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    10 February 2022, Volume 36 Issue 01
    Marine Geology
    Practice and Thinking on the Study of “Sea-Land Correlation”
    FANG Nianqiao
    2022, 36(01):  1-13.  DOI: 10.19657/j.geoscience.1000-8527.2021.171
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    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.

    Water Evolution of Nuomuhong Shell Ridge in Qaidam Basin: Evidence from Ostracods
    LI Wei, QU Haiying, LI Sha, ZHOU Shumin, SONG Xianteng, WANG Xiaonan
    2022, 36(01):  14-26.  DOI: 10.19657/j.geoscience.1000-8527.2021.025
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    As a rare and distinctive geomorphological feature in arid regions around the world, a shell ridge in the Qaidam Basin preserves many bivalve fossils of different sizes and articulated shells, which provides important record for the paleoclimate and paleoenvironmental evolution of the middle-late Pleistocene NE Tibetan Plateau. The Nuomuhong Shell Ridge is newly discovered as fluvial sediments, which is different from early studies of lacustrine deposits. Through systematic analyses, we established eight ostracod assemblages for the Shell Ridge. Though scarce ostracod fossils were found in Assemblage 1 and they were hardly identified, fossils in other assemblages were relatively abundant. We named Assemblage 2 to 8 as follows: Ilyocypris-Candona-Candoniella, Ilyocypris-Candona-Leucocythere-Candoniella-Eucypris inflate, Leucocythere-Ilyocypris, Ilyocypris-Leucocythere-Candoniella-Candona, Ilyocypris-Candoniella-Leucocythere, Ilyocypris bradyi-Ilyocypris echinata and Ilyocypris bradyi-Candoniella. We clarified water evolution of the Shell Ridge based on ostracod fossil characteristics and their paleoecology information. We identified the Nuomuhong Shell Ridge fluvial deposits that went through frequent river diversions within the Assemblage 1 to 5 occurrence, during which the shell ridge sedimentation fluctuated between oxbow lake and shallow river environments. The shallow river environment was favorable for the living of ostracods, whereas the deeper water of oxbow lake was detrimental to their survival. The shallow river condition continued through the time of Assemblage 6 to 8, during which ostracods thrived in warmer climate till the river enclosed and salinity increased, which hampered ostracod survival. Subsequently, salt crust was likely formed after persistent droughts and the deposition of Nuomuhong Shell Ridge ended.

    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
    2022, 36(01):  27-47.  DOI: 10.19657/j.geoscience.1000-8527.2021.067
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    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.

    Sedimentary Environment and Tectonic Significance of the Upper Triassic Rigain Pünco Formation in the Rongma Region, Tibet, China
    CHEN Yaofei, HOU Engang, GAO Jinhan, XIAO Hongji, WANG Genhou
    2022, 36(01):  48-57.  DOI: 10.19657/j.geoscience.1000-8527.2021.164
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    The Upper Triassic Rigain Pünco Formation is composed of thick carbonate sequences with some clastic interbeds in Rongma (Nima, Tibet). A total of 13 carbonate microfacies were identified through thin-section microscopic analysis. According to the petrological characteristics and assemblage types, six sedimentary facies were recognized, i.e., detrital littoral, restricted-platform, open-platform, platform-edge bank, platform-edge reef, and slope facies. The results show that the Late Triassic Rongma was dominated by shallow-marine carbonate platform environment with local bathyal slope facies. During this period, four major transgression-regressive cycles may have occurred, together with several smaller sea-level fluctuations at intervals. Regionally, the sedimentary environment in the northern margin of the Bangong-Nujiang Ocean was similar to that in the Late Triassic, and the regional unconformity between the Upper Permian and Upper Triassic sequences was widely developed. Therefore, we considered that the Bangong-Nujiang Ocean was opened in an east-west quasi-simultaneous mode before the Late Triassic.

    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
    2022, 36(01):  58-67.  DOI: 10.19657/j.geoscience.1000-8527.2021.165
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    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.

    Sediment Transport Characteristics of Mountainous Rivers in Different Climatic Zones of Coastal China
    SUN Shuang, HU Ke, LI Yan, YANG Junpeng
    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.

    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
    2022, 36(01):  77-87.  DOI: 10.19657/j.geoscience.1000-8527.2021.166
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    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.

    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
    2022, 36(01):  88-95.  DOI: 10.19657/j.geoscience.1000-8527.2021.172
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    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.

    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
    2022, 36(01):  96-104.  DOI: 10.19657/j.geoscience.1000-8527.2021.163
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    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.

    Geomorphic Evolution and Sedimentary Response of Cretaceous Qingshuihe Formation in Moxizhuang-Yongjin Area, Junggar Basin
    ZHU Zhenjun, LI Qi, LI Jian, CHEN Hehe, HU Junjie, GENG Hui, DING Xiaojun, BAI Jinlian
    2022, 36(01):  105-117.  DOI: 10.19657/j.geoscience.1000-8527.2021.177
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    Sedimentary filling characteristics of the basin are different under different paleogeomorphic backgrounds. For the Lower Cretaceous Qingshuihe Formation (K1q) of Moxizhuang-Yongjin area (Junggar Basin), we studied the stratigraphy, sediment source and depositional system on the basis of paleogeomorphic evolution via integrated field outcrop, core logging, and 3-D seismic data analysis. The results show that K1q is a whole 3rd order sedimentary sequence: the 1st member can be classified into LST and TST, while the 2nd member is HST. In the Early Cretaceous, the Chepaizi-Mosuowan paleouplift was largely buried, and the local highs of the paleouplift were still exposed. As the whole basin was steadily deposited, the paleouplift gradually disappeared. During the LST period, the depositional center of the basin was located north of the study area. From the TST to HST period, the basin geomorphology was gentle and the depositional center moved southward gradually under tectonic uplift and tilting in the north. With tectonic evolution, the provenance system of the north basin was supplied to the study area from the northeast and northwest. In shallow water environment of the gentle slope of the basin, the far braided river delta and shallow lake depositional system was developed. During the LST period, due to the combined influence of paleouplift residual geomorphology, lake-level changes and hydrodynamic conditions, the sediments debris were mostly deposited in the low-potential geomorphologic area, whereas the shallow-water braided-river delta was locally developed. In the study area, the sediments were mainly deposited in the inner delta front, and underwater distributary channels were formed in succession. The sedimentary system developed in the LST period may have flattened the primitive geomorphology, and the shallow lake system was inherited in the TST period. The shallow water braided river delta sedimentary system was developed in the HST period. The HST period was dominated by the outer delta front deposition at Moxizhuang-Yongjin, widely developed sheet sand and locally developed underwater distributary channel. Inheritance geomorphology may have controlled the sedimentary accommodation in different parts of the basin, determined the sediment transport and dispersion path, and controlled the basinal sedimentary filling types and characteristics.

    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
    2022, 36(01):  118-129.  DOI: 10.19657/j.geoscience.1000-8527.2021.198
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    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.

    Geothermal Field Characteristics and Maturity History of Source Rocks in Baiyun Sag, Pearl River Estuary Basin
    HUANG Yuping, LONG Zulie, ZHU Junzhang, SHI Chuang, ZHANG Bo, ZHANG Xiaolong, CHEN Cong
    2022, 36(01):  130-139.  DOI: 10.19657/j.geoscience.1000-8527.2021.174
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    By correcting and analyzing the geothermal data (BHT, MDT and DST) from 108 wells in the Baiyun Sag, Pearl River Estuary Basing we reconstructed the current geothermal field of the sag from spots to planes. Combined with geological and geochemical data, we forward simulated and restored the thermal evolution and hydrocarbon generation history of source rocks in the sag. The results show that: (1)the Baiyun Sag shows characteristics of varying geothermal field, and the geothermal gradient is distributed in 35-60 ℃/km, decreasing from south to north; (2)Controlled by the varying geothermal fields in the Baiyun Sag, the source rock thermal history of different depressions in the sag is different. The Wenchang Formation source rocks in the main depression are highly mature to over mature, and those in the east, west and south depressions are mature to highly mature; (3)The high varying geothermal field in the Baiyun Sag likely leads to the evolution characteristics of high heat and rapid maturity of source rocks. With increasing geothermal gradient, the maturity threshold of source rocks quickly becomes shallow, and the hydrocarbon generation window becomes narrow; (4)Different depressions in the Baiyun Sag have different hydrocarbon generation characteristics: Kerogen oil and gas generation in the Wenchang Formation source rocks in the main depression was early. The oil generation occurred mainly before 23.03 Ma, and the gas generation occurred in 33.9-10.0 Ma; Source rocks in the east, west and south depressions are buried shallow, and the hydrocarbon generation there was relatively late (since 23.03 Ma). The oil and gas are cogenetic.

    Logging Identification Method of Low Porosity and Low Permeability Reservoir Effectiveness Based on Lithofacies Units and Pore Structures: An Example from NB1 Structure in Xihu Depression
    CUI Weiping, YANG Yuqing, LIU Jianxin
    2022, 36(01):  140-148.  DOI: 10.19657/j.geoscience.1000-8527.2021.144
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    The Xihu Sag in the East China Sea is one of the largest offshore basins. In recent years, major oil and gas discoveries have been made in the reservoirs of the mid-deep Huagang Formation. However, due to the large thickness, strong heterogeneity, low porosity and low permeability, and complex pore structure of the reservoir, it brings great difficulties to fine evaluation and prediction of sweet spots. This paper classified 6 types of micro-scale lithofacies units for the reservoirs in the study area based on the identification of lithology and bedding structure by using high-resolution electrical imaging data, namely trough cross bedding fine-medium sandstone, plate cross bedding fine-medium sandstone, trough cross bedding fine sandstone, plate cross bedding fine sandstone, massive bedding sandstone and calcareous cemented sandstone. And furthermore, NMR logging data was used to finely characterize the pore structure of different lithofacies units. The results show that the three lithofacies of trough cross bedding fine-medium sandstone, plate cross bedding fine-medium sandstone, and trough cross bedding fine sandstone have a drainage pressure less than 0.5 MPa and an average pore throat radius greater than 0.5 μm. The lithofacies of plate cross bedding fine sandstone has a displacement pressure between 0.5 MPa and 1.0 MPa, and an average pore throat radius between 0.25 μm and 0.5 μm. The above four types of lithofacies have coarser lithology, more developed cross bedding, lower displacement pressure, and larger average pore throat radius, which are favorable sweet spots in the study area. Based on the above studies, a classification scheme suitable for fine reservoir evaluation and sweet spots identification in the study area has been established, which provides a reliable basis for further exploration and development in the study area.

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

    Correlation of Clay Minerals and Gas Hydrate Saturation in Sediments from the Hydrate Ridge, Eastern Pacific Ocean
    SHANG Wei, SU Xin, BAI Chenyang, CUI Hongpeng
    2022, 36(01):  159-171.  DOI: 10.19657/j.geoscience.1000-8527.2021.175
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    To understand the correlation between clay minerals and gas hydrate saturation in hydrate reservoir strata, we analyzed the clay minerals in sediments from three drillholes (1245B, 1244C and 1251B) from the Ocean Drilling Program (ODP) Leg 204 on the Hydrate Ridge, Eastern Pacific Ocean. Montmorillonite, illite and chlorite are the main clay mineral components (average 40.3%, 33.4% and 21.4%, respectively), and kaolinite is minor (average 4.9%). The vertical distribution patterns of illite, chlorite and kaolinite are similar, opposite to that of montmorillonite. The data show positive correlation between hydrate saturation and montmorillonite content in the three holes, and the degree of positive correlation increases with depth, which is dominated by fine-grained sediments (R = 0.55 - 0.97). Meanwhile, gas hydrate saturation is negatively correlated with illite, chlorite and kaolinite. The differences of hydrate reservoir thickness and distribution patterns of hydrate saturation in the three holes suggest complex controlling factors for hydrate saturation, including mainly (1) gas-fluid supply and migration and (2) lithology. Correlation between montmorillonite content and hydrate saturation in the fine-sediment interval might belong to subordinate influence. In order to test any relationship between montmorillonite and hydrate saturation in other regions, we used the records from drillhole 17-07P in the Krishna-Godavari Basin (offshore India) for comparison with our data. Results indicate that the values of sand components in reservoir strata of this region are significantly higher than that on the Hydrate Ridge, showing a positive correlation between hydrate saturation and montmorillonite content in the sand reservoir strata. The comparison results indicate that the hydrate saturation controlling factors vary between two areas. In view of the difference between two types of correlation (i.e., between the montmorillonite content and hydrate saturation, and between the contents of illite, chlorite and kaolinite and hydrate saturation) in the fine-grained sediments, we inferred that montmorillonite is conducive to the hydrate formation due to its special layered crystal structure and surface chemical properties (negative charge and exchangeable hydrate cation in the interlayer surface), which benefits natural gas hydrate formation and accumulation. The properties of illite, chlorite and kaolinite are different from montmorillonite (weaker water absorption, and swelling and methane adsorption capacity than montmorillonite), and is inconducive to natural gas hydrate accumulation.

    Study on the Relationship Between Spectral Characteristics of Seismic Wave Field and Gas Content of Plume in Cold Seepage
    LIU Yilin, LI Canping, GOU Limin, WANG Hongtao, ZENG Xianjun, CHEN Fengying, GUO Zihao, TIAN Xinyu
    2022, 36(01):  172-181.  DOI: 10.19657/j.geoscience.1000-8527.2021.145
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    To study the seismic response characteristics of plume and inversion of gas content in plume, we used the single- and multi-channel seismic data in seismic migration profile of the actual plume to firstly analyze the time-domain seismic waveform characteristics and the seismic wave field spectral characteristics. The plume time-domain waveform shows scattering features and wide spectrum, showing the characteristics of scattering wave with more forks. Gas content was inversed through the existing relation model of gas content and amplitude attribute, and the plume seismic spectral parameters were extracted. Finally, the correlation between the plume seismic spectral parameters and gas content was analyzed. The results show that the gas content variation would change each of the spectral parameter, and all the spectral parameters (except dominant bandwidth) are positively correlated with the gas content, and the correlation curves of total energy and limited bandwidth energy have the best fitting. Distribution of the dominant frequency and the maximum amplitude spectrum is scattered, but the fitting results still show a positive correlation trend. Negative correlation is presented between the dominant bandwidth and the gas content. The time-domain waveform characteristics, seismic wave field spectral characteristics, and the relationship between seismic signal spectral parameters and plume gas content strengthens the foundation for seismic detection and gas content inversion of plume.

    Well Logging Evaluation for Three-Phase Zone with Gas Hydrate in the Shenhu Area, South China Sea
    XIE Yingfeng, LU Jing’an, KUANG Zenggui, KANG Dongju, WANG Tong, CAI Huimin
    2022, 36(01):  182-192.  DOI: 10.19657/j.geoscience.1000-8527.2021.167
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    During depressurization for the production test of natural gas hydrate, the free gas in the three-phase zone (gas hydrate, free gas, and water) was exploited first, which improves the depressurization efficiency and enhances the gas hydrate dissociation. Therefore, well-logging evaluation for three-phase zone with the core calibration logging method in Shenhu area (South China Sea) is important for the reserve calculation of gas hydrate bodies and subsequent industrial production. Compared with those in the gas hydrate layer, both the density and neutron porosity decrease, and the compressional wave speed drops dramatically in the three-phase zone. However, the shear modulus is still above the background and the chloridion concentration of core porewater falls below that in the free gas layer. Consequently, the three-phase zone can be identified. The density and hydrogen index of gas hydrate are close to those of water, thus the density and neutron porosity are only affected by the free gas, when the lithologies and physical properties are similar. We found that the reduction in density and neutron porosity are linearly correlated with core analysis gas saturation in the three-phase zone. Thus, for the gas saturation estimation, the dual-parameter binary linear regression model, which comprises the density and neutron porosity, was developed. Based on the water saturation and gas saturation achieved from the Indonesian formula and the dual-parameter free gas calculation model, respectively, the gas hydrate saturation was calcula-ted. The estimated gas hydrate saturation in the three-phase zone are in good agreement with the gas hydrate saturation derived from the chloridion content of core porewater, indicating that well-logging evaluation method for three-phase zone is reliable.

    Experimental Dynamic Monitoring of Gas Hydrate Formation: A New ERT Method and Its Effectiveness Analysis
    LIU Yang, CHEN Qiang, ZOU Changchun, ZHAO Jinhuan, PENG Cheng, SUN Jianye, LIU Changling, WU Caowei
    2022, 36(01):  193-201.  DOI: 10.19657/j.geoscience.1000-8527.2021.103
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    At present, on-site monitoring techniques suitable for determining spatial changes in hydrate formation and dissociation for resource exploitation is still imperfect. The new ERT array comprises two sets of parallel vertical electrodes, each with 24 electrodes. Through conducting physical simulation experiment, the new ERT method is used to monitor the hydrate formation process, and the application effectiveness of the dynamic monitoring method is analyzed. Based on statistical analysis of the physical simulation data, the standard deviation is below 5% for 92% of the data, which supports that the experimental device can obtain high-quality electrical data. Through the simulation experiment of high-resistivity medium, it is found that temperature and pressure changes have little influence on the ERT monitoring results. The imaging results show that the sediment resistivity saturated with 3.5% NaCl solution is about 1 Ω·m, which is basically equal to that calculated by the Archie’s formula. The applicability of ERT monitoring method is verified. The new ERT method effectively monitors the resistivity change in hydrate formation. The average resistivity increases from 0.95 to 1.95 Ω·m with the hydrate formation, and the “climbing effect” is observed. This supports that the approach is effective in hydrate monitoring, and facilitates dynamic monitoring of the spatial hydrate-saturation distribution. The results provide experimental and theoretical support for further research on hydrate formation and dissociation in sediments, and provide reference for the development of field hydrate monitoring technology.

    Quantitative Method for Selecting Marine Natural Gas Hydrate Production Test Targets
    HU Gaowei, WU Nengyou, LI Qi, BAI Chenyang, WAN Yizhao, HUANG Li, WANG Daigang, LI Yanlong, CHEN Qiang
    2022, 36(01):  202-211.  DOI: 10.19657/j.geoscience.1000-8527.2021.173
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    Prerequisites for hydrate production field test are whether the target meets the geological and engineering conditions for recoverability. However, since previous work is limited, there is no method to quantitatively evaluate the targets. To overcome the optimization problem of hydrate production test target wells, the comprehensive evaluation objective system is established from both geological and engineering perspectives. The six geological factors include porosity, hydrate thickness, hydrate saturation, intrinsic permeability, in-situ temperature and pressure; whilst the four engineering factors are water depth, underwater gradient, intensity and overlying layer thickness. The evaluation method (based on fuzzy comprehensive evaluation) is put forward to preliminary determine the comprehensive quantitative evaluation of production test target. Based on four typical hydrate coring sites (XX01, XX02, XX03 and XX04) in the Shenhu area of the northern South China Sea, the weights of the geological and engineering factors were estimated. The results show that the gas production potential at these four sites is unattractive. Nonetheless, site XX02 has the highest weight and was chosen as the target. The method of this study yielded good outcomes, and can provide support to optimize hydrate mining targets in intelligent quantification and promote hydrate industrialization in the future.

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

    Petrology
    Relation Between the Emeishan Mantle Plume Activity and Wumengshan Volcanic-Sedimentary Basin in Northeastern Yunnan
    ZHANG Honghui, WU Liang, LI Hong, YU Yangzhong, YUAN Yongsheng, ZHANG Liyuan, LI Shizhong, ZHAO Jianbo, PAN Jiangtao, ZHAN Huasi, SHI Haitao, CHEN Guiren
    2022, 36(01):  225-243.  DOI: 10.19657/j.geoscience.1000-8527.2021.070
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    To deepen the understanding on the evolution of the Emeishan mantle plume in Wumengshan area of northeastern Yunnan,detailed geological investigations of the Emeishan flood basalt and the underlying Qixia-Maokou Formation in the area, as well as petrological and isotopic chronological studies of the Emeishan flood basalt have been carried out. The results show that the crustal uplift caused by the Emeishan mantle plume activity formed the geological characteristics of the Qixia-Maokou Formation, which is thin in the west but thick in the east, and the Emeishan flood basalt, which is thick in the west but thin in the east, and the crustal uplift started at (273.1±3.1) Ma, and the uplift was about 512 m. However, this process was slow and did not cause the differential weathering and denudation of the limestone at the top of the Maokou Formation. Besides, the Emeishan flood basalt and Maokou Formation were basically deposited continuously. The Emeishan flood basalt in the Wumengshan area may have undergone four large-scale eruptions, corresponding to four sub-cycles. Each sub-cycle started with a sedimentary interbed, covered by a large number of overflow basalt facies. The eruption timing of the four subcycles was determined to be (261.9±2.0) Ma, (261.8±3.7) Ma, (261.6±1.9) Ma, (261.5±2.1) Ma, respectively. The main eruption phase lasted for about 0.4 My,and the mantle plume activity may last until (258.86±0.71) Ma. Based on the isotope chronology data, according to the thickness difference of Qixia-Maokou Formation, the horizontal and vertical variation characteristics of each subcycle of Emeishan flood basalt, the lithology and lithofacies characteristics of each subcycle and sedimentary interbed, the volcanic-sedimentary basinal evolution of Emeishan mantle plume in Wumengshan can be divided into the mantle plume upwelling (273.1-262.0 Ma), the basalt eruption(261.9-261.5 Ma ), and the mantle plume extinction stages (261.5-258.86 Ma ).

    Identification of Ophiolites in the Baimuxia-Mengangxia Area in the Eastern Part of the North Qilian Mountains and Their Regional Tectonic Significance
    LIU Jiandong, LI Wufu, WANG Guoliang, DONG Jinshen, CAO Jinshan, LI Honggang, ZHAO Zhongguo
    2022, 36(01):  244-258.  DOI: 10.19657/j.geoscience.1000-8527.2020.047
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    In order to strengthen the investigation of Early Paleozoic Archipelagic arc-basin-system ophiolitic mélange in North Qilian,the Baimuxia-Mengangxia ophiolite is selected for petrographic, chronological and geochemistry study.Baimuxia-Mengangxia ophiolite is located in Huzhu County, Haidong City, Qinghai Province,tectonically located in the middle-eastern section of the North Qilian orogenic belt.The ophiolite is mainly composed of peridotite,gabbro and basic volcanic rocks,making up a relatively complete ophiolite unit.Single zircon LA-ICP-MS U-Pb isotope dating of gabbro was carried out, and the weighted average age of 206Pb/238U was (525.2 ± 1.1) Ma (MSWD=0.06).It represents the age of ophiolite formation, corresponding to the Early Cambrian.Petrogeochemical studies show that: The basic volcanic rocks in the ophiolite belong to tholeiite series, showing the geochemical characteristics of oceanic island basalts; in basalts Th/Yb-Nb/Yb and TiO2/Yb-Nb/Yb tectonic discrimination diagrams, it shows that the formation environment of the ophiolite is not related to subduction.Through detailed field investigation and regional comparison, it is considered that the ophiolite represents the northern Qilian oceanic crust of the Early Paleozoic, and together with the ophiolites such as Yushigou-Chuancigou, it constitutes the Dabanshan-Yushigou ophiolite belt.

    Remote Sensing Identification of Marble in Mazha Tectonic Mélange of West Kunlun Orogen
    CHEN Haiyun, QI Rui, ZHANG Zhi
    2022, 36(01):  259-265.  DOI: 10.19657/j.geoscience.1000-8527.2021.037
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    In order to study the usage of remote sensing technology to identify tectonic mélanges, we took the Mazha tectonic mélange in the West Kunlun Orogen as an example. The marble in the mélange was analyzed for their spectral characteristics. The ETM+ image spectral inversion method was used to establish the linear relations between the measured spectrum and image spectrum. Assisted with enhanced transformation processing, the gray-scale distinction of different lithologies was expanded, the target information was highlighted and the image effect improved. Our work has also enhanced the utilization of measured spectrum and the accuracy of lithological information extraction. This method can be used to recognize the marble in Mazha tectonic mélange of the West Kunlun Orogen.

    Discovery of Late Triassic Adakitic Rocks at Nianzishan in the Central Great Xing’an Range and Its Geological Significance
    FU Anzong, YANG Wenpeng, LIU Yuan, ZHAO Handong, WANG Guipeng, SHI Guoming, LI jinming, DENG Changzhou
    2022, 36(01):  266-281.  DOI: 10.19657/j.geoscience.1000-8527.2021.066
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    Geochronology and geochemistry of the Early Mesozoic Nianzishan granites were studied to constrain the tectonic evolution in the Central Great Xing’an Range. The studied syenogranite and quartz monzonite samples show LA-ICP-MS zircon U-Pb ages of 225.6-228.9 Ma, indicating that they were both emplaced in the Late Triassic. Both rock types have similar adakitic geochemical, including high Al2O3 and Sr contents and Sr/Y and La/Yb ratios, low Y and Yb contents, HREE depletions and slightly negative Eu anomalies. However, the syenogranite has higher MgO, LREE, Cr, V, and Sr contents, and higher Sr/Y and K/Rb ratios than the quartz monzonite. Such differences are likely caused by their different petrogenesis: partial melting of thickened lower crust for the syenogranite and partial melting of a delaminated lower crust for the quartz monzonite. Combined with previous studies, we conclude that the Late Triassic Adakitic rocks at Nianzishan were formed in a compressional orogenic setting related to the collision of the Xing’an and Songnen blocks, which was overprinted by the south-dipping subduction of the Mongol-Okhotsk Ocean. The discovery of adakitic rocks by melting of delaminated lower crust indicates the potential for exploration of porphyry Cu-Mo deposits in the Nianzishan and adjacent area.

    Zircon U-Pb Geochronology, Hf isotope and Whole-Rock Geochemical Characteristics of Xiaohanshan Pluton in Haobugao Pb-Zn Deposit, Inner Mongolia
    ZHU Tong, SUN Zhenjun, YU Henan, WANG Chengyang, LIU Guanghu
    2022, 36(01):  282-294.  DOI: 10.19657/j.geoscience.1000-8527.2021.046
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    The Haobugao lead-zinc deposit is tectonically located in the southern part of the Great Xing’an Range, and is part of the Huanggangliang-Ganzhuermiao tectono-metallogenic belt. In this paper, detailed data on petrology, U-Pb geochronology, geochemistry and Hf isotopes were presented on the Xiaohanshan pluton of the Haobugao lead-zinc deposit. The results show that the main rock type of the Xiaohanshan pluton is monzogranite, which was formed in the Early Cretaceous (143.9±1.1 Ma). The rocks have high SiO2 (66.96%-68.05%) and alkali (Na2O+K2O=9.91%-10.09%), but low Al2O3 (15.69%-16.49%), CaO (1.22%-1.41%), and TFe2O3/MgO (average 8.29). The rocks belong to metaluminous to peraluminous granites with right-inclining REE distribution patterns and distinct negative Eu anomalies (0.33-0.41). The samples also show enrichments in large ion lithophilic elements (LILEs, e.g., Rb, K) and other incompatible elements (e.g., Th, U), whereas high field strength elements (HFSEs, e.g., Nb, P, Nb, Ta, Ti) are depleted, showing A2-type granite affinity. The rocks have initial 176Hf/177Hf values of 0.282,829-0.282,936(average 0.282,888) and εHf(t) of 4.4 to 8.4 (average 6.7), indicating that the Xiaohanshan pluton is mainly derived from partial melting of the middle and lower crust with minor mantle material input. It is considered that formation of the Xiaohanshan pluton was related to the post-collision extensional tectonics in the Early Cretaceous Paleo-Pacific subduction continental margin.

    Late Silurian to Early Devonian Tectonic Evolution of Beishanyang: Constraints from Geochronology and Geochemistry of Intrusive Rocks in Southern Baiyunshan Ophiolitic Mélange Belt, Inner Mongolia
    CHENG Xianyu, TIAN Jian, DUAN Xiaolong, ZHAO Zenan, REN Bangfang, ZHANG Yong
    2022, 36(01):  295-306.  DOI: 10.19657/j.geoscience.1000-8527.2021.069
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    Intermediate-felsic intrusive rocks occur mainly as dykes in the southern part of the Baiyunshan ophiolite mélange belt in the Beishan Orogen, Inner Mongolia. LA-ICP-MS zircon U-Pb dating and whole-rock geochemical analysis were performed to study the rock type, geochronology and tectonic setting of the dykes. Meanwhile, it provides chronological constraints for the timing of the Beishan ocean closure. The results show that the intermediate-felsic dykes have SiO2=58.38%-69.46%, K2O=0.74%-1.38%, Al2O3=15.54%-16.95%, and Na2O=4.15%-5.36%. The rocks are calc-alkaline quartz diorite and peraluminous tholeiitic granodiorite. Zircon U-Pb ages of the quartz diorite and granodiorite are (420.0±1.0) Ma and (404.6±2.6) Ma, respectively, suggesting the dykes were intruded in the Late Silurian-Early Devonian. The quartz diorite and granodiorite were likely derived from a continental-margin volcanic arc and syn-collisional setting. The clear LREE/HREE enrichments and high field strength element (HFSE, e.g., Ta and Nb) depletions are typical of island arc affinity, which shows the occurrence of island arc magmatism in the Late Silurian-Early Devonian led by oceanic crust subduction. With the progress of subduction, the Beishan ocean may have closed completely in the Late Silurian-Early Devonian to form syn-collisional granites in the study area. The collision time should be before (404.6±2.6) Ma.

    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
    2022, 36(01):  307-320.  DOI: 10.19657/j.geoscience.1000-8527.2021.068
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    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.

    Element Geochemistry and Vanadium Occurrence of the Dagoujing Black Shales, Inner Mongolia
    ZHANG Hongyu, SU Li, QIN Hong
    2022, 36(01):  321-332.  DOI: 10.19657/j.geoscience.1000-8527.2020.054
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    Systematic analysis of ICP-AES, ICP-MS, XRD and EDS was carried out in this paper to discuss the occurrence and distribution of vanadium as well as formation and preservation conditions of the Dagoujing vanadium deposit in Inner Mongolia. The study showed that P2O5 contents ranged from 0.81% to 6.14%, and this high phosphor value indicates the enrichment of P in the strata; LOI values ranged from 7.75% to 41.24%, and this high value indicated that mica and argillaceous cement content were high in samples. Vanadium values ranged from 1,015.2×10-6 to 4,162.0×10-6, and all the data were much higher than the average composition of the crust. The black shales were classified as normal sedimentary rocks based on the U/Th values; V/Cr, Ni/Co, δU, δCe, Ce/La and V/(V+Ni) values as well as transformation of most of Fe in black shales into pyrite indicated that the black shales in this region formed in a relatively dry, anoxic, H2S-rich, reducing and close basin condition. Vanadium element in samples mainly occurred in roscoelite, which was in very fine phosphorus shape with polytype 2M1 and formula K(V,Al,Mg)2 AlSi3O10(OH)2. Occurrence of abundant single or aggregate pyrite in rocks created a favorable condition for vanadium enrichment and preservation in black shales.

    Geochemistry
    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
    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.

    LA-MC-ICP-MS Zircon U-Pb Dating and Provenance Characteristic from Baoshuping Formation of Erlangping Group of the North Qinling
    OU Weicheng, LI Chengdong, ZHANG Yongqing, ZHAO Ligang, XU Teng, XU Yawen, SUN Xuanye
    2022, 36(01):  347-361.  DOI: 10.19657/j.geoscience.1000-8527.2022.01.31
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    The tectonic attributes and age of Erlangping Group in the North Qinling orogenic belt have been controversial,and Baoshuping Formation lacks chronological data.In order to further determine the age and tectonic setting of Baoshuping Formation,detrital zircon dating and provenance studies by LA-MC-ICP-MS were carried out. The results show that the plagioclase biotite quartzite (18P3TW2) and the diopside-bearing biotite actinolite plagioclase granulite (18P3TW3) from Baoshuping Formation have completely different zircon age spectrum characteristics,indicate that they belong to the strata of different ages. The detrital zircons age spectrum of 18P3TW2,which originates from the North Qinling micro-continental block and North China block,is multi-peaked but short of the data about Early Paleozoic magmatic arc. The youngest group of zircons range from 493 Ma to 972 Ma. The detrital zircons age spectrum of the 18P3TW3 is unimodal,and the main source of zircons is the Erlangping arc magmatic rocks,of while the youngest group of zircons is 420-440 Ma. With comprehensive analysis of field characteristics,age spectrum of zircons and provenance characteristics,the strata represented by 18P3TW2 was formed in the early stage of the basin without large-scale volcanic action,so it should not be attributed to Baoshuping Formation. Baoshuping Formation, represented by the 18P3TW3,was formed in the late period of the basin,the main sedimentary age is Ordovician-Silurian,and the latest strata may extend to Early Devonian. Combined with the regional geological background,Baoshuping Formation was formed in the tectonic environment of the back-arc extensional basin caused by the northward subduction of Shangdan Ocean in Early Paleozoic.

    Ore Deposits
    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
    2022, 36(01):  362-377.  DOI: 10.19657/j.geoscience.1000-8527.2022.01.32
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    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.

    Geological Characteristics and Genesis of the Xinjiazui Gold Deposit in Back-Longmenshan Orogenic Belt
    LIU Ji, YANG Ke, ZHANG Xiaoxing, KOU Shaolei, YANG Wei, WANG Zhanbin, TIAN Yuan
    2022, 36(01):  378-388.  DOI: 10.19657/j.geoscience.1000-8527.2022.01.33
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    The Xinjiazui gold deposit is located in the north-eastern section of Back-Longmenshan orogenic belt. This deposit (annual gold resources of about 960 kg) is newly discovered by the Xi’an Center of Mineral Resources Survey in 2020, and shows huge resource potential. Based on detailed study of outcrops, exploration trench, drillhole logging and microscope observation, it is found that the mineralization of primary ores in the Xinjiazui gold deposit is dominated by quartz-vein-type gold ore. In addition, gold is mainly hosted by pyrite, quartz and a small amount of polymetallic sulfides and occurs as fracture gold or gold inclusions. Combining with the crosscutting relationship of veins, the characteristics of mineral paragenetic association and typical ore fabric, mineralization of the Xinjiazui gold deposit can be divided into hydrothermal mineralization epoch and supergene oxidation epoch. The hydrothermal metallogenic epoch is the main ore event, and can be subdivided into three stages: Ⅰ.quartz-pyrite stage, Ⅱ.quartz-calcite-natural gold polymetallic sulfide stage, and Ⅲ.quartz-carbonate stage. Moreover, the Xinjiazui gold deposit is developed in Yanzibian-Huashigou brittle-ductile shear zone, the ore production is strictly controlled by the shear zone, and high-grade gold ore is developed only in the position with strong ductile deformation and brittle fracture. Therefore, the Xinjjiazui gold deposit is a brittle-ductile shear zone type gold deposit.