) and its genetic mechanism of mantle plume, but the scope of the mantle plume on the Sichuan Basin and the dynamic mechanism for the Permian sedimentary basin formation remain unclear.Based on a number of literature research and recent studies, and the idea that deep mantle activity controls the evolution of crustal surface system, the characteristics of Emeishan LIP and its deep geology are systematically reviewed.It is recognized that the mantle plume is the dominant factor that induces the large-scale eruption of the Emeishan basalts and formed the LIP, and has direct influence on some parts of the Sichuan Basin, which is manifested by the differential denudation of the top Middle Permian Maokou Formation.This was likely caused by the upwelling of mantle plume and its control on the Permian sedimentation and sedimentary facies distribution in the central-southern part of the basin.Formation of the extensional troughs, and the alternating high-and-low sedimentary-tectonic framework in the central-northern Sichuan Basin during the Permian to Early Triassic may have been mainly controlled by the extension of the southern Qinling Ocean.

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    Tectonic Evolution of Songnan-Baodao Sag in Qiongdongnan Basin and Its Relationship with Oil-gas Reservoir
    WANG Kai, WANG Genhou, JIA Qingjun, ZHANG Xiao
    Geoscience    2023, 37 (02): 245-258.   DOI: 10.19657/j.geoscience.1000-8527.2022.057
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    The Songnan-Baodao depression is an important exploration area with great oil-gas exploration and development potential in the Qiongdongnan Basin (after the Yacheng-Lingshui Depression), and its tectonic evolution, tectonic style and prototype basin restoration are of great significance to understand the oil and gas accumulation regularities. Based on seismic data interpretation, we used 2DMove software to analyze the tectonic evolution period and the spread regularities of tectonic patterns of the Songnan-Baodao depression, and restored the characteristics of Paleogene prototype basins. The results show that the tectonic-sedimentary evolution of the Songnan-Baodao depression can be divided into six stages in three periods (pre-rift, syn-rift and post-rift), and the structural styles comprise three major categories and 14 sub-categories of simultaneous deformation styles, and simultaneous style and multistage style assemblages. Eight dustpan-like fault deposits were recovered in the local Paleogene prototype basins, with sediment thickness of 3,000-6,000 m. Preservation status of the three types of Paleogene prototype basins in the strong, medium and weak transformation areas were identified, and the local erosion thickness exceeds 5,000 m. The oil and gas transport characteristics of the Songnan-Baodao depression are characterized by source proximal, high maturity and late accumulation, and the Songtao bulge, Lingshui low bulge and Songnan bulge at the periphery represent both the oil-gas transport directional zones and effective traps of buried-hill and nappe structure, stratigraphic lithology, and inverted anticline. accumulation match the large-scale hydrocarbon generation period, which are favorable for oil and gas exploration.

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    A Novelty Method of REE Parameter Diagrams: A Case Study of Petrogenesis of Bairendaba-Weilasituo Dioritoids in Inner Mongolia
    ZHAO Baoju, YAN Kai, XIAO Rongge
    Geoscience    2021, 35 (03): 608-624.   DOI: 10.19657/j.geoscience.1000-8527.2021.03.03
    Abstract420)   HTML13)    PDF(pc) (4487KB)(254)       Save

    REE parameter diagrams are important tracers for geochemical and geological studies which show potential for the rapid determination of petrogenesis and magma source. By using REE and SiO2, LREE and LREE/HREE, δEu and LREE/HREE diagrams of dioritoids, we investigate the correlation among REE parameters taking the Bairendaba-Weilasituo dioritoids as an example. Through field petrological observation and whole-rock geochemical data, new REE parameter diagrams and REE R-type cluster analysis, this paper studied the petrogenesis and magma source. The results show that the Bairendaba-Weilasituo dioritoids have high SiO2, Na2O, MgO, and Al2O3 contents, and belong to the calc-alkaline series, indicating the mixing source of magma from both the mantle and the lower crust. The high-REE values of the Bairendaba-Weilasituo dioritoids respectively show negative correlation and positive correlation between LREE/HREE-REE and δEu-LREE/HREE, and show obviously negative Eu anomaly. They are enriched in Rb, Th, U, and K, and depleted in Nb, Ta, Sr, P, and Ti, whereas the low-REE values show absolutely contrary characteristics. We concluded that this suite of calc-alkaline dioritoids were originated from the mantle substance dominated by hybrid crust-mantle mixing magma associated with an active continental margin. The developed method can be used for estimating petrogenesis and magma source in Bairendaba-Weilasituo calc-alkaline dioritoids refe-rence materials. This empirical method shows great potential for the rapid determination of petrogenesis and magma source in large batches of samples commonly analyzed for mineral exploration and REE geochemistry studies.

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    Deformation Characteristics and Evolution of the Eastern Xiangfan-Guangji Fault Zone
    ZHU Qingbo, CHENG Wanqiang, ZHOU Quan
    Geoscience    2022, 36 (03): 755-769.   DOI: 10.19657/j.geoscience.1000-8527.2021.142
    Abstract581)   HTML124)    PDF(pc) (12716KB)(254)       Save

    The Xiangfan-Guangji fault zone(XGF) is a boundary fault separating the Dabie orogen and the foreland fold-thrust belt on the northern Yangtze cratonic margin. Its geometry, kinematics and structural evolution characteristics have recorded the collision, assembly and interaction between two tectonic units in the north and south. Based on field investigation, structural and geochronological analyses, and combined with published regional geological and geophysical data, we considered that the eastern XGF is characterized by a “crocodile mouth” offset structure of deep south-directed thrust and shallow north-directed thrust, which differs significantly from the structural deformation style and sequence of the western XGF. The eastern part of the middle Yang-tze block is controlled by the N-S-directed tectonic system. Subduction of the northern Yangtze cratonic margin beneath Dabie oregen may have extruded the orogen from north to south. The nappe structure may have affected the Ruichang area, and the shallow thrust nappe from south to north may have affected the vicinity of Meichuan. The two structures are likely connected in the Qichun-Wuxue-Xishui area in the eastern XGF. The XGF has undergone various structural deformation stages, including the N-S-directed thrust nappe ductile shearing (end T2), Early-Middle Yanshanian shallow bipolar offset detachment (J1-3), Late Yanshanian normal faulting (K1-2), and minor early Xishanian thrusting (E1) from north to south.

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    Fluvial Geomorphology of the Eastern Altyn Tagh and Its Tectonic Activity Implications
    LU Fang, GAO Mingxing, ZHOU Shuxian, WANG Shun
    Geoscience    2023, 37 (05): 1100-1109.   DOI: 10.19657/j.geoscience.1000-8527.2023.020
    Abstract103)   HTML11)    PDF(pc) (8829KB)(250)       Save

    The Altyn Tagh strike-slip fault zone is the major control fault at the northern margin of the Qinghai-Tibet Plateau, and plays a vital role in the Cenozoic crustal deformation of the plateau.We extracted and calculated five geomorphic indices (slope, relief amplitude, fractal dimension, hypsometric integral, and stream length gradient) of 173 sub-basins by ArcGIS software.The geomorphic indices of each sub-basin were classified into five types.Their arithmetic mean values were used as relative tectonic activity indices, in order to quantitatively analyze the topographical features and the tectonic activity intensity.We show that Altyn Tagh strike-slip fault zone is the dividing line for the relative tectonic activity intensity of the whole study area, and the relative tectonic activity index level gradually decreases from south to north, and from high to low mountai-nous areas.From the spatial distribution of the relative activity tectonic index grade, the tectonic activity in the Danghe and Yemahe River basins appears to be stronger, and the intensity gradually decreases from west to east.In addition, we combine the influence of rocks, precipitation, and tectonics on the geomorphic index.Our results show that tectonics is the main factor controlling the geomorphic development in the watershed of the Altyn Tagh strike-slip fault zone, the relative tectonic activity intensity in the watershed where the seismic point is located, the watershed on both sides of the fracture zone, and the stress transition zone are higher than those in other surrounding watersheds.

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    Magnetostratigraphy of Borehole ZK1 in Lingdingyang Bay, Pearl River Estuary
    CAO Kaijun, REN Jinke, LI Xiaomeng, WU Huaichun, CHEN Fang, YU Shaohua, SHI Meinan, GAN Huayang
    Geoscience    2022, 36 (01): 58-67.   DOI: 10.19657/j.geoscience.1000-8527.2021.165
    Abstract392)   HTML10)    PDF(pc) (8004KB)(247)       Save

    The establishment of the chronological framework in Lingdingyang Bay (Pearl River Estuary) is of great significance to regional paleoenvironment reconstruction and the study of sea-land interaction. Using magnetic stratigraphy and AMS 14C dating, the geochronology of 0-32 m cores in borehole ZK1 (113°40'E, 22°34'N, 100.3 m depth) in Lingdingyang Bay was analyzed systematically. The AMS 14C ages of the five samples range from (486±120) to (2,268±149) a BP. Rock magnetic analysis of the cores show that the magnetic minerals are mainly single-and multi-domain magnetite. Magnetic stratigraphy demonstrates core inversion in the coring process, and the magnetic sequence of the inverted core depth section is corrected. By comparing the core geomagnetic inclination and intensity with the standard curves and auroral records in East Asia, a high-re-solution stratigraphic age framework of borehole ZK1 (0-32 m) is established, with a bottom boundary age of 3.5 ka BP. Under this chronology framework, the core magnetic parameters have periodic changes of 3-8 a, 11 a and 21-25 a, which may have been related to the El Nino-Southern Oscillation, Pacific decadal oscillation, global surface temperature anomaly cycles, and solar activity.

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    Grain Size Characteristics and Its Response to Sediment Transport Trend in Changhua River Estuary, Hainan Island
    WANG Xuemu, QU Hongbao, XIONG Yuankai, LÜ Lin, HU Ke
    Geoscience    2022, 36 (01): 88-95.   DOI: 10.19657/j.geoscience.1000-8527.2021.172
    Abstract425)   HTML9)    PDF(pc) (6035KB)(244)       Save

    Grain size analysis and parameter calculations have been carried out for 110 surface sediment samples from the Changhua River Estuary, Hainan Island. Based on the Folk sediment classification ternary plot, the surface sediment samples can be divided into 10 sediment types: gravelly sand, sand, gravelly argillaceous sand, sandy gravel, silt-sand, mud, sandy mud, gravelly sand, sandy silt, and silty sand. Distribution range of sediment sand and gravel components is similar, and the particle size composition comprises mainly sand, silt-sand, and mud. Factor and cluster analysis of grain size parameters is used to discriminate different depositional environments. The study area can be further divided into the southern nearshore and northern offshore subareas. Grain size trend analysis suggests that the sediment transport pattern is consistent with the local hydrodynamic conditions. There are two aggregate sedimentation centers in the southern and northern parts of the study area. The material source of the banded sediments at Sigengsha Cape has also been identified.

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    Deformation and Activity Characteristics of the No.11 Strike-slip Fault Zone in the Shunbei Area, Tarim Basin
    KUANG Anpeng, YU Yixin, ZHU Xiuxiang, CHEN Shi, JIN Feng, LIANG Xinxin, YU Lang
    Geoscience    2021, 35 (06): 1809-1817.   DOI: 10.19657/j.geoscience.1000-8527.2021.199
    Abstract404)   HTML7)    PDF(pc) (10470KB)(244)       Save

    Strike-slip faults are widely developed in the Shunbei area, Tarim Basin, which play an important role in the hydrocarbon migration and accumulation. In this study, based on 3D seismic data interpretations of the western Shunbei area, the profile and plane geometry features, fault activity, active periods, and formation mechanism of the Shunbei-11 fault are characterized and analyzed. The Shunbei-11 fault extends to NNW for over 100 km, and is characterized by vertical/horizontal segmentation: The northern part is dominated by coeval transpression and transtension; two secondary faults formed a pull-apart graben in the middle part; a horsetail splay consists of several terminated branching faults in the southern part. The fault activities differ in deep and shallow layers, and decrease generally from south to north. The surface fault zone propagates from north to south, and the kinematic signatures suggest that it is a dextral strike-slip fault. Shunbei-11 fault underwent multiple active stages, and most of the fault has experienced two stages in the Late Ordovician (pre-T70) and Late Silurian-Middle Devonian (pre-T60), while some parts were active till Carboniferous. In terms of activity and kinematic features, the fault is similar to the NNW-trending strike-slip system of the Tabei uplift, but different from the NE-trending sinistral strike-slip system in the Tazhong uplift. Under the principal compressive stress (from north to south), and originated from the multistage collision of the South Tianshan Ocean north of the basin, the fault propagated from north to south, and the way of development and propagation was similar to that of the northern part of the Shunbei-5 fault.

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    Geoscience    2022, 36 (03): 754-754.  
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    Study on Organic Petrology Characteristics of the Wufeng-Longmaxi Formation Black Shale, Sichuan Basin
    LIU Siyi, GAO Ping, XIAO Xianming, LIU Ruobing, QIN Jing, YUAN Tao, WANG Xu
    Geoscience    2022, 36 (05): 1281-1291.   DOI: 10.19657/j.geoscience.1000-8527.2022.046
    Abstract372)   HTML8)    PDF(pc) (7415KB)(239)       Save

    At present, there is no unified classification and definition of organic macerals in the Wufeng-Longmaxi Formation black shale, which made it difficult for regional shale gas exploration and evaluation. In this study, organic macerals in the Wufeng-Longmaxi Formation black shale from the Sichuan Basin were identified and summarized via optical microscopic observation of polished blocks and organic geochemistry (TOC, δ13Corg), and their origins and organic matter types were determined. Our results show that organic macerals are mainly composed of the marine vitrinite, sapropelinite, organic zooclast and secondary groups. Among them, marine vitrinite group consists of round-/rod-shaped structureless vitrinite, and displays strong light reflection, but it is only locally distributed. The sapropelinite group is mainly composed of structureless sapropelinite, and is widely developed in organic-rich shale, which is the product of algal materials that underwent geological processes of thermal degradation. The organic zooclast group includes graptolite epidermis, chitinozoans and radiolarians. Meanwhile, the secondary group is composed of secondary bituminites, which is widely developed in matrix porosity of shales and is amorphous. The sapropelinite and secondary groups are the major types of organic macerals in the shales of Wufeng-Longmaxi Formation, whereas organic zooclast and marine vitrinite groups are less common. The organic matter type of studied shales is predominately type Ⅰ-Ⅱ1 kerogen. Moreover, the relative contents of sapropelinite and secondary groups increase, and organic matter type tends to oil-prone, contributing to their greater potentials of hydrocarbon generation.

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