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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
    Abstract1884)   HTML89)    PDF(pc) (15989KB)(877)       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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    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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    REE Characteristics in Surface Sediments of Zhanjiang Bay and their Provenance Indicating Significance
    YUAN Jidong, JIANG Zhenglong, DAI Youxu, HAO Liancheng, ZHANG Jiankang, ZHANG Decheng, ZHENG Lilong
    Geoscience    2022, 36 (01): 77-87.   DOI: 10.19657/j.geoscience.1000-8527.2021.166
    Abstract1114)   HTML19)    PDF(pc) (6817KB)(133)       Save

    Sediment geochemical characteristics and provenance in offshore Zhanjiang Bay were systematically studied by analyzing the grain size and rare earth elements (REEs) of surface sediment samples. The results show that the REE contents of sediments vary greatly (average 163.23 μg/g). The REE contents of outside the bay (168.61 μg/g) is higher than those in the bay (142.17 μg/g). The REE contents in different sediment types vary, which increase with the decrease of grain size. (La/Yb)N ranges from 4.80 to 11.76 (average 8.01); Europium anomaly (δEu) value ranges from 0.22 to 0.61 (average 0.45); Cerium anomaly (δCe) value ranges from 0.98 to 1.07 (average 1.03). The samples are characterized by typical light rare earth element (LREE) enrichment, homogeneity of heavy rare earth element (HREE) and distinct negative Eu anomaly, indicating that these sediments are terrigenous. Chondrite-normalized REE curves and REE parameters show that the sediments in Zhanjiang Bay are approximately homologous with those from around Jianjiang, Moyangjiang and Pearl Rivers, and are mainly sourced from granitoids in South China, basalts in northern Leizhou Peninsula, and unconsolidated sediments of the Zhanjiang and Beihai Formations.

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    Double-cross-shaped Distribution and Ore-controlling Characteristics of Structural Traces in Chaihulanzi Gold Deposit and Its Surrounding Area at Chifeng, Northern China
    ZHANG Baolin, LÜ Guxian, YU Jianguo, ZHANG Qipeng, SHI Xiaoming, WEI Junbin, WANG Cuizhi, BI Minfeng, ZHANG Tengfei, JIAO Jiangang, LEI Wuchao, SU Yanping
    Geoscience    2021, 35 (05): 1267-1273.   DOI: 10.19657/j.geoscience.1000-8527.2021.109
    Abstract1096)   HTML14)    PDF(pc) (7184KB)(154)       Save

    The Chaihulanzi gold deposit is located at the intersection of NNE-trending tectonic belt in the Great Hinggan Range and the EW-trending tectonic belt in the northern margin of North China Block. The Chaihulanzi, Lianhuashan, and Honghuagou gold deposits in the area have undergone multistage tectono-magmatic activity. Results of aeromagnetic and remote sensing data interpretation show four tectonic trending features (NNW, NWW, NNE and NEE) in the orefield, which constitute the double-cross-shaped structural pattern that controlled the emplacement of Late Paleozoic magmatic rocks (dikes) and gold mineralization. At Chaihulanzi, structural features of these four directions also form a double-cross-shaped pattern, which controlled the distribution of orebodies (mineralized zones) and geochemical anomaly zones. Both the orefield and ore-deposit tectonic features show the double-cross-shaped distribution characteristics, which demonstrate the magmatic and mineralization controled by different levels of the Neo-cathaysian tectonic system. Our findings provide an important foundation for studying metallogenesis and mineral prediction in the orefields.

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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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    Genesis and Geological Significance of Late Archean Syeno-monzogranite in Western Shandong Province
    YANG Fan, CHEN Yuelong, YU Yang
    Geoscience    2022, 36 (04): 1155-1172.   DOI: 10.19657/j.geoscience.1000-8527.2022.04.18
    Abstract864)   HTML14)    PDF(pc) (10063KB)(145)       Save

    The Western Shandong is located in the east of North China Craton, which is an important area to study the Archean evolution.Petrology, geochemistry and zircon U-Pb dating and Hf isotopic composition were studied on the syeno-monzogranite in the southwest of Western Shandong Province.The syeno-monzogranite is characterized by calc-alkaline and peraluminous affinities.Zircon U-Pb dating shows that the syeno-monzogra-nite emplaced at~2 540 Ma to~2 530 Ma.Zircon Hf isotopic compositions show that they were primarily molten by TTG rocks of~2.70 Ga, and there is recycled ancient crustal component. The mixing calculation results under constraints of isotopic and trace element compositions confirm that the primary magma of syeno-monzogranite is composed of the mixing of 97% of the juvenile TTG crustal material after partial melting and 3% of metamorphic supracrustal rocks after partial melting.Combined with previous studies, we propose that the syeno-monzogranite was formed in an extensional tectonic environment.The late Neoarchean magmatism in Western Shandong was related to slab rollback.The upwelling of asthenosphere caused by the rollback provided heat source for the formation of this group of rocks.

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    Climatic Changes and Impacts on Water Quality of Erhai Lake in Dali Area, Yunnan Province over the Period from 1989 to 2019
    AN Guoying, GUO Zhaocheng, YE Pei
    Geoscience    2022, 36 (02): 406-417.   DOI: 10.19657/j.geoscience.1000-8527
    Abstract819)   HTML24)    PDF(pc) (3826KB)(191)       Save

    In this study, we characterized the climatic changes and their impacts on lake eutrophication in Erhai Lake and assessed the relationships between air temperature, precipitation amount, and trophic status index of the lake using the climate data collected from 12 monitoring stations in Dali of Yunnan Province, and water quality monitoring data of Erhai Lake from 1989 to 2019. During this time, the annual mean air temperatures showed a fluctuating upward pattern which clearly indicated a warming trend with the largest temperature increases in the wintertime; meanwhile, the annual precipitation amount showed a fluctuating downward tendency with the most substantial declines in autumns. Comprehensive trophic status index, total nitrogen, total phosphorus, and permanganate index levels increased, while levels of water transparency declined. The changes in overall water quality were characterized by two distinct stages: before 2003, the comprehensive trophic status index, total nitrogen, total phosphorus, and permanganate index levels increased rapidly, while water transparency measured by Secchi Depth declined; after 2003, these same indices were relatively stable with minor fluctuations. We found that the comprehensive trophic status index of Erhai Lake was positively correlated with the annual mean air temperatures, but negatively correlated with the annual precipitation amount. Total nitrogen and water transparency levels showed a distinct correlation with both the annual mean air temperatures and precipitation. Total phosphorus was correlated clearly with the average winter air temperature, and the permanganate index levels correlated with the mean summer/winter air temperatures, respectively. In terms of monthly changes, both the water pollution index and comprehensive trophic status index increased substantially between June and October from 2015 to 2019, indicating water quality during the dry season was significantly better than during flood season. In summary, the comprehensive trophic status index of Erhai Lake increased continuously due to rising air temperatures, and reduced precipitation and lake inflow from 1989 to 2019, and the intensification of lake eutrophication has not improved and the water environmental condition of Erhai Lake remains relatively fragile.

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    Characteristics of Double-cross Structure in Neo-Cathaysian Structural System in the Middle-Lower Yangtze River Valley Region
    LÜ Guxian, ZHANG Baolin, LÜ Chengxun, HU Baoqun, ZENG Yong, GUO Tao, SHEN Yuke, WANG Hongcai, MA Licheng, JIAO Jiangang, BI Minfeng
    Geoscience    2021, 35 (05): 1240-1250.   DOI: 10.19657/j.geoscience.1000-8527.2020.065
    Abstract811)   HTML12)    PDF(pc) (3932KB)(143)       Save

    The tectonic system is composed of strongly-deformed structural belts and weakly-deformed region. These structural belts and blocks can be expressed in the form of structural planes. Structural plane analysis of the structural system is suitable for the study on the deformation rules, and it facilitates the tracing of structural stress field and evolution. Based on the study of the geological structures and the ore-forming/-controlling elements in the Middle-Lower Yangtze River Valley region, we summarized the distribution features of double-cross planes of the Neo-Cathaysian structural system. The double-cross structures of the Neo-Cathaysian structural system is composed of NNE-trending (25°) compressional fracture and fold belt, NNW-trending (345°, Dayishan-type) tension-torsional fractures, NEE-trending (75°, Taishan-type) compression-torsional structures, and NWW-trending (300°, Yangtze River-type) transverse extension structures. It contains three evolution stages: (1) the NNW 345° to NEE 75°-trending conjugate shear stage, (2) the NNE 25°-trending extrusion stage, and (3) the WWN 300°-trending tensile shear stage. Identification of the double-cross structural style of the Neo-Cathaysian structural system provides an important geological structural basis for the stress-strain genesis study, for the structural system formation and evolution, and for correlating shallow and deep structures. In addition, the structural planes have double-cross distribution features in other types of structural systems.

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    Fractal Characteristics Comparison and Genesis of Conventional Sandstone and Glutenite
    YANG Yi, ZHANG Hengrong, YUAN Wei, YANG Dong, HU Desheng
    Geoscience    2022, 36 (01): 149-158.   DOI: 10.19657/j.geoscience.1000-8527.2021.189
    Abstract796)   HTML5)    PDF(pc) (11514KB)(80)       Save

    Based on data from cast thin section, microscope, mercury-injection and conventional physical property analyses, we investigated the fractal characteristics of pore structure of glutenite reservoir developed in the Eocene Liushagang Formation of the Wushi Sag. The study includes the characteristics of fractal curves, fractal dimension and its relationship with reservoir physical properties and pore structure parameters, the effectiveness of fractal dimension in characterizing the storage and the permeability of different types of sandstones. The results show that compared with conventional sandstone, the high-pressure mercury fractal curve of glutenite presents has segmented features, indicating the development of three sets of pore-throat systems of different scales (macropores, small pores, and micropores). Segmented fractal characterization indicates that the fractal dimensions of large and small pores are greater than those of conventional sandstone. All the above analysis shows that the glutenite pore structure is the most complex. The fractal dimension of conventional sandstone has a good relationship with porosity and permeability, while the fractal dimension of glutenite samples has only a minor correlation with the storage capacity parameters. Hence, the glutenite has complex porosity-permeability relations, diverse types of pores and pore connectivity. The fractal dimension can characterize the reservoir capacity, but has certain limitation on seepage capacity characterization.

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    Geochronology and Geological Significance of Intrusive Rocks in the Bainaimiao Cu-Au Deposit, Inner Mongolia
    LÜ Zhao, WANG Jianping, WANG Jichun, XU Zhan, YUAN Shuopu
    Geoscience    2022, 36 (01): 307-320.   DOI: 10.19657/j.geoscience.1000-8527.2021.068
    Abstract768)   HTML6)    PDF(pc) (12302KB)(192)       Save

    The Bainaimiao Cu-Au deposit in Inner Mongolia is located in the continental marginal accretionary zone in the northern margin (middle section) of the North China Craton. Intrusive rocks are developed at Bainaimiao, with major lithologies including granodiorite, muscovite granite, and quartz diorite. LA-MC-ICP-MS zircon U-Pb dating indicate that the granodiorite was emplaced at (443.2±1.7) Ma and (447.6±1.8)Ma, the muscovite granite was formed at (429.1±2.7) Ma and (431.6±4.2) Ma, and the quartz diorite was formed at (424.5±2.0) Ma. Combined with the ore deposit geological characteristics, we considered that the Bainaimiao Cu mineralization occurred in the Late Ordovician-Early Silurian (432-447 Ma), related to the granodiorite emplacement. The Bainaimiao gold deposit was formed at about 430 Ma, which is related to the hydrothermal fluid enrichment brought by the muscovite granite emplacement. Under the Early Paleozoic subduction tectonics of the Paleo-Asian Ocean beneath the North China Craton, the porphyry Cu mineralization was dominated by the compression tectonics, whilst the epithermal Au mineralization occurred in a relatively extensional setting. Under the volcanic rock-magma process of the Bainaimiao island arc, the Bainaimiao Cu and Au mineralization constitutes an integral porphyry-epithermal mineral system.

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    Types and Causes of Longitudinal Extensional Faulted Anticline
    CHEN Fajing, CHEN Zhaonian
    Geoscience    2021, 35 (06): 1789-1796.   DOI: 10.19657/j.geoscience.1000-8527.2021.186
    Abstract765)   HTML4)    PDF(pc) (8450KB)(205)       Save

    Longitudinal extensional faulted anticline in extensional fault-bounded depression is an important oil and gas exploration field. According to faulted anticline geometry, these anticlines can be divided into double- faulted (a pair of normal faults) anticline, single-faulted anticline, and superimposed y-type faulted anticline. Based on Cenozoic geological data of the Bohai Bay Basin, origin of these three kinds of faulted anticlines is suggested as follow: (1) Double-faulted anticline is developed in rift valley stage, and is controlled by a pair of normal faults with face-to-face dipping mode. Its fault-bounded depression is mainly caused by local rock shortening during the early-stage regional extensional, differential subsidence and fault block tilting occurred in the late stage; (2) Single-faulted anticline is developed in the rift valley stage, and is controlled by single extensional fault-bounded depression. It is likely caused by the reverse traction, differential subsidence, and elastic flexure of rock formation during the descending process of the fault-bounded depression. Nonetheless local rock formation shortening is still a major factor; (3) Superimposed y-type faulted anticline is developed in post-rift stage and controlled by symmetric fault-bounded depression and the y-type faulted sag (i.e.fault-bounded sub-depression) among them. It is fundamentally different from the cause of strike-slip and extensional superimposed y-type faulted anticline, which does not actually belong to the longitudinal extensional faulted anticline category.

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    Geological Characteristics and Genesis of the Xiangtanzi Gold Deposit in Liangdang County, Gansu Province
    GAO Yinhu, YIN Gang, GONG Zeqiang, GUO Mingchun
    Geoscience    2021, 35 (06): 1523-1535.   DOI: 10.19657/j.geoscience.1000-8527.2021.127
    Abstract733)   HTML22)    PDF(pc) (10149KB)(127)       Save

    The Xiangtanzi gold deposit is located in the eastern West Qinling orogenic belt. The gold deposit is mainly controlled by NW-trending faults, and is closely related to the local intermediate-felsic dikes. Microscopic observation and electron microprobe analysis show that Au is mainly hosted in pyrite and arsenopyrite. The Co/Ni characteristics of pyrite in the ore body show that the genesis of pyrite is related to magmatism. Through REE analysis, it is found that REE characteristics of ore are basically consistent with those of rock mass, but obviously different from those of surrounding rock.The sulfur isotope of pyrite in the ore was tested and the ore sulfide δ34S values are from -5.7‰ to 2.0‰ (avg.0.38‰), clustering around zero with a tower distribution, which indicates that the ore sulfur source is magmatic. By hydrogen and oxygen isotope analysis, the Xiangtanzi gold ore has δ18${{\text{O}}_{{{\text{H}}_{2}}\text{O}}}$=3.44‰-9.65‰ (avg.6.29‰) and δD=-120.10‰ to -79.00‰ (avg.-100.47‰). This indicates that the ore-forming fluid in this area came mainly from magmatic water.Pb isotope characteristics indicates that the Pb evolution at Xiangtanzi was closely related to magmatism and orogeny. A comparative study shows that the metallogenic epoch of the Xiangtanzi gold deposit is late Indosinian. The Xiangtanzi gold deposit is a vein shaped ore body controlled by shallow fault system, which was invaded by magma containing ore-forming materials and fluids in the late Indosinian period. The discovery and genesis of Xiangtanzi gold deposit is of great significance to the prospecting direction in West Qinling area.

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    Hydrocarbon Accumulation Process and Exploration Potential in Linhe Depression, Hetao Basin
    SHEN Hua, LIU Zhen, SHI Yuanpeng, XU Zeyang, LI Yongjun, CHEN Shuguang, WANG Huilai, WANG Zhicheng, WANG Biao, LIU Chang
    Geoscience    2021, 35 (03): 871-882.   DOI: 10.19657/j.geoscience.1000-8527.2021.056
    Abstract715)   HTML13)    PDF(pc) (15509KB)(124)       Save

    The Hetao basin is a small-medium continental petroliferous basin in Midwest China. A million-ton oilfield was recently discovered in the Jilantai tectonic belt in the southwestern Linhe Depression. Due to the complex geological conditions and low degree of prospecting, the reservoir dynamic evolution is yet to be well understood. The reservoirs in the Jixi uplift belt and the central fault-barrier belt are taken as the main research target. Geological and seismic data were collected from comprehensive petroleum geological analysis, whilst dynamic analysis of the reservoir was performed by the “nine histories” analysis method. Three major findings are obtained: (1) the hydrocarbon accumulation timing was late and comprises three stages, i.e. the hydrocarbon generation, fault activity, and oil filling; (2) Quaternary strike-slip tectonism affected the oil accumulation. Negative flower-like structure was not developed, and the area with strong tectonic inversion in the late period is favorable for hydrocarbon accumulation. Meanwhile, the area with intense uplift and minor negative flowery structure is favorable for oil accumulation; (3) the southwest uplift belt and the central fault-barrier belt are selected as favorable exploration zone.

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    Sulfur and Lead Isotope Compositions of the Xiaohe Gold Deposit at Xunyang, Shaanxi Province, and Its Geological Significance
    MENG Wuyi, LIU Jiajun, WEI Liyong, ZHANG Zhen, WU Huanhuan, FAN Baocheng, PAN Yuan, LI Guoying, JIA Bin
    Geoscience    2021, 35 (06): 1587-1596.   DOI: 10.19657/j.geoscience.1000-8527.2021.115
    Abstract713)   HTML10)    PDF(pc) (8765KB)(103)       Save

    The Xiaohe is a medium-sized gold deposit discovered in the central belt of the South Qinling Orogen in recent years. The ores are fine-disseminated, and the orebodies are controlled by both strata and structures. Based on field work, four metallogenic stages are divided according to mineral assemblages and crosscutting relationships: Ⅰ. Quartz veins with little sulfide in early-ore-stage; Ⅱ. Quartz veins with main-ore-stage pyrite and arsenopyrite in main mineralization stage; Ⅲ. Quartz veins with main-ore-stage polymetallic sulfides; Ⅳ. Late-ore-stage calcite and quartz veins. Stage Ⅱ and Ⅲ are the main gold mineralization stages. In situ sulfur isotope analysis show that the δ34S value of stage Ⅰ pyrite=20.80‰-25.77‰ (avg.23.59‰), stage Ⅱ pyrite and arsenopyrite=15.46‰-19.12‰ (avg.17.5‰), stage Ⅲ galena and sphalerite=11.35‰-16.78‰ (avg.13.88‰). This indicates that the sulfur is mainly sedimentary-sourced, and there is continuous addition of low-δ34S hydrothermal fluid during the ore-forming process. The sulfide Pb isotope analysis yielded 206Pb/204Pb=17.882,1-18.367,4, 207Pb/204Pb=15.614,0-15.674,1, and 208Pb/204Pb=38.016,3-38.934,2, indicating that the lead was derived mainly from the crust with certain mantle input. Based on the deposit geological and S and Pb isotope characteristics, we suggest that fluid mixing occurred in the Xiaohe gold mineralization.

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    Zircon Saturation Temperature and Titanium Temperature and Geological Significance of Granites in Shangqimugan, West Kunlun Orogen
    CHEN Haiyun, SUN Xiaodong, ZHANG Zhi
    Geoscience    2021, 35 (05): 1206-1217.   DOI: 10.19657/j.geoscience.1000-8527.2021.036
    Abstract702)   HTML35)    PDF(pc) (2211KB)(203)       Save

    In this study, we conducted zircon trace element and whole-rock major element analyses on the Shangqimugan granites, and calculated the zircon saturation temperatures and titanium temperatures, which can unravel the temperatures of the source magma, and the formation environment of granite is further analyzed. Our zircon samples present typical igneous zircon REE left-inclining patterns. Besides, LREEs are obviously depleted and HREEs enriched. The samples have distinct negative Eu anomalies and positive Ce anomalies. The results indicate that the zircon saturation temperatures for the Shangqimugan granites are at 772-829 ℃ (average 800 ℃), which belong to high-temperature granite. The minimum Ti-in-zircon average temperature is 614 ℃, the maximum average temperature is 634 ℃, and the zircons were formed at 614-634 ℃ in the granites. Combining with zircon trace elements characteristics, the zircon saturation temperatures and the correlation between titanium temperature with Th/U and 10000/Hf, we suggested that the Shangqimugan granites were formed by delamination of the thickened lower lithosphere led by mantle underplating in the West Kunlun Orogen. During the magma fractionation, zircon has recrystallized and multiphase magma (melts-fluids) replenishment may have occurred. The heat source of magma was probably related to the asthenospheric upwelling (mantle underplating), which occurred during the post-collision intraplate extension at the end of Qiangtang-Tarim plate convergence along the Kangxiwar fault.

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    Geomagnetic Field Distribution Characteristics of Xiaoshan Volcano and Its Geological Significance
    LI Zhaoling
    Geoscience    2021, 35 (05): 1480-1486.   DOI: 10.19657/j.geoscience.1000-8527.2020.071
    Abstract693)   HTML9)    PDF(pc) (8037KB)(92)       Save

    Located on the Bohai seashore, the Xiaoshan volcano is the direct evidence of crustal activity on the western Bohai seacoast. The area is famous for its typicality, diversity and naturalness. With its unique scienti-fic significance, it is very rare in China. Due to the extensive Quaternary cover on the volcanic rocks, high-precision magnetic measurement was used to delineate the boundary of volcanic relics and to study typical geological structures. In this study, we described the magnetic field distribution characteristics of the Xiaoshan volcanic geological relics protected zone. Distribution range of the magmatic and sedimentary rocks in the zone was identified and their boundaries were delineated, and a number of faults were inferred. This is achieved through analyzing magnetic anomaly of the pole, upward extension, and the search for derivative and other processing methods. Our findings support that the high-precision magnetic method is effective to study the geological characteristics beneath the overburden area. The study of the magnetic field distribution features provides detailed and reliable basic data for the Xiaoshan volcano geological relics, and has important implications for the division of the geological relic landscape and for sensible planning of the protected zone.

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    Records of Mesozoic-Cenozoic Collision Orogenic Events on the Western Margin of the Yangtze Platform:Geochronology Evidence from Zircon U-Pb Isotope of Emeishan Basalt
    ZHANG Honghui, YUAN Yongsheng, YU Yangzhong, LI Hong, ZHANG Liyuan, LI Zhiwei, GUO Taitang, PAN Jiangtao, ZHAN Huasi, SHI Haitao
    Geoscience    2021, 35 (05): 1155-1177.   DOI: 10.19657/j.geoscience.1000-8527.2021.107
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    Using LA-ICP-MS technique,the U-Pb isotope determination of zircons in the Emeishan basalts in Tangdian, of eastern Yunnan on the western margin of the Yangtze Plate is carried out. The distribution range of 363 age data is (14.9±0.6)-(3,023±50) Ma, spanning a long geological age, its 11 age peaks are 750~850 Ma, ~450 Ma, ~275 Ma, ~260 Ma, ~247 Ma, ~215 Ma, ~160 Ma, ~120 Ma, ~100 Ma, ~52 Ma and ~35 Ma, respectively, reflecting that Emeishan basalt experienced the contamination of crustal materials in the formation process, and being affected by later tectonic thermal events. The first and second sub-circle of the Emeishan basalt were formed at (259.9±3.2) Ma and (259.2±3.6) Ma, respectively. The zircon ages of the basalts of ~275 Ma may represent the age of the formation age of Emeishan basalt magma chamber and the time when the crust began to uplift due to Emei mantle plume event.After the formation of the Emeishan basalt, the western margin of the Yangtze Plate experienced successively tectonic thermal events of ~247 Ma, ~215 Ma, ~160 Ma, ~120 Ma, ~100 Ma, ~52 Ma, and ~35 Ma. These age data are the time records of the Mesozoic Cenozoic collision orogenic event reaching the peak of temperature and pressure on the western margin of the Yangtze Plate.

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    Metallogenic Regularities and Future Prospecting Direction of Gold-Copper Deposits in the Zhashui-Shanyang Orefield, Southern Qinling Orogen
    WANG Ruiting, JI Yuefei, CHENG Huan, LIU Kai, ZHANG Qi, LI Xian, REN Tao
    Geoscience    2021, 35 (06): 1487-1503.   DOI: 10.19657/j.geoscience.1000-8527.2021.123
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    In the Zhashui-Shanyang orefield (Southern Qinling Orogen),structure deformation and magmatic activity were strong,and the ore deposits (prospects) are distributed in groups and belts,and the metallogenic conditions are favorable. Based on long-term prospecting practice, analysis of geological and metallogenic setting and typical deposit profiles,we considered that local gold deposits are mainly controlled by EW-trending faults or ductile-brittle shear zones and NE-trending tensional-torsional superimposed structure.The Cambrian Shuigou, Devonian Xinhongpu and Dafenggou Formations are the gold-bearing strata. The gold orebodies are distributed approximately equidistant from east to west,and individual orebodies are lenticular, dumbbell-shaped or vesicular along strike.The orebodies are characterized by pinch-out reproduction, and thick and high-grade in the structurally superimposed area. Local gold deposits are mostly of meso epithermal hydrothermal type and distal low- temperature hydrothermal type. The metallogenic epoch is Indosinian-Yanshanian period. The deep and periphery,the intersection of EW and NNE trending faults near the secondary regional faults,the fault bends and the structural collapse sites are favorable targets for gold prospecting at Xiajiadian and in other known gold deposits. The copper deposits are distributed on both sides of the Sanyang-Fengzhen fault. The main metallogenic type is porphyry-skarn type,followed by tectono-hydrothermal transformation type and cryptoexplosive breccia type. Porphyry-skarn Cu(Mo) deposits are controlled by the Yanshanian tectono-magmatic activity. Occurring in the contact zone between porphyry body and wallrock in the Yanshanian period,the orebodies are mostly controlled by the contact between intrusions and wallrocks,and appear as layers or lenses. The small intermediate felsic stock and their contact with the Yanshanian wallrocks, and the vicinity of the EW 3rd order fault zone are preferred targets for Cu (Mo) exploration. In this study,the regional metallogenic model of the gold-copper deposits is established,and the prospecting criteria are summarized for the Zhashui-Sanyang orefield. Based on the systematic analysis of metallogenic regularity, mineralization,geophysical/geochemical prospecting,and remote sensing anomalies,we considered that there is great ore prospecting potential, and we proposed three Au-Cu(Mo) prospecting areas,as well as the future prospecting directions.

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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
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    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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    Controlling Factors of Thick Glutenite Reservoir Accumulation in Hetao Basin: A Case Study of Jihua-2X Reservoir, Linhe Sag
    WANG Huilai, SUN Ruina, ZHANG Ruifeng, LIU Xiheng, LIU Jing, TIAN Sisi, XIAO Jinxia
    Geoscience    2021, 35 (03): 861-870.   DOI: 10.19657/j.geoscience.1000-8527.2021.058
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    In the Meso-Cenozoic Hetao Basin, the early-stage wells have oil and gas shows but there is no substantial exploration breakthrough. The discovery of thick glutenite reservoir layer of Jihua-2X indicates good exploration prospect in the basin. To understand the hydrocarbon accumulation characteristics and delineate favorable exploration targets in the basin, we took the Jihua-2X reservoir as a research target. The major controlling factors on the accumulation of thick glutenite reservoir layers was clarified by analyzing the Jihua-2X reservoir, which is located in the eastern wing of the Jilantai tectonic belt (west of the Linhe depression). It is an inherited nose structure controlled by the Langshan branch fault. The oil-bearing sandstone is the fan delta sandbody in the Paleogene Linhe Formation and Cretaceous Guyang Formation. The Jihua-2X reservoir is well-developed and has high degree of enrichment. Matured source rocks of the Guyang Formation in the sub-sag area with high hydrocarbon expulsion power is necessary for hydrocarbon accumulation in the Jihua-2X trap. Furthermore, fan delta reservoir with high sand-strata ratio and successive nose structure, and interconnected migration pathway was likely the key for hydrocarbon accumulation in the Jihua-2X trap. Our results can provide a geological foundation for future exploration in the Hetao basin.

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    Screening of Marine Urease-producing Bacteria and Characterization of Their Produced Calcium Carbonate Minerals
    CHEN Huijia, ZHANG Huiqing, FENG Ying, WEI Shiping
    Geoscience    2022, 36 (01): 212-220.   DOI: 10.19657/j.geoscience.1000-8527.2021.170
    Abstract627)   HTML13)    PDF(pc) (2889KB)(177)       Save

    Urease-producing bacteria are widespread in nature, and the calcium carbonate biomineralization induced by these bacteria are widely used in various geological and engineering fields. This study aims to isolate the urease-producing bacteria from marine sediments, and to characterize the produced calcium carbonate crystals. The results may have potential applications in the geological and engineering fields. A total of 33 bacterial strains were isolated from the marine sediments sampled from Beidaihe (China), among which 10 bacterial strains were identified to produce urease. The 16S rRNA gene sequence analyses show that three strains belong to the Ochrobactrum genus, and the other seven strains belong to the Lysinibacillus genus. Two strains, O. anthropic CP57 and L. fusiformis CP66, were selected to characterize their calcium carbonate formations. The SEM, XRD, and SAED results show that the calcium carbonate formed by CP57 is irregular-shape calcite, whereas that formed by CP66 is irregular-shape or spherical calcite and vaterite. Further FTIR characterization of the bacterial calcium carbonate shows that the spectrum of CP57 at the wave numbers of 1,422 cm-1, 711 cm-1 and 875 cm-1, correspond to the typical absorption peaks of calcite. However, exception appears in the FTIR spectrum of CP66, with two extra peaks at 1,081 cm-1 and 743 cm-1 clearly attributed to vaterite. Our results provide a foundation to reveal the mechanism of different morphologies and mineral phases formed by various bacteria.

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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
    Abstract600)   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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    Sediment Transport Characteristics of Mountainous Rivers in Different Climatic Zones of Coastal China
    SUN Shuang, HU Ke, LI Yan, YANG Junpeng
    Geoscience    2022, 36 (01): 68-76.   DOI: 10.19657/j.geoscience.1000-8527.2021.162
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    In recent years, many studies have found that small mountainous rivers have instantaneous enormous flux, strong response to extreme climate events, and rapid sediment transport. However, the effects of mountainous rivers on global sediment transport have been underestimated due to the lack of adequate monitoring data and system summary. There are still inadequate studies on the mountainous rivers with different river-ocean and weathering-transportation from the mega-river systems. Revealing the sediment transport characteristics of different climates in the common natural and anthropogenic influence would help to understand the Earth’s surface processes and the global land-sea interactions. This paper summarizes the global soil carbon content, as well as meteorological, hydrologic, and mineralogical data of mountainous rivers of the different climatic zone in the coastal China region. We summarized that: (1) Soil organic carbon content of the mountainous river basins is high in China, and the primary productivity of the tropical mountainous river basins is higher than that in the temperate basins, thus the soil organic carbon content of the former is also higher. Among the tropical basins, the river relief in Taiwan, China is the highest, hence its soil organic carbon content is very high in China. In addition, the rapid sediment transport to the estuary and coastal zone by mountainous rivers has greatly improved the burial efficiency of organic carbon, therefore it represents a significant component of the global organic carbon source and sink; (2) Regardless temperate or tropical climatic zone, the mountainous rivers have strong response to extreme climate. Furthermore, the smaller the watershed area and the steeper the river terrain, the stronger the river responds to extreme climatic events; (3) Regardless of the tectonic activity intensity, the mineralogical characteristics of the mountainous rivers can accurately indicate the source information in sediments. Moreover, sediments from the rivers in low-relief and tectonic stable zone can record more detailed climatic characteristics; (4) Sediments in mountainous rivers are very sensitive to human activities, while the sedimentary environment influence from existing human activities is far lower than in the mega-river basins.

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    Grain Size Characteristics and Sedimentary Dynamics of Sedimentary Column of Mangrove Wetland in Zhanjiang Bay
    LUO Songying, QUAN Xiaowen, CHEN Bishan, QIU Jinkun, LIANG Jiaxin, DENG Ziyi
    Geoscience    2021, 35 (03): 647-656.   DOI: 10.19657/j.geoscience.1000-8527.2020.101
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    Granularity is an important parameter for understanding the sedimentary dynamics characteristics. Mangrove wetland sediments host much sedimentary environment information during the transport and deposition processes. To unravel the vertical grain size characteristics and sedimentary dynamics of mangrove wetland in the Zhanjiang Bay and enhance wetland ecological protection, the grain size parameter characteristics, frequency distribution curve, and sedimentation rate of mangrove wetland sedimentary columns at the Nanhaidi (NHD), Dongtoushan Island (DTSD), Huguang Town (HGZ)and Guanhaichanglang (GHCL)stations were analyzed. Our work reveals the sedimentary evolution of the Zhanjiang Bay in the past century, and our results suggest that: (1)The 210Pbex specific activity of NHD and DTSD columns both show a good exponential decay trend, with the deposition rate increasing with time. The average deposition rates of NHD and DTSD were 1.277 cm/a and 1.034 cm/a, respectively, but that of DTSD far exceeded that of NHD after 2011. (2)Grain-size characteristics of individual sedimentary column is markedly different, and the average grain size of NHD sedimentary column is 3.42ϕ, mainly composed of sand (67.23%)and is classified as silty sand. The mean diameter of DTSD is 5.71ϕ with sorting coefficient of 2.21. It is mainly composed of silty-sand (55.13%)and is classified as sandy-silt. HGZ is sandy-silt with mean particle size of 5.49ϕ. The GHCL is mainly composed of sand (55.85%)with average particle size of 4.18ϕ. (3)The grain size frequency distribution curves display multimodal features, implying that the deposition process was doped with the process of various sedimentary media. The NHD and GHCL particle sizes are clustered toward the sandy particle end-member, indicating strong sedimentary dynamics, whereas the sedimentary dynamics of DTSD and HGZ is considerably weaker. (4)The grain-size characteristics are influenced by the local terrestrial source, island and runoff, whilst the sedimentation process is significantly influenced by the tidal current dynamics, mangrove distribution, and human activities. In recent years, the rising sedimentation rate in the Zhanjiang Bay may have an impact on the navigation channel, and more attention should be paid to the wetland ecological environment in the bay.

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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
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    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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    Geochemical Characteristics and Prospecting Indication of Ore-bearing Rocks in the Hongtoushan Copper-zinc Deposit, Liaoning
    WU Xiaolei, CHANG Jinyang, ZENG Nanshi, XU Wenjie, TAO Mingrong, ZHAO Gang, HAN Jian
    Geoscience    2022, 36 (01): 362-377.   DOI: 10.19657/j.geoscience.1000-8527.2022.01.32
    Abstract570)   HTML6)    PDF(pc) (7649KB)(129)       Save

    The Hongtoushan copper-zinc deposit, located in the Archean greenstone belt, is a massive sulfide deposit. The ore-bearing rocks are composed of hornblende plagiogneiss, hornblende (quartz) plagiogneiss, biotite plagiogneiss, biotite (quartz) plagiogneiss, and biotite quartz gneiss. It suggests that protoliths of these metamorphic rocks are volcanic rocks based on protolith restoration and discrimination of tectonic environment. Among them, protoliths of the hornblende plagiogneiss and hornblende (quartz) plagiogneiss are basic volcanic rocks, whereas protoliths of the biotite plagiogneiss, biotite (quartz) plagiogneiss, and biotite quartz gneiss are intermediate-acid volcanic rocks, together they were the products of the bimodal volcanics. In order to best reveal the possibility of geochemical parameters of the ore-bearing rocks as prospecting indicators, based on the major elements, rare earth elements and trace elements of the ore-bearing rocks, the authors found that the Cu (290.82 μg/g), SiO2 (57.24%), total rare earth elements (ΣREE) concentration (53.78 μg/g), and LREE/HREE ratio (4.29) of the hornblende (quartz) plagiogneiss, while the Cu (88.09 μg/g ) and SiO2 (70.50%) concentrations of the biotite (quartz) plagiogneiss and biotite quartz gneiss can be used as important prospecting indicators for the Hongtoushan copper-zinc deposit.

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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
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    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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    Groundwater Renewability Study Based on Tritium (3H) in the Middle and Lower Watershed of Anyang River
    HUANG Xiangui, PING Jianhua, YU Yan, ZHU Yaqiang, ZHANG Min
    Geoscience    2021, 35 (03): 693-702.   DOI: 10.19657/j.geoscience.1000-8527.2020.066
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    Groundwater renewable ability in the middle and lower watershed of Anyang River are studied by analyzing the tritium concentration of water, groundwater age and mean annual renewal rate (MARR). The MGMTP is employed to reconstruct the 3H concentration of atmospheric precipitation in the study area (1953-2016), whilst the groundwater age and MARR of phreatic water and springs are assessed via Lumped Parameter Modelling (LPM) and the method developed by Le Gal La Shalle et al., respectively. The results indicate that: (1) Phreatic water and springs received atmospheric precipitation recharge over the past 20 years, and the recharge and flow condition of the unconfined groundwater extended widely due to the regional hydrogeological control. (2) The mean residence time of the Xiaonanhai spring is 23 years, associated with 3.6% of MARR and its flux has been attenuating. (3) Unconfined groundwater in the empennage of the Anyang River alluvial/proluvial fan and recharge area has considerable renewable capacity, as it received direct recharge from infiltrated atmospheric precipitation and surface water leakage. Groundwater from the middle zone of the fan to the Beijing-Hongkong-Macao highway is 40-60 years old, and is largely sourced from modern atmospheric precipitation. Nevertheless, that in frontal belt of the fan has very low renewable capacity due to its mixing nature between modern groundwater and older input, with average age not younger than 60 years. (4) Deep confined groundwater in both the eroded hills and alluvial and flood plain is very old and has thus low renewability. This indicates that protection of the Xiaonanhai spring should be increased, and considerable achievement should be obtained in short period of time. The underground water depression cone in the Anyang city urban area has been substantially shrunk by the water supply from the Middle-Route of South to North Water Transfer Project, and the restriction on groundwater exploitation.

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    Variations of Organic Carbon and Evaluation of Carbon Sequestration Potential in Surface Soil in Songnen Plain of Heilongjiang Province from 1986 to 2019
    ZHANG Li, JIN Jingze, JIANG Xia, MAO Long, CUI Yujun, LI Ying, WANG Enbao
    Geoscience    2021, 35 (04): 914-922.   DOI: 10.19657/j.geoscience.1000-8527.2021.02
    Abstract568)   HTML10)    PDF(pc) (2968KB)(233)       Save

    Soil organic carbon (SOC)is a key index to evaluate soil fertility and soil C sequestration. Therefore, it is important to study variations in SOC to accurate assessment of regional soil C sequestration potential and sustainable utilization of soil resource. Based on the Second National Soil Survey and the data derived from the soil profiles measured from the farmland in 2019, we analyzed the temporal and spatial variations of soil organic carbon density (SOCD)in the surface layer (0-20 cm)in Songnen Plain of Heilongjiang Province, via the GIS spatial analysis technique, and estimated the soil organic carbon reserves using the soil type method and the potential of soil carbon sequestration using the balance method. The results show that the surface SOCD decreased by 1.06 kg/m2 on average over the past 30 years, the area with the decrease of SOCD mainly distri-buted in the middle and southeast of Songnen Plain in Heilongjiang Province. The surface SOC reserves decreased by about 143.99 Tg. Soil types with more decrease of SOC were meadow soil, chernozem and black soil, which accounted for 84.55% of the total decrease of SOC. The current Songnen Plain had a carbon sequestration potential of -2.08 Tg, including dark brown soil, albic soil and black soil is a positive potential, and the other soil types are a negative potential. It is suggested that the potential of soil carbon sequestration in Songnen Plain should be improved by increasing the application of organic fertilizer, returning straw to the field, and promoting the cultivation method of no tillage and less tillage.

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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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    Investigation and Evaluation on Environmental Quality of Heavy Metals in Sediments of the Inland Bay of Shantou City, Guangdong Province
    LI Jinzhe, LIU Ningqiang, GONG Qingjie, LI Chengzhu
    Geoscience    2021, 35 (05): 1441-1449.   DOI: 10.19657/j.geoscience.1000-8527.2021.047
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    The environmental quality of sediments in inland bay is closely related to the survival of aquatic organisms and human health. Forty-six samples are collected from surface and deep sediments in 23 locations of cross-gulf in the Inland Bay of Shantou City in Guangdong Province. The pH values, the concentration of 7 heavy metal elements, Cd, Hg, As, Pb, Cr, Cu and Zn, and the content of K are analyzed to evaluate the environmental risk of heavy metals in these sediments with reference to soil contamination risk of paddy field in agricultural land. The results show that the pH of sediments in Shantou Inland Bay is between 7.00 and 8.82, with an average value of 7.83. Among 46 samples, 41 samples have pH values greater than 7.5. The contents of 7 heavy metals in the sediments of Inland Bay are obviously lower than their environmental pollution control values, which means there is no need to control the environmental pollution of heavy metals in the sediments. The contents of Cd, As, Pb and Cr are all lower than their screening values of pollution risk, and their pollution risk could be ignored. The concentrations of Hg in 2 surface samples were higher than the screening value of pollution risk, and the contents of Cu and Zn in 18 samples were higher than their screening values of pollution risk. Therefore, it is suggested to monitor the concentrations of Cu, Zn and Hg in these sediments. The content of K is between 0.70% and 2.59%, with an average value of 1.54%. Based on the comparison of elemental contents between surface layer and deep layer sediments it is concluded that the pollution source of Hg in this area should be anthropogenic. However, the pollution sources of Cu and Zn may be anthropogenic or mixed resulted from anthropogenic and natural resources.

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    Characteristics, Genesis and Evolution of Daigu Landform in Yimengshan UNESCO Global Geopark
    CAI Yinlu, WU Fadong, HAN Jinfang, HUANG Zhen, ZHOU Ying, LIU Baoyin, CHEN Yangyang
    Geoscience    2023, 37 (04): 1065-1074.   DOI: 10.19657/j.geoscience.1000-8527.2023.085
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    The Yimengshan UNESCO Global Geopark (UGGp) is the origin of the “Daigu Landform”. Through field investigation of the characteristics of Gu landform, based on the measurement of river valley stratigraphy and profiles, and using the OSL dating of the river terrace to calculate the cutting rate, the formation time of Daigu Landform has been determined. The results show that the geomorphological features of the Daigu Landform are related to the strata lithology of the Gu body. Daigu Landform is a type of mesa structure, with a flat top, steep margin and gentle slope. Gu body is mainly composed of two strata with different lithologies: The top comprises Cambrian limestone with strong weathering resistance but develops many joints, while the Gu body with weak erosion resistance is dominated by mudstone and siltstone. We estimated that the formation time is about 1.77 Ma by using the erosion rate, based on the dating results of the river terrace. The Daigu Landform formation and evolution can be divided into four main stages: (1) the material was formed in the Early Cambrian; (2) tectonic uplift, and the strata gradually exhumed and the shaping stage began; (3) long-term weathering and denudation of various external forces, such as surface water that gradually created the mature Daigu Landform; (4) the landform ended its development when the upper limestone collapsed. The systematic study of the Daigu Landform has great importance in understanding the Daigu Landform and its scientific value, which also contributes to the spreading of geoscience knowledge of UGGps.

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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
    Abstract553)   HTML3)    PDF(pc) (11199KB)(270)       Save

    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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    Geochronology and Glaciation of the Neoproterozoic Diamictite in Aksu Area, Northwestern Margin of the Tarim Block
    LI Wangpeng, WANG Yi, LI Huili, ZHANG Zhongpei, LIU Shaofeng, YANG Weili, CAI Xiyao, NIE Haikuan, QIAN Tao, LI Xiaojian
    Geoscience    2022, 36 (01): 27-47.   DOI: 10.19657/j.geoscience.1000-8527.2021.067
    Abstract549)   HTML12)    PDF(pc) (9856KB)(131)       Save

    Age correlation of the Neoproterozoic glaciation events in the Tarim Block remains controversial, and obtaining reliable deposition time for the Neoproterozoic diamictite is crucial.Two sets of the Neoproterozoic diamictite were developed in Aksu area along the northwestern margin of the Tarim Block. Petrologic and whole-rock geochemical analyses and radiometric dating were conducted to define the sedimentary rock assemblages,deposition time, and paleoclimatic weathering conditions. The chemical index of alteration (CIA) indicates that the Qiaoenbrak and Yuermeinak Formations represent two distinct glaciation episodes, and two secondary glaciation events exist in the Qiaoenbrak glaciation.Detrital zircon U-Pb dating of the glacial deposits and their adjacent beds indicate that the Qiaoenbrak glaciation in Aksu started along the northwestern margin of the TarimBlock after (719±10) Ma, whilst the Yuermeinak glaciation did not start before (685±11) Ma, and its cessation timing can be constrained by the top boundary age of the Nanhua System (635 Ma) or the U-Pb age of the overlying Sinian Sugetbrak Formation basalt (615±5 Ma).Comprehensive analyses of isotope geochronology, geochemistry, and sedimentology indicate that the Qiaoenbrak glaciation (Aksu area) corresponded to the Altungol glaciation (Quruqtagh area), the Jiangkou glaciation (South China), and the Sturtian glaciation (global). Meanwhile, the Yuermeinak glaciation (Aksu area) corresponded to the Tereekan glaciation (Quruqtagh area), the Nantuo glaciation (South China), and the Marinoan glaciation (global). Glaciation, isotopic geochronology, and geochemistry can provide a basis for the division and comparison of the Neoproterozoic sequences in the Tarim Block.

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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)(324)       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 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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    Practice and Thinking on the Study of “Sea-Land Correlation”
    FANG Nianqiao
    Geoscience    2022, 36 (01): 1-13.   DOI: 10.19657/j.geoscience.1000-8527.2021.171
    Abstract532)   HTML22)    PDF(pc) (10021KB)(215)       Save

    In this paper the author shares his two important scientific experiences and results on “Sea-Land Correlation”: (1) to research the Himalayan and Tibetan uplift based on data from the NE Indian Ocean, and (2) to research the closure of the “proto-South China Sea (SCS)” and the birth of the SCS based on magmatic-sedimentary records from their neighboring landmasses. The unique sea-land correlation provides an effective access on the understanding of regional evolution. In the first study of monitoring the mountain uplift based on marine deposits, two highly-distinct (in composition and origin) deep-sea sedimentary sequences are discriminated. Located on the Bengal submarine fan and Ninetyeast Ridge, respectively, each sequence has its own respond signals to the Himalayan and Tibetan uplift. By strictly sieving and correlating the proxies from those sequences, this study argues that the most important periods of the uplift of the Himalayan Mountain and Tibetan Plateau occurred since Late Miocene, at 3.6-3.2 Ma and 1.0-0.6 Ma. In the second study of approaching the seas from the continental materials, highly complicated records including magma, structure, sedimentation and logging, whose preserved condition is usually inferior to those records collected from the deep sea, need to be dealt with. The advantage of such study is that researchers are permitted to organize multidisciplinary materials in a large region, and set up the regional evolutionary framework based on land-sea integration, thereby avoiding limitations brought by a single submarine drilling hole. In the southern margin of China continent there was a subversive change from the Late Mesozoic active pattern to Cenozoic passive pattern. To reconstruct systematically a Mesozoic marginal arc,the author established a cross-shaped investigation approach: searching for the extension of arc discovered in Hainan Island in the E-W direction and finding out the arc architecture in the N-S direction. It is found that a drastic regional uplift resulting from the plate convergence occurred in the Mid Cretaceous time (110-80 Ma), and its intensity weakened northward. As compared with the contemporaneous tectono-sedimentary records outcropped in the Zhejiang-Fujian continental margin, the “proto-SCS” subducting northward during the Late Mesozoic was probably affiliated to the deceased Tethyan domain. Since the end of Mesozoic, the margin of South China has entered a completely new phase. With the largest and best-preserved Cenozoic magmatic-sedimentary records, the Sanshui basin is selected as a focus to study the rupturing of the passive margin. During the Late Paleocene (~57Ma) the alkaline bimodal volcanism, represented by alkaline basalt, trachyte and comendite, extensively developed in the study area and continued to the ending of the basin (42-38Ma). The deduction can be achieved from the experimental data: (1) magma sources were derived from the asthenospheric mantle, and both the large-scale trachyte and comendite were also resulted from the phased crystallization differentiation of mantle-derived basaltic magma, and (2) the calculated mantle thermal anomaly is indistinct. The available evidences lead to the following interpretations: There is no deeply-derived mantle plume dominating regional tectonism. The volcanic rock suites developed in the Sanshui basin actually imply that the subduction-collision occurring in the Late Mesozoic had shortened and thickened the lithosphere, and the consequent lithospheric delamination and asthenospheric upwelling occurred around the Mesozoic-Cenozoic boundary. This tectonic mechanism not only resulted in the Early Cenozoic rifting in South China but also likely had an impact on the subsequently spreading of the SCS. Ocean and land, the two largest units on the Earth, are being closely connected by modern geosciences. Collecting relevant geological signals from the ocean to study continental evolution, or vice versa, can provide us with a new and effective window to examine and solve scientific problems.

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    Hydrogeological Features and Groundwater Enrichment Model of Paleogene Zhujiagou Formation in Lower Chaiwen River Valley, Shandong Province
    LI Bo, WU Xuan, ZHANG Yifei, XU Congcong, LIU Chunwei, GUAN Qin, LUO Fei
    Geoscience    2021, 35 (03): 675-681.   DOI: 10.19657/j.geoscience.1000-8527.2020.041
    Abstract530)   HTML11)    PDF(pc) (4162KB)(158)       Save

    The Paleogene Zhujiagou Formation in south-central Shandong comprises a molassic sequence dominated by calcareous breccia, and has markedly varying water-yield properties caused by faults. Based on the regional hydrogeological survey in lower Chaiwen River valley, the aquifer characteristics, water-yield properties, and groundwater hydrochemical characteristics are analyzed. The results show that the Zhujiagou Formation comprises calcareous cemented calcirudite, and karst is developed above 90 m depth with single-well yield of 100-300 m3/d, locally reaching >300 m 3/d. Groundwater in the fissured or karst aquifers in the southern Wenkou Basin are similar, indicating close interactions between the two. The Gibbs map demonstrates that the groundwater hydrochemical features are dominated by rock-weathering, and evaporation and concentration. The ions in the groundwater are mainly sourced from rock dissolution and anthropogenic pollution. Based on drill-hole data analysis, the groundwater enrichment model is a fracture-type calcirudite karst-fissure water storage one, and we consider that fractured clastic rocks can be used as an emergency water exploration target.

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    Spatial Distribution Characteristics and Influencing Factors of Soil Lead in Jieyang City, Guangdong Province
    ZANG Chuanzi, WEN Hanhui, CAI Limei, LUO Jie, XU Shubang, MEI Jingxian
    Geoscience    2021, 35 (05): 1425-1432.   DOI: 10.19657/j.geoscience.1000-8527.2021.24
    Abstract527)   HTML12)    PDF(pc) (4701KB)(121)       Save

    Taking the soil in Jieyang City as the research object, 1,330 surface soil samples (0-20 cm) and 331 deep soil samples (>150 cm) were collected, and the Pb content in soil was determined. GIS spatial ana-lysis technology, semivariogram fitting and variance analysis were used to study the spatial structure, distribution characteristics and influencing factors of soil Pb content. The results showed that there was no obvious Pb pollution in Jieyang city, and the average Pb content in surface soil was 39.26 mg/kg, which was lower than the background value of Pb in Jieyang City (43.71 mg/kg) and slightly higher than that in Guangdong Province (36.00 mg/kg). Enrichment factors showed that the enrichment degree of Pb in the surface soil of the study area is mainly no enrichment and slight enrichment, accounting for 52.11% and 42.63%, respectively, and Pb enrichment is not significant; The spatial distribution of Pb in the surface soil of the study area showed mode-rate autocorrelation. The Pb high value areas of surface soil are mainly distributed in the eastern and southern parts where human activities have a strong influence. According to the classification statistics of land use, soil parent material, soil type and its physical and chemical properties, the Pb content in surface soil of woodland and unused land is the highest; The Pb content in the soil formed by shale weathering is significantly higher than that of other soil-forming parent materials; Pb content in yellow soil is relatively high; Organic carbon and pH were positively correlated with Pb content in soil.

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