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    2022, Volume 29 Issue 2
    25 March 2022
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    Thermal regime and metallogenesis of collisional orogens
    ZHANG Hongrui, HOU Zengqian
    2022, 29(2): 1-13. 
    DOI: 10.13745/j.esf.sf.2021.10.36

    Abstract ( 396 )   HTML ( 56 )   PDF (5274KB) ( 631 )  

    Previous studies have shown that the thermal regime of continental collisional orogen has important controls on the shape, size, tectonic pattern, magmatism and metamorphism of collision zones. However, the relationship between the thermal regime and metallogenesis of continental collisional orogen is unclear. Here, we compared the Pyrenean, Alpine, Caledonian, Zagros-Iranian, Himalayan-Tibetan and Variscan orogens in terms of their thermal regimes and mineral deposits, focusing especially on the relationship between the thermal regime and ore-forming temperatures. We found three types of deposits in these continental collisional orogenic belts: basin brine (e.g., Mississippi Valley-type Pb-Zn deposits), metamorphic fluids (e.g., orogenic Au deposits) and magmatic hydrothermal (e.g., porphyry Cu-Mo-Au deposits and greisen W-Sn deposits) deposits. Among them, the Mississippi Valley-type Pb-Zn deposits and orogenic Au deposits can occur in all types of collisional orogens. The ore-forming temperatures in these deposits are relatively high in hot collisional orogen and low in cold collisional orogen. However, magmatic hydrothermal deposits only occur in hot collisional orogens as the pressure-temperature conditions for hot collisional orogen overlap largely with that for wet granite solidus in the p-T diagram. The thermal structure of collisional orogens is affected easily by thermal disturbance conducive to crustal partial melting and forming ore-bearing magmas.

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    Deep seismic reflection profile reveals the deep process of continent-continent collision on the Tibetan Plateau
    GAO Rui, ZHOU Hui, LU Zhanwu, GUO Xiaoyu, LI Wenhui, WANG Haiyan, LI Hongqiang, XIONG Xiaosong, HUANG Xingfu, XU Xiao
    2022, 29(2): 14-27. 
    DOI: 10.13745/j.esf.sf.2021.7.13

    Abstract ( 564 )   HTML ( 55 )   PDF (13493KB) ( 687 )  

    The collision between the Indian and Asian plates uplifted the Himalayan-Tibetan Plateau, thickening and expanding the crust. The deep structure of the plateau-a scientific mystery of global concern-can reveal how the two continents collide and how the collision deforms the continent. One of the most effective ways to unlock this scientific mystery is deep seismic reflection profiling. For more than 20 years using this technology we have detected the fine structure of the thick crust of the Tibetan Plateau, overcoming the technical bottleneck of accessing the lower crust and the Moho and revealing the intracontinental collision process. Based on the research results, this paper systematically summarizes the deep behavior of the collision and subduction between the Indian and Asian plates under the Tibetan Plateau, on topics ranging from the NS-EW correlation to the plateau’s hinterland. The deep behavior includes the underthrusting of the Indian crust beneath the Himalayan orogenic belt on the southern margin of the plateau, the subduction of the lithosphere of the Alashan block in the Asian plate under the Qilian mountain in the northern rim of the plateau, the outward crustal extension in the Qilian mountain range, and the face-to-face collision between the Tarim block and the West Kunlun in the northwestern margin of the plateau; in the eastern margin of the plateau it was discovered that the Longriba fault, not the Longmenshan fault, is the western border fault of the Yangtze plate. In the plateau’s hinterland the Moho lines are thin and flat and lithosphere extension collapses. Multiple deep reflection profiles reveal the collisional behavior of the Indian and Asian plates under the Yalungzangbo suture zone. The subduction of the Indian continental crust varies from east to west, and the crust travels northward to different locations inside the Lhasa terrain. In the central suture zone, the upper and lower parts of the Indian crust become detached as the upper crust overthrusts while the lower crust subducts northward. During the subduction, material return and structural superposition cause the thinning and thickening of the Indian and Himalayan crust, respectively. The leading edge of the subducting Indian crust collides with the Asian crust and sinks into the mantle, while a near-vertical collision occurs between the Gangdise at the leading edge of the Asian plate, and the Tethys. Together, the partial melting of the lower crust of the Gangdise, the seismic data that show near transparent weak reflection and localized bright spot reflection, and the near-flat Moho, all reflect the extensional tectonic environment of the southern margin of the Asian plate.

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    Distinctive spatial-temporal evolution of Late Paleozoic to Mesozoic magmatic systems in Northeast Asia: Evidences for identification of the extent and superposition of multiple plate tectonic regimes
    WANG Tao, ZHANG Jianjun, LI Shan, TONG Ying, GUO Lei, ZHANG Xiaowei, HUANG He, ZHANG Lei, XUE Huaimin
    2022, 29(2): 28-44. 
    DOI: 10.13745/j.esf.sf.2022.2.5

    Abstract ( 400 )   HTML ( 22 )   PDF (11591KB) ( 408 )  

    The tectonic evolution of Northeast Asia has experienced the collision and post-collision processes of the Paleo-Asian Ocean, the Mongol-Okhotsk Ocean and the Paleo-Pacific Ocean. However, the spatial-temporal distribution ranges and overlapping processes of these three tectonic regimes have long been difficult to constrain properly. In this paper, we analyzed the spatial-temporal migration patterns of Late Paleozoic-Mesozoic magmatic rocks of Northeast Asia through the constructions of U-Pb age data of giant magmatic belts and a series of data-driven digital maps, with the aim to constrain the tectonic superimposition of the three tectonic regimes. We determined that the extent of each tectonic domain varies in different periods. During the Permian to Jurassic, Paleo-Asian Ocean experienced subduction and collision, which affected mainly the Alxa-northern margin of North China Craton-Da Hinggan Mountains areas; while the Okhotsk Ocean was mainly a continental margin environment, and its influence was initially limited to the central and northern Mongolia and areas around Baikal and then gradually extended to the Mongol-Okhotsk main suture zone in the Jurassic. In the Cretaceous, the Okhotsk Ocean orogenic belt extended and collapsed, which further expanded its influence, with its long-range effect reaching the areas affected by the Paleo-Asian Ocean. Meanwhile, the Paleo-Pacific tectonic system mainly developed in the Triassic to Jurassic, and its plate subduction reached the Da Hinggan-Taihang Mountains area-a gravity gradient zone in the eastern Asian continent, with its long range effect subsequently reaching the easternmost margin of the eastern Asian continent due to the subducting plate retreating during the Cretaceous. Thus, these processes of were superimposed on the products of the Paleo-Asian Oceanic system, together with these of the Mongol-Okhotsk Oceanic system, they all superimposed mainly on the Da Hinggan Mountains region.

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    Formation age of the Gaofan Group in Wutai area: New evidence from SHRIMP U-Pb zircon dating
    WAN Yusheng, DONG Chunyan, LI Pengchuan, MIAO Peisen, WANG Huichu, LI Jianrong
    2022, 29(2): 45-55. 
    DOI: 10.13745/j.esf.sf.2022.2.6

    Abstract ( 227 )   HTML ( 8 )   PDF (23127KB) ( 318 )  

    The Gaofan Group in Wutai area is of great significance for the sequence establishment of Early Precambrian metamorphic strata in the North China Craton. This paper carried out the geochemical analysis and SHRIMP U-Pb zircon dating of the Mohe Formation of the Gaofan Group. The metamorphic sedimentary rocks have a total REE (rare earth elements) content of (132.78-231.84)×10-6 (except for sample W1927, which has a total REE of 1016.55×10-6), with weak enrichment of LREE (light REE) relative to HREE (heavy REE) ((La/Yb)N between 4.5-12.5) and obvious negative Eu anomaly (δEu between 0.37-0.62), and are similar in REE composition to post-Archean argillaceous rocks. A muscovite-quartz schist sample (D004) has a large number of detrital zircons aged around 2.7 Ga, 2.5 Ga, 2.54 Ga, 2.3 Ga and 2.18 Ga, with the youngest grains derived probably from contemporary volcanic rocks. A pyrite-bearing muscovite schist sample (W1927) has the youngest zircon age of 2194 Ma, which is considered to represent the deposition time of the rock. Combined with previous studies, it is concluded that the formation age of the Gaofan Group can be constrained between less than 2176 Ma and 2350 Ma, and the detrital materials are mainly derived from Neoarchean-Paleoproterozoic metamorphic basement in Hengshan, Wutai, Fuping, Yunzhongshan, Luliang areas or further afield.

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    Deformation in subduction-accretionary complex belts: Characteristics, mechanism and differentiation from late-stage event
    ZHANG Jin, QU Junfeng, ZHAO Heng, ZHANG Beihang, LIU Jianfeng, ZHENG Rongguo, YANG Yaqi, NIU Pengfei, HUI Jie, ZHAO Shuo, ZHANG Yiping
    2022, 29(2): 56-78. 
    DOI: 10.13745/j.esf.sf.2022.2.4

    Abstract ( 454 )   HTML ( 18 )   PDF (21332KB) ( 413 )  

    Subduction-accretionary complex belts are an important component of orogenic belts and have great research values. They record the evolutionary history from the subduction to the collision periods as well as the history of intracontinental evolution after the collision event. Because the formation process of accretionary wedges is complex, and the deformation occurred during the subduction can undergo strong transformation due to the late-stage collision and intracontinental deformation, it is very important to distinguish between the initial and late-stage deformation, although such a task is very difficult. The subduction-accretionary complexes developed in China have all experienced significant late-stage transformations; therefore, the need for reasonable differentiation criteria for deformation of different stages becomes increasingly important in the study of orogenic belts of China continent. Based on the detailed descriptions of subduction-related deformation and its formation mechanism, this study comprehensively compares the similarities and differences in deformations formed in the subduction, collision and subsequent intraplate orogenic stages in terms of their distribution and development characteristics as well as the formation conditions and mechanisms of different structural elements, and puts forward the main principles for distinguishing deformations of different stages. Compared to the collision-induced deformation, deformation in the subduction stage is mainly concentrated in the subduction channels as simple shear or general shear primarily (thrust faults are common), with underplating and duplexing as the important features of deformation. The collision-induced deformation is diffused in matrix during the subduction, with faults, foliations and folds exhibiting dominant structural polarity; but regional-scale large folds are lacking. Pure shear deformation is rare and mainly developed in accretionary wedges above subduction channels. Abundant fluids and strong water-rock interaction directly control the deformation behavior, causing development of strain partitioning, from micro to regional scales. The collision stage mainly occurs in onshore environments, and the main deformation is concentrated near the contact zones between different geological units and large faults or shear zones. The structural polarity of faults and foliations is not obvious, and accretionary wedges are deformed as a whole, resulting in the development of large folds on a regional scale. Although fluids also exist during the deformation, their effects are not as obvious and strong as in the subduction stage, and thrust and strike slip faults are more common. However, many deformation indicators and differentiation criteria are not unique within a given environment; therefore, in practice, it is necessary to consider all aspects of such information so that reasonable judgment can be made.

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    Progress in geological study of oceanic plates
    LIU Yong, LI Tingdong, XIAO Qinghui, ZHANG Kexin, ZHU Xiaohui, DING Xiaozhong
    2022, 29(2): 79-93. 
    DOI: 10.13745/j.esf.sf.2022.2.7

    Abstract ( 381 )   HTML ( 16 )   PDF (14620KB) ( 419 )  

    The ages and types of orogenic belts in China vary greatly, where subduction accretionary complexes and ophiolite suites of various styles are developed through complex and changeable ocean-continent transition processes. How to study the orogenic processes such as ocean basin evolution and ocean-continent evolution has always been an intractable issue. To this end, the Regional Geology of China compilation project team has proposed the geological study of oceanic plate in an attempt to systematically study the geological construction and the structure of oceanic lithospheric plates such as orogenic subduction accretionary complex zone and ophiolite belt, and subsequently reconstruct the whole geological process from plate formation in the mid-ocean ridge to plate subduction in trench to eventual transformation of oceanic plate into land. This paper introduces the main research progress on the geology of oceanic plate focusing on the following four aspects. First, a preliminary geological framework of oceanic plate has been established. According to this model, the geological study of oceanic plate mainly concerns with the material composition of subduction-accretion complex, ophiolite type and its tectonic environment, unique sedimentary assemblages in oceanic plate and their characterization, paleoorogenic OPS sequence reconstruction, forearc volcanic assemblage in subduction zone, ocean-continent transition process and mechanism, and mineral formation and evolution in ocean-continent transition zone. Second, 62 subduction-accretion complex belts are identified, which include Beishan Niuquanzi-Mazongshan, Jiayin-Yilan, Chencai, East Kunlun Buqingshan-Animaqing, Yingyangguan, Dahongshan, Ganzi-Litang, and Xinyu Shenshan-Xingan Shenzhengqiao subduction-accretion complex belts, and so on. Subduction-accretion complex is the key to understanding the spatial-temporal structure, composition, and evolution of orogenic system. Third, intra-oceanic arc volcanic assemblages have been discovered in Qilian, which provides a petrological basis for the study of ocean-continent transition process. The Qilian orogenic belt is a classic area for studying the geology of oceanic plates. The study shows that a complete set of intra-ocean arc rock assemblages are exposed in Dangjinshan area. These rocks record the whole process of intra-ocean arc development from initial subduction to mature subduction in the study area. On this basis, the tectonic evolutionary history of Early Paleozoic in southern Qilian and northern Qaidam has been reconstructed, which provides a new basis for discussing the tectonic evolution of the Proto-Tethys Ocean in the Qilian orogenic belt. Fourth, the compilation scheme of the geological structure map of the oceanic plate is formulated. The compilation content contains five main categories: subduction-accretion complex zone; magmatic arc properties and attributes; high - ultra high pressure zone; deformation structural elements in subduction and collision periods; and tectonic evolution. The mapping unit is divided into three levels: accretionary complex (1st level), rock slice (2nd level), and matrix and rock block levels (3rd level). During the mapping process, it is necessary to clarify the nature and attributes of the magmatic arc as well as to clarify which ophiolite mélange (including subduction-accretion complex) or ocean is matched by a magmatic arc on the map. The structural element expression on the map focuses on distinguishing subduction and collision stages. The structural deformation traces in subduction and collision periods are identified by studying the temporal, phase and position states of structural deformation. Based on these preliminary research results, the project team in the next step will discuss composite evolution of the oceans in China and its constraint on continental evolution. In addition, the next research direction is to explore fundamental geological issues such as the Tethys Ocean, and the relationship between the Paleo-Pacific/Pacific transformation in eastern China and Mesozoic-Cenozoic mineralization. At present, the geological study of oceanic plates is still in its infancy. Major geological problems such as the genetic relationship between ocean plate geology and mineralization need in-depth study in the future.

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    Research progress on the subduction-accretion complex: Reconstruction of the tectonic framework of the Great Xing’an Range
    YANG Xiaoping, ZHONG Hui, YANG Yajun, JIANG Bing, QIAN Cheng, MA Yongfei, ZHANG Chao
    2022, 29(2): 94-114. 
    DOI: 10.13745/j.esf.sf.2022.2.10

    Abstract ( 224 )   HTML ( 10 )   PDF (11578KB) ( 331 )  

    The Great Xing’an Range region, which experienced the closure of the Paleo-Asian Ocean during the Paleozoic, has developed numerous arc-basin systems and ophiolite belts. In this contribution, based on the concept of “ocean plate geology”, various tectonic units including subduction-accretion complexes, ancient block relicts, island arcs, forearc basins and back-arc basins were identified based on 1: 1 000 000 scale geological mapping and geological survey of the region. Among the tectonic units, there are 9 subduction-accretion complex belts, of which 3 were identified for the first time. The subduction-accretion complex belts, structurally equivalent to 5 suture zones, divide the tectonic blocks and magmatic arcs of the region. These suture zones mainly orient in the northeast direction, and their formation age becomes younger southward, from Early Ordovician to Middle and Late Permian, indicating the subduction initiates in the northern Erguna region then retreats southward in a prolonged subduction-accretion process. Plenty of new continental crust are formed, followed by southward accretion. Not until the Early to Middle Triassic, the Central Asian Orogenic Belt and North China Craton are amalgamated along the Xar Moron suture zone. By reconstructing the Paleozoic tectonic framework of the Great Xing’an Range region, this study helps to advance our understanding of the oceanic-continental transition in the eastern Paleo-Asian Ocean.

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    Spatio-temporal distribution of Mesozoic volcanic strata in the Great Xing’an Range: Response to the subduction of the Mongol-Okhotsk Ocean and Paleo-Pacific Ocean
    YANG Yajun, YANG Xiaoping, JIANG Bing, WANG Yan, PANG Xuejiao
    2022, 29(2): 115-131. 
    DOI: 10.13745/j.esf.sf.2022.2.11

    Abstract ( 235 )   HTML ( 10 )   PDF (8708KB) ( 231 )  

    To improve the regional comparability of Mesozoic volcanic rock strata in the Great Xing’an Range region, we examined in-depth the tectonic relationship between the volcanic rock strata and the Paleo-Pacific/Mongol-Okhotsk Plates. By mapping (1: 1 million) the Great Xing’an Range region, combined with data on rock association, paleontology, contact relationship and regional comparison, as well as the latest zircon chronology (through U-Pb,40Ar/39Ar zircon dating), we redefined the Mesozoic volcanic strata of the Great Xing’an Range region, and subsequently further defined the formation periods of the Tamulangou (172-161 Ma), Manketouebo (162-148 Ma), Manitu (158-145 Ma), Baiyingaolao (145-129 Ma), Meiletu (143-128 Ma), Longjiang (128-121 Ma), Guanghua (128-118 Ma), Ganhe (120-113 Ma) and Gushanzhen (118-110 Ma) Formations. Together with the spatial distribution analysis of volcanic strata, taking into account the subduction of the Paleo-Pacific and Mongol-Okhotsk Plates at the continental margin of East Asia, the tectonic setting of the Mesozoic volcanic rock strata was analyzed. We found that the NE-trending volcanic rock strata of the Middle-Late Jurassic mainly formed in the extensional tectonic setting associated with the southward subduction of the Mongol-Okhotsk Plate, while the NNE-trending volcanic rock strata of the Early Cretaceous mainly formed in the extensional tectonic setting associated with the subduction of the Izenaki Plate beneath the East Asian continent. The molasse-like deposits in the Kaikukang and Murui Formations, developed between the Late Jurassic-Early Cretaceous volcanic strata, are the main sedimentary record of the transition stage between the two tectonic domains.

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    Late Triassic magmatic activity in Duobaoshan area, Heilongjiang Province: Response to the southward subduction of the Mongol-Okhotsk Ocean
    LIU Baoshan, CHENG Zhaoxun, KOU Linlin, DENG Changzhou, YANG Xiaoping, ZHANG Chunpeng, LI Chenglu, HAN Renping
    2022, 29(2): 132-145. 
    DOI: 10.13745/j.esf.sf.2021.7.15

    Abstract ( 155 )   HTML ( 7 )   PDF (7674KB) ( 156 )  

    Late-Triassic magmatic rocks have been discovered in recent years in the Duobaoshan area of Nenjiang. So far, the tectonic setting, genesis and metallogeny of the magmatic activity have not been well understood, which significantly hindered our understanding of the regional tectonic evolution and prospecting for polymetallic deposits in this area. In this paper, we conducted systematic petrological, geochemical and geochronological studies of tonalite in the Duobaoshan deposit and diorite in the Zhengguang deposit. LA-ICP-MS zircon U-Pb dating yielded an age of (226.3±2.3) Ma for the Duobaoshan tonalite and (229.3±3.1) Ma for the Zhengguang diorite, indicating the two minerals, with similar formation age, are probably derived from the same magma chamber. The tonalite had elevated SiO2 (64.25%-66.44%), Al2O3 (16.54%-17.21%), (K2O+Na2O) (8.15%-8.50%) and low CaO (2.27%-2.95%), MgO (0.99%-1.16%), TiO2 (0.31%-0.36%) and P5O2 (0.16%-0.17%) contents comparable with the diorite whose major element contents were SiO2 (57.12%-58.5%), Al2O3 (14.59%-15.26%), Na2O+K2O (5.34%-6.16%), TiO2 (0.83%-0.97%), and P2O5 (0.15%-0.27%), with similar FeO/MgO (1.12-1.25) ratio. The Duobaoshan tonalite is characterized by depletions of Rb, Nb, and Sm, enrichments of Ba, U, Zr and Sr, and obvious positive Eu anomaly (δEu, 1.21-1.57). The Zhengguang diorite is characterized by depletion of Rb, Nb and Sm, enrichment of Ba, Th, Sr, Hf, and weak positive Eu anomaly (δEu, 0.93-1.22). Both tonalite and diorite are rich in light rare earth elements (LREE) and depleted in heavy rare earth elements (HREE), and have similar curve pattern on REE or trace element diagrams suggesting a common magmatic source. The magma probably derived from the partial melting of the mantle wedge metasomatized by the subduction fluid dehydrated from the downward moving Mongol-Okhotsk plate. The confirmation of the calc-alkaline magmatism in the Duobaoshan district indicates the subduction of the Mongol-Okhotsk oceanic plate can have remote influence, reaching as far as the eastern margin of the Xing’an Block. By compiling the metallogenic ages and background of the Late Triassic deposits in the study area, we can show that the Late Triassic magmatic activity in Duobaoshan area has great Ag-Cu-Mo mineralization ability and the study area has high exploration potential.

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    Composition of the Fukeshan magmatic arc in the northern Great Xing’an Range: Constraints on the southward subduction of the Mongol-Okhotsk oceanic plate
    LI Wenlong, YANG Xiaoping, QIAN Cheng, LI Chenglu, LÜ Mingqi, CHENG Zhaoxun, WANG Lijia
    2022, 29(2): 146-163. 
    DOI: 10.13745/j.esf.sf.2021.7.14

    Abstract ( 156 )   HTML ( 12 )   PDF (9113KB) ( 156 )  

    The Fukeshan magmatic arc extends north-east in Fukeshan-Gulianhe area, northern Great Xing’an Range. Its material composition, formation age and spatial distribution pattern are very important for studying the Late Triassic tectonic evolution of the Mongol-Okhotsk ocean. In this paper, the petrology, geochemistry and zircon U-Pb dating of gabbro, diorite and granodiorite from the Fukeshan magmatic arc are reported, aiming to furthering our understanding of the tectonic setting of the northern Great Xing’an Range during the Late Triassic. LA-ICP-MS zircon U-Pb dating yielded the crystallization ages of (205.7±2.2) Ma and (203.2±2.5) Ma for gabbro and granodiorite, respectively, which correspond to the tectonic-magmatic event in the Late Triassic. Petrological and geochemical study indicate that the gabbro and diorite belong to tholeiite and calc-alkaline transition series rocks with high Na, Al, Ca, Mg and Mg# contents and low Ti contents. They are enriched in large ion lithophile elements (LIFE) and light rare earth elements (LREE). The granodiorite belongs to calc-alkaline transition series rocks with high Si, Na and Al contents and low Mg contents. The rock has low content of Y and Yb, with no obvious negative Eu anomaly and belongs to O-type adakite. The Fukeshan magmatic arc has a distribution pattern from north to south, and the corresponding lithologic variation indicates the Mongol-Okhotsk ocean has a polarity of southward subduction.

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    Late-Paleoanthics diabase from the eastern part of the Bangong Lake-Nujiang subduction belt: U-Pb geochronology, Hf isotopic composition and geological characteristics
    REN Fei, YIN Fuguang, PENG Zhimin, PAN Guitang, WEI Dong
    2022, 29(2): 164-179. 
    DOI: 10.13745/j.esf.sf.2021.7.27

    Abstract ( 248 )   HTML ( 9 )   PDF (14185KB) ( 218 )  

    The Jiayuqiao-Tongka mélanges are located within the eastern part of the Bangong Lake-Nujiang subduction-accretion complex belt from Jiayuqiao to Bangda area whose spatial distribution, material composition, tectonic setting and genesis have been discussed to some extent by previous researchers but have not been studied in detail. For example, the formation era of the subduction-accretion complex has been determined to be the Late Paleozoic by geological survey (1: 250000) but lacked precise geochronological and geochemical constraints. In this contribution, the diabase of the Bangda Formation is investigated through detailed petrographic, geochemical and chronologic analyses to shed light on the development time and tectonic setting of the Bangong Lake-Nujiang structural zone. The diabase was found to be enriched in LILEs (Rb, Ba) and depleted in high HFSEs (Nb, Zr) and exhibited the geochemical characteristics of N-MORB. Its LREE pattern indicated a depleted N-MORB mantle source, while geochemical analysis further suggested the diabase is sourced from 30% partial melting of spinel lherzolite formed in a back-arc rift basin. The LA-ICP-MS U-Pb dating of zircon from the diabase yielded an average zircon age of (330.9 ± 1.6) Ma, which represents the crystallization age of diabase, indicating the Bangda diabase is formed in the Early Carboniferous epoch, and supporting the notion that the Bangong Lake-Nujiang structural zone retains geological information of the residual Paleo-Tethys. The results of this study on the Early Carboniferous N-MORB diabase provided an important reference for the reconstruction of the regional tectonic setting as well as for future studies on the spatio-temporal evolution of the Paleo-Tethys in the Bangong Lake-Nujiang region.

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    Geological characteristics and tectonic background of the Mesoproterozoic ophiolite mélange in central and southern Yunnan
    ZHANG Liang, ZHANG Heng, GONG Chengqiang, DING Xiaozhong, ZHANG Chuanheng, LIU Yong, GAO Linzhi, LIU Yanxue
    2022, 29(2): 180-197. 
    DOI: 10.13745/j.esf.sf.2021.7.16

    Abstract ( 201 )   HTML ( 8 )   PDF (14023KB) ( 161 )  

    Outcrops of ophiolitic mélange are found in the Cuoke Dazhai area of Yuanjiang County. The Cuoke ophiolitic mélange has undergone metamorphism and deformation due to late tectonism. The lithology of the ophiolitic mélange is complex and fault contact exists between the block and matrix. The bedrock is mainly composed of siliceous rock, fused tuff and granitic conglomerate. The main types of rock blocks are pyroxenite, gabbro, diabase, basalt, granite, etc. The zircon SHRIMP U-Pb age for tuff in the Cuoke ophiolitic mélange was (1170±7) Ma (MSWD=0.54, n=12); for granite conglomerate matrix (a single age) (1151±5) Ma (MSWD=1.3, n=17), gabbro block (1168±8) Ma (MSWD=0.72, n=17), plagiogranite block (1163±9) Ma (MSWD=1.83, n=15), and granite porphyry block (1186±6) Ma (MSWD=0.92, n=17). These ages indicate the ophiolitic mélange is formed in the Late Mesoproterozoic. The chondrite-normalized REE patterns for gabbro of the Cuoke ophiolitic mélange showed a relatively flat right dipping trend similar to that of E-MORB. In the MORB standardized diagram, no obvious negative NB-TA anomalies were observed. The extremely low average Zr/Nb (8.65), La/Nb (1.05), Ba/Nb (10.72), Th/Nb (0.10), Th/La (0.09), Ba/La (10.56) ratios, extremely low Zr/Hf (43.4) ratio, along with the observation that trace element discrimination points mainly fell inside or near the range of intraplate basalt, suggest the Cuoke ophiolite belongs to MOR-type ophiolite and may be formed in a tectonic environment of plate extension. The εHf(t) values for zircon from fused tuff ranged, all negative, from -8.7 to -4.7, or averaged at -6.6. The Hf isotopic model age ( t D M C) was 2534-2296 Ma, averaging at 2408 Ma, indicating the tuff is derived from the remelting of the Paleoproterozoic crystalline basement. Characterization of the Cuoke ophiolitic mélange is of great significance for recognizing the attributes of the Laochanghe Formation of the Dahongshan Group and for understanding the Mesozoic and Neoproterozoic magmatic and tectonic events in the southwestern margin of the Yangtze block, as well as for delineating the tectonic units of the basement of the Yangtze block.

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    Detailed upper crustal velocity structure beneath the Qinling Orogen and adjacent region
    LI Wenhui, WANG Haiyan, GAO Rui, LU Zhanwu, LI Hongqiang, HOU Hesheng, XIONG Xiaosong, YE Zhuo
    2022, 29(2): 198-209. 
    DOI: 10.13745/j.esf.sf.2021.7.9

    Abstract ( 248 )   HTML ( 13 )   PDF (8717KB) ( 368 )  

    The geologic framework of the Qinling Orogen and adjacent region is developed as a result of the convergence of the North China Craton and Yangtze Craton during a long and complex evolutionary history. Detailed upper crustal structure connecting the superposed surface geological phenomena with geophysical images is a key for understanding the geodynamics of the convergence process. The Qinling wide angle reflection and refraction seismic profile extends from the Ordos basin, across the Weihe graben, Qinling orogeny, Dabashan thrusting nappe, to the Sichuan basin. The seismic waves from 15 explosions were recorded on 281 DFZ recorders, of which 690 arrivals of refracted waves from sediments and basement (Pg) were typically picked, and finite-difference tomography algorithm was used to obtain the upper crustal velocity structure. After 20 iteration, the RMSD for the resulting arrival time was 0.105 s, with good convergence. The final P-wave velocity model contains the following features of tectonic significance: (1) The Weihe graben is a typical down-faulted basin with the deepest sediments, as deep as 7 m, in the south, and its formation is controlled by the Qinling northern border fault, Weihe fault and Qianxian-Fuping fault. (2) The upper crustal structure of the Qinling orogen varies significantly with generally high velocity. (3) Sediments of 3-6 km thick beneath the Dabashan Mountain are preserved, but the velocity structure is not uniform, which reflects the thrusting induced reformation.

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    Crustal-scale duplexing beneath the Yarlung Zangbo suture in the western Himalaya
    LU Zhanwu, GAO Rui, Simon KLEMPERER, WANG Haiyan, DONG Shuwen, LI Wenhui, LI Hongqiang
    2022, 29(2): 210-217. 
    DOI: 10.13745/j.esf.sf.2021.7.10

    Abstract ( 296 )   HTML ( 20 )   PDF (4925KB) ( 244 )  

    The fate of the Indian plate during continental collision with Asian terranes, and the proportion of the Indian crust that is underthrust or subducted beneath Tibet as opposed to transferred to the upper (Himalayan) plate, are much debated. The active geometry of low-angle underthrusting or subduction of the Indian plate beneath the Lesser and Greater Himalayan thrust sheets is well known from seismic imaging. Previously, only images with lower resolution have been obtained in the Main Himalayan Thrust beneath the Yarlung Zangbo suture that separates Indian and Asian rocks at the surface. It remains controversial whether the orogenic wedge between the Main Himalayan Thrust and the Yarlung Zangbo suture, formed of Indian crust transferred to the upper plate, is evolving by thrust-faulting in a critical-taper wedge or by southward extrusion of a ductile channel flow. Here we present a seismic reflection profile across the western Himalaya at 81.5°E, and show that the Main Himalayan Thrust dips 20 to 60 km depth beneath the Yarlung Zangbo suture, approaching a continuous Moho reflection at 70-75 km depth. The Indian crust being transported northwards beyond the Yarlung Zangbo suture is no more than 15 km thick, reduced from its original 40 km thickness by transfer of material from the lower plate to the upper plate through crustal-scale duplexing.

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    Geochronology and geochemistry of 830 Ma gabbro in the western segment of the Jiangnan Orogen and constraint on its petrogenesis
    KOU Caihua, LIU Yanxue, LI Jiang, LI Tingdong, DING Xiaozhong, LIU Yong, JIN Shengkai
    2022, 29(2): 218-233. 
    DOI: 10.13745/j.esf.sf.2021.7.11

    Abstract ( 190 )   HTML ( 7 )   PDF (11857KB) ( 138 )  

    We report gabbro discovered in the western segment of the Jiangnan Orogen Belt, Sibao area, northern Guangxi Province. The gabbro contains mostly plagioclase and clinopyroxene and a small amount of olivine and Fe-Ti oxide minerals, indicating likely fractionation of plagioclase, clinopyroxene and some olivine within the magma chamber. The gabbro specimen has a zircon SIMS U-Pb age of (830±7) Ma, suggesting gabbro emplacement at ~830 Ma. The bulk-rock is characterized by relatively low SiO2 (48.46%-53.99%) and high MgO (9.27%-25.22%) contents with Mg# of 62-79. It belongs to typical calc-alkalic arc rock, characterized by enrichments of light rare earth elements and large-ion lithophile elements relative to heavy rare earth elements ((La/Yb)N=2.2-3.7, (La/Sm)N=2.5-2.9), significantly negative Nb, Ta and Ti anomalies, and relatively high Th/Nb (0.7-0.8) and low Nb/La (0.4-0.6) ratios. The gabbro specimen has negative εNd(t) (-6.3--3.0) and positive εHf(t) (8.0-12.1), indicating it is sourced from depleted mantle with the addition of enriched components. In combination with the regional geology, we infer the gabbro is derived from depleted mantle wedge metasomatized by sediment-derived fluids and formed in the active continental margin in a subduction setting.

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    Magmatic epidote in Quanganglintou gneissic dacodiorite from the Changle-Nan’ao structural zone: Discovery and geological significance
    CUI Xianyue, CHEN Bolin, SI Xiaobo, DENG Jinfu, FENG Yanfang, XIAO Qinghui
    2022, 29(2): 234-240. 
    DOI: 10.13745/j.esf.sf.2021.10.40

    Abstract ( 227 )   HTML ( 12 )   PDF (7644KB) ( 106 )  

    Magmatic epidote can be used as a pressure gauge to reflect the emplacement depth of the rock mass, from which the rate of crustal uplift and denudation and the history of crustal evolution can be assessed. Magmatic epidote in Quangangintou gneissic tonalite from the Changle-Nan’ao structural belt is the fifth epidote occurrence reported in China and the first discovered in the southeast coastal area. The gneissic tonalite, formed in the Early Cretaceous (K1), is dominated by calcic, medium-potassium, calc-alkaline series and metaluminous, weak peraluminous, calc-alkaline series, possessing the properties of magnesium andesite and showing the trondhjemite evolutionary trend. Light rare earth elements are relatively enriched in the gnessic tonalite, with no obvious negative Eu anomaly. Large Ta, P and Ti negative anomalies show the characteristics of volcanic arc granites in orogenic belts. As revealed by petrographic analysis, the biotite and automorphic epidote are distributed in the gaps in plagioclase forming a typical filling structure. The two minerals, wrap around each other, appear as primary minerals co-crystallized from the late water-rich magma, not secondary ones formed after the magmatic period of metasomatic plagioclase. By EPMA analysis, the power factor Ps for the epidote is between 24-29, and TiO2 content is less than 0.1%. Petrographic and chemical analyses further reveal the epidote in gneissic tonalite is magmatic epidote, formed underground at a pressure of ~8.7 kbar and a depth of 25-32 km. Combining the above results with the crustal thickness of ~30 km for the present southeast coast continent, the corresponding Early Cretaceous (K1) crustal thickness is estimated at about 55-62 km. After the Early Cretaceous (K1), the crust might have experienced multiple uplifts.

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    Granitic magmatism and tectonic evolution in the Qilian Mountain Range in NW China: A review
    ZHU Xiaohui, CHEN Danling, FENG Yimin, REN Yunfei, ZHANG Xin
    2022, 29(2): 241-260. 
    DOI: 10.13745/j.esf.sf.2021.10.39

    Abstract ( 324 )   HTML ( 27 )   PDF (8590KB) ( 427 )  

    The Qilian Mountain is a composite orogenic belt that has experienced multicyclic tectonic movements, and granitic magmatism plays an important role in the tectonic evolution of such an orogenic belt. According to zircon U-Pb geochronology results, granitic magmatism in the Qilian Mountain can be divided into seven major stages. The Early Paleoproterozoic (2470-2348 Ma) granitic magmatism is related to high-K calc-alkaline strongly peraluminous S-type granites and tholeiitic to high-K calc-alkaline metaluminous I-type granites, which recorded the crustal accretion and transformation events of this period. The Late Paleoproterozoic (1778-1763 Ma) granitic magmatism is predominantly associated with high-K calc-alkaline shoshonitic metaluminous to weakly peraluminous A-type granites formed as a result of the breakup of the Columbia supercontinent. The Late Mesoproterozoic to Early Neoproterozoic (1192-888 Ma) granitic magmatism is mainly related to calc-alkaline shoshonitic peraluminous to strongly peraluminous S-type granites, while the Middle Neoproterozoic (853-736 Ma) granitic magmatism is primarily associated with calc-alkaline to high-K calc-alkaline metaluminous to strongly peraluminous A-type granites, and, respectively, they correspond to the assembly and breakup of the Rodinia supercontinent. The Middle Cambrian to Silurian (516-419 Ma) granitoids are formed during ocean-continent transition, whilst the widely distributed low-Mg adakites (Ca. 440 Ma), derived from the partial melting of thickened crust, indicate the Qilian orogenic belt had fully entered the collisional orogenic period. The Devonian to Early Carboniferous (418-350 Ma) granitoids are formed in the post-collisional environment and consist a series of granites with rock types ranging from tholeiitic to shoshonitic, metaluminous to strongly peraluminous. The Middle Permian to Late Triassic (271-211 Ma) granitoids are dominated by calc-alkaline to high-K calc-alkaline metaluminous to weakly peraluminous I-type granites, with small amounts of high-K calc-alkaline weakly peraluminous A-type granites; respectively, these two types are associated with oceanic subduction and post-collisional extension.

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    Late Paleozoic crustal composition and growth in West Junggar: Evidence from Sr-Nd-Pb isotopic mapping
    XU Shenglin, DING Weicui, CHEN Xuanhua, LI Tingdong, HAN Lele, LIU Yong, MA Feizhou, WANG Ye
    2022, 29(2): 261-280. 
    DOI: 10.13745/j.esf.sf.2022.2.8

    Abstract ( 174 )   HTML ( 8 )   PDF (18808KB) ( 458 )  

    The West Junggar region has experienced intense Late Paleozoic magmatic activity, where vertical and lateral crustal accretion is significant and crustal growth and evolution is multi-stage. Focusing on Sr-Nd-Pb isotopic mapping, this study found that the West Junggar region has the isotopic characteristics of high positive εNd(t) value of 2.29-8.75, low ( 87Sr/86Sr)i ratio of 0.697397-0.708336, and (206Pb/204Pb)i ratio of 17.4975-19.0352; it has a young crustal model age by calculation. The source area is dominated by Paleozoic new crust, with mantle contribution greater than 50%, and there is almost no old crystalline basement in the deep crust, which is in agreement with regional tectonic geological and geophysical data. The West Junggar region mainly experienced three orogenic stages in the Late Paleozoic: arc-dominated lateral growth in the Middle-Late Carboniferous; post-collision vertical growth in the Late Carboniferous-Early Permian; and vertical growth in the Early Permian-Triassic with crust-mantle mixed source. Regional orogenesis ends in the Early Triassic.

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    Basic geological characteristics of the East China Sea region and geological-geophysical characterization of some important tectonic boundaries in the region
    HOU Fanghui, ZHU Xiaoqing, ZHANG Xunhua, WU Zhiqiang, GUO Xingwei, QI Jianghao, WEN Zhenhe, WANG Baojun, MENG Xiangjun
    2022, 29(2): 281-293. 
    DOI: 10.13745/j.esf.sf.2021.10.37

    Abstract ( 300 )   HTML ( 13 )   PDF (15425KB) ( 213 )  

    Based on a comprehensive analysis of the geological and geophysical data of the East China Sea region, especially the latest geophysical data from the past ten years, the basic geological characteristics of the research area were sorted out, and the extension of the continental tectonic units in the sea area was discussed. The results showed that the Bohai Sea and the northern Yellow Sea are typical North China style basement where North China style sedimentary caprock is developed. The South Yellow Sea is typical Yangtze style oceanic basement and developed Yangtze style sedimentary caprock. The East China Sea shelf is Cathaysia type basement, and the eastern part is likely to have Late-Paleozoic sedimentary caprock overlaid by that of the Late Triassic. The western side of the lower Yangtze Block is wedged into the North China Block through the sinistral strike-slip Tanlu Fault Zone, while the eastern side is wedged through the dextral strike-slip fault zone in the western margin of the Korean Peninsula. The fault zone of the western margin of the Korean Peninsula has the characteristics of both strike-slip and subduction zones. The whole Korean Peninsula is similar to the North China Block in terms of metamorphic basement and sedimentary cover. The lower crust beneath the Yangtze Block is subducted north-eastward under the North China Block, while the upper crust is thrust upward over the North China Block. The Jiangshan-Shaoxing Suture Zone is a 50-70 km wide high magnetic anomaly belt in the NE direction. After entering the Hangzhou Bay, it turns to the EW direction, passing through the Daqushan Island of Zhoushan Islands then over the Hupi Reef Uplift of the East China Sea shelf to enter the Kyushu Island of Japan. The Hupi Reef Uplift is a set of subduction accretion complex, similar to the Daqushan Island.

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    Mesozoic basin evolution and hydrocarbon potential in the northern South China Sea and southern East China Sea
    WANG Mingjian, PAN Jun, GAO Hongfang, HUANG Long, LI Xia
    2022, 29(2): 294-302. 
    DOI: 10.13745/j.esf.sf.2021.7.8

    Abstract ( 255 )   HTML ( 6 )   PDF (8452KB) ( 158 )  

    The current exploration results show that the Mesozoic strata are widely developed in the vase sea area from the northern South China Sea to southern East China Sea. However, no major exploration breakthroughs in the Mesozoic strata has been made except for the discovery of industrial oil and gas reservoirs in the southwestern Taiwan basin. In this study, the Mesozoic strata across this entire sea area were studied as a whole, where an unified tectonic background analysis was conducted to uncover the nature of this large basin as well as its formation and evolution mechanism in each tectonic period; the hydrocarbon resource potential in the Mesozoic strata was also explored. The results show that this large basin spans from the Late Triassic to Cretaceous, and the evolution of the basin is controlled by the mutual movements of the surrounding plates. The basin is mainly controlled by the Tethys structural domain in the Late Triassic (T3), and its nature is passive continental margin marine sedimentary basin. From the Early Jurassic (J1) to Early Cretaceous the basin is controlled by the subduction between the Paleo-Pacific plate (izonesaki plate) and Eurasian plate, where fore-arc depression basin from the Early-Middle Jurassic (J1-2) and back-arc fault basin from the Late Jurassic to Early Cretaceous (J3-K1) are developed. Presently, it is still a back-arc fault basin in the Late Cretaceous (K2) under the joint control of the Pacific, Eurasian and Indian plates, with increased intensity of rifting compared with the previous period. The sea water intrudes from the southeast direction, and the stratum transits from the sea to the land vertically. From south to the northwest and northeast, with the water depth gradually becoming shallow, the stratum also transits from the sea to the land. The Mesozoic developed deep-sea facies and bay facies mudstones in the Chaoshan depression of the northern South China Sea, and bay facies mudstones in the Jilong depression of the southern East China Sea, with great hydrocarbon generation potential. Overall, the Mesozoic strata have the material basis and geological conditions for forming large oil and gas reservoirs with great exploration potential. The results of this study can provide a basis for the exploration of Mesozoic oil and gas resources in this vast sea area.

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    Palynological study of the Late Oligocene-Early Pleistocene in Leizhou Peninsula, Guangdong
    ZHANG Zongyan, LIU Xiang, LI Xiang, KE Xue, ZHANG Jianyu, XU Yadong
    2022, 29(2): 303-316. 
    DOI: 10.13745/j.esf.sf.2022.2.9

    Abstract ( 238 )   HTML ( 7 )   PDF (10567KB) ( 119 )  

    The drill core ZKA01 from Leizhou Peninsula, Guangdong Province, revealed a Cenozoic stratigraphic sequence consisting of, upward from the bottom, the Oligocene Weizhou Formation, the Miocene Xiayang, Jiaowei, and Dengloujiao Formations, the Pliocene Wanglougang Formation, the Lower-Pleistocene Zhanjiang Formation, and the Middle Pleistocene Beihai Formation, where the Weizhou-Wanglougang Formations consist of littoral-neritic deposits, and the Zhanjiang-Beihai Formations consist of continental fluvial and lacustrine deposits. In this paper, 42 common seed plants, from 81 species identified from 29311 pollen fossil grains obtained from 88 layers in core ZKA01, were selected to reconstruct the paleoclimate parameters by the coexistence approach. It was found the Late Oligocene-Early Pleistocene paleoclimate sequence can be divided into four stages: the Late Oligocene-Early Miocene (25-17 Ma), Middle Miocene (17-13.5 Ma), Late Miocene-Pliocene (13.5-4 Ma), and Pliocene-Early Pleistocene (4-1.5 Ma) stages. The study area’s paleoclimate change pattern through the four stages can match the trend of global climate change rather well. The period of decreasing temperature in the Late Oligocene-Early Miocene roughly coincides with the Mi1a climate cooling event, whilst the climate change in the Middle Miocene corresponds to the Middle Miocene Climatic Optimum (MMCO), which is characterized by a hot, humid climate; in the late Middle Miocene temperature drops in response to the Mi3 cooling event to certain extent.

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    Surface sediments of an alkaline lake in the Otindag sandy land: Grain size and sedimentary organic matter variations and their environmental significance
    TIAN Fei, WANG Yong, YUAN Lupeng, TANG Wenkun
    2022, 29(2): 317-326. 
    DOI: 10.13745/j.esf.sf.2021.10.38

    Abstract ( 164 )   HTML ( 9 )   PDF (9804KB) ( 97 )  

    The spatial characteristics of grain size distribution, total organic matter (TOC) and stable carbon isotopic composition (δ13CTOC) in surface sediments of a desiccating alkaline lake in the southern Otindag sandy land were studied to explore their environmental implications. We found that clay and silt fractions were dominated in water surface and desiccated lakebed while TOC concentrations were generally less than 1% in most surficial samples. In the halophytic meadow to the east, the sand fraction moderately increased while TOC increased up 10.75% on average. From west to east, δ13CTOC became more negative from the lake (-24.88‰) to desicacated lakebed (-25.17‰) and halophytic meadow (-27.93‰) areas. End-member mixing analysis (EMMA) showed that the increases in the saltation and creeping end members were correlated to lake regression and vegetation degradation in the catchment. For Qrdin Nuur, the relatively low TOC and depleted δ13CTOC might indicate the absence of hydrophytes and major contributions of terrestrial C3 plants to sedimentary organic matter. Furthermore, when the seasonal lake dries up, the bared lakebed, composed mainly of clay and silt fractions, would experience strong wind erosion, leading to increased sand fraction and reduced salinity therefore the invasion of halophytes. Then TOC increased significantly following the appearance of halophytes, and the subsequent succession of vegetation and the increasing C3 biomass would likely lead to a decline in δ13CTOC. Thus, by studying the modern sedimentary processes and mechanism of Qrdin Nuur, we have deepened our understanding of the sedimentation and ecological evolution in desiccating alkaline lakes in the Otindag sandy land, thereby providing an important basis for paleoenvironmental reconstruction.

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    Application of biomarkers in reconstructing marine and lacustrine paleoecosystems and paleoproductivity: A review
    LING Yuan, WANG Yong, WANG Shuxian, SUN Qing, LI Haibing
    2022, 29(2): 327-342. 
    DOI: 10.13745/j.esf.sf.2021.10.35

    Abstract ( 520 )   HTML ( 28 )   PDF (1702KB) ( 250 )  

    Oceans and lakes have profound regulatory effects on climate, environment and ecosystems. Understanding the composition, structure and evolution of marine and lake biomes of ecosystems in different geological periods can provide a scientific basis for solving the current environmental problems and assessing sustainable development. Biomarkers enable us to study the evolution of various organisms at the molecular level due to their biological specificity. This paper summarizes the characteristics and sources of biomarkers (alkanes, acids, alcohols, ketones, esters, steroids, hopanoids, terpenes and glycerol tetraethers, etc.) in marine and lacustrine ecosystems. Biomarkers derived from terrestrial higher plants include long-chain alkanes, fatty acids, fatty alcohols, lignin, terpenes, etc., while derived from aquatic microalgae they include long-chain alkenones, alkyl diols, highly-branched isoprenoids (HBIs), etc. Biomarkers of microbial origin include bacteriohopanepolyols (BHPs), heterocyst glycolipids, branched alkanes, etc. In the future, biomarker analysis using compound-specific isotopes, combined with modern molecular biology studies, such as genomics and proteomics, ecological research on biological species corresponding to different biomarkers, and studying ancient and modern ecology jointly can provide a new feasible way for researching the molecular sources for certain biomarkers. This paper also rivews the application of biomarker indices in reconstructing the composition, structure, productivity and nutritional status of marine and lake ecosystems. Future research tends to shift from qualitative to quantitative reconstruction. More and more mature indices applied in oceans will be used in lacustrine environment. In addition, the combination of multiple indices will improve the reliability of reconstructing paleoecosystem.

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    Design of spatial database for the geological map of the Moon
    JIN Ming, DING Xiaozhong, HAN Kunying, LIU Jianzhong, LING Zongcheng, XU Kejuan, PANG Jianfeng, SHAO Tianrui
    2022, 29(2): 343-353. 
    DOI: 10.13745/j.esf.sf.2021.7.12

    Abstract ( 253 )   HTML ( 11 )   PDF (7303KB) ( 118 )  

    China is about to complete the compilation of its 1: 2.5 million digital geological map of the entire lunar surface. In order to facilitate the storage, management, integration and sharing of the geological map data, it is necessary to build a comprehensive and practicable spatial database. In this paper, the geological spatial database feature classes were catalogued and classified comprehensively through mapping exercise. The feature class contains four main categories-material class, structural class, other special symbols class and annotation class, which are subdivided into 13 subcategories and 40 further subcategories. Extensible classification codes were designed based on this classification scheme. Spatial feature classes are organized and managed using layers. The layer name is formed as follows: the first four bits are the map number, the fifth bit is the scale code, and the following is the abbreviation of the English name of the layer. Each layer is associated with an attribute table. The field name, alias, type, empty or not, length, decimal places and units of all fields in the attribute table were defined and standardized. As an example the structure of the attribute table for crater materials, mare basalts, impact fractures and elevation points are described in detail. The primary key of the attribute table is “Feature_ID”, which is used to uniquely identify an element. The “Feature_ID” is composed of four 14-bit codes: map number, scale bar code, classification code and element sequence code. The database is designed following the principle of scalability so it can be referenced by spatial databases for other map areas or scales. Here, the design of a spatial database for the geological map of von Carmen impact crater is presented. Scientific and practicable database design is the premise of database construction, and it will play an important part in storage management and international sharing of the lunar mapping results.

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    Compilation of the geological map of the Petavius quadrangle of the Moon (LQ-21) and study on the regional geological evolution
    XU Kejuan, DING Xiaozhong, HAN Kunying, LIU Jingwen, LING Zongcheng, PANG Jianfeng, WANG Ying
    2022, 29(2): 354-369. 
    DOI: 10.13745/j.esf.sf.2021.3.11

    Abstract ( 175 )   HTML ( 5 )   PDF (20303KB) ( 248 )  

    The Petavius quadrangle (LQ-21) is located at the junction of the near and far sides of the Moon in the transition zone between the mare and highland terrain. Large impact basins such as Nectaris, Foecunditatis, and Smythii basins are developed around this region. Understanding the geological development of this area is helpful for understanding the development and evolutionary history of the Moon. Accordingly, this area is a key area in the digital geological mapping of the Moon. This work combines the Chang’E-1(CE-1) CCD image data, interference imaging spectrometer(IIM) data, laser altimeter (LAM) data, Chang’E-2(CE-2) CCD image data, as well as other lunar geological data, to study the material composition, structural elements, and geochronology of the lunar surface, and to compile the lunar geological map using the ArcGIS platform. So far, we have completed the geological map of the Petavius quadrangle at 1: 2.5 million scale, summarized the regional geological evolutionary history, and established a spatial database for the geological map of this region.

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    Updating basic geological data: Current status at home and abroad and suggestions for future improvements
    FENG Yanfang, LIU Jiangtao, LIU Yong, CUI Xianyue, SI Xiaobo
    2022, 29(2): 370-377. 
    DOI: 10.13745/j.esf.sf.2021.10.41

    Abstract ( 412 )   HTML ( 18 )   PDF (5306KB) ( 257 )  

    Geological research, driven by Big Data, cloud computing, mobile internet and other information technologies, has seen a paradigm shift from empirically and theoretically oriented to data intensive research. Basic geological data acquired through basic, strategic and public national geological survey reflect the accuracy and quality of the survey. They are the basis and source of innovation, service and sustainable development of geological survey and determine the strategic planning and competitiveness of future geological survey. With the coming of the fourth paradigm in scientific research, the quantity, quality and renewal time of basic geological data have become one of the basic standards to measure the overall quality of national geological survey. Most countries, according to strict technical standards, have achieved real-time updating of basic geological database and integration of basic geological data and maps, and have developed a variety of geological data-based products to meet societal needs. In China, although the Geological Cloud 3.0 platform has been built to achieve the integration and sharing of a number of databases, factors such as imperfect data updating mechanism, lack of data updating standards/technology and insufficient research and service development for basic geological data have, respectively, affected the macro-scale geological cognition capability, restricted the support and service role of geological survey and limited the external demand for data renewal. Thus, we put forth in this paper some suggestions on building a basic geological data updating system based on the Geological Cloud 3.0 platform: 1. Establish an integrated “cloud-nodes” data updating working mechanism. 2. Establish unified national data updating standards. 3. Build a “Big Data, AI and online-based” technological system. 4. Build a stable and collaborative multi-party working team. This paper is dedicated to Academician Li Tingdong, the Chief Scientist in the “National Basic Geological Data Update and Integration Project”, in celebrating his 90th Birthday and thanking him for his guidance, advice and kindness for the past 10+ years.

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    Detailed structure of the Earth’s crust and upper mantle of the Severomuysk segment of the Baikal rift zone according to teleseismic data
    Valentina V. MORDVINOVA, Maria A. KHRITOVA, Elena A. KOBELEVA, Mikhail M. KOBELEV, Evgeniy Kh. TURUTANOV, Victor S. KANAYKIN
    2022, 29(2): 378-392. 
    DOI: 10.13745/j.esf.sf.2022.2.1

    Abstract ( 290 )   HTML ( 9 )   PDF (8420KB) ( 99 )  

    The records of distant strong earthquakes, obtained by way of a dense linear network of seismic stations in the Severomuysk segment of the Baikal rift system, revealed a complex layered-block structure of the Earth’s crust and subcrustal mantle using the longitudinal receiving function. The distribution of cross-wave velocities indicates that the properties of the blocks that make up the Severomuysk Earth’s crust differ. The western vergence of these blocks and the stratification of the lower part of the Earth’s crust confirm the accretion-collision origin of the uplift. The intensity of the collision effect on the Earth’s crust of the region is explained by the location of the Severomuysk segment on the thinned inclined edge of the Siberian Craton. A convincing correlation was found between the focal depths of earthquakes in 2015 and contrasting velocity heterogeneities in the upper part of the Earth’s crust of the Muyakan depression.

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    Electrical resistivity structure beneath the central Cona-Oiga rift, southern Tibet, and its implications for regional dynamics
    XUE Shuai, LU Zhanwu, LI Wenhui, WANG Guangwen, WANG Haiyan, LIANG Hongda
    2022, 29(2): 393-401. 
    DOI: 10.13745/j.esf.sf.2022.2.3

    Abstract ( 252 )   HTML ( 13 )   PDF (4628KB) ( 160 )  

    As one of the most significant extensional structural styles of the Tibetan Plateau, the rifts in southern Tibet are an important window for studying the growth of the plateau. However, the formation mechanism of these deep rifts remains controversial. In this paper, magnetotelluric data from the central part of the Cona-Oiga rift were used to study the rifts in southern Tibet. The Magnetotelluric sounding curves and phase tensors were calculated and analyzed, and the electrical resistivity structure beneath the Qiongduojiang and Oiga grabens was obtained through 3D MT inversion. The 3D inversion result showed that an obvious continuous high-conductivity anomaly develops beneath the Cona-Oiga rift in a “subduction” pattern overlaying with high-resistivity structures, while low-resistivity anomalies distribute in the relatively shallow parts beneath either side of the Qiongduojiang graben. Combined with the previous studies, the continuous high-conductivity anomaly beneath the Cona-Oiga rift is believed to be originated from crustal partial melting, probably related to the southward crustal flow. We suggest that, under the N-S compression driven by the India-Eurasia collision, the weakened crust promotes the development of the rifts in southern Tibet by decoupling the upper crust and the lower lithosphere.

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    2D Tomographic imaging of the P-wave velocity structure in the upper crust beneath the southern Beishan tectonic belt
    WU Guowei, XIONG Xiaosong, GAO Rui, CHEN Xuanhua, LI Yingkang, WANG Guan, WANG Xiaocheng, REN Haidong
    2022, 29(2): 402-415. 
    DOI: 10.13745/j.esf.sf.2022.2.2

    Abstract ( 212 )   HTML ( 19 )   PDF (16930KB) ( 272 )  

    The Huahai Basin-Beishan tectonic belt is located north of the northeastern margin of the Qinghai-Tibetan Plateau and is the junction zone connecting the Tethys and Paleo-Asian Ocean domains. Since the Late-Neoproterozoic it has undergone multi-era, multi-stage evolution involving multiple plate splitting, subduction, collision and merging events. The subsequent overthrusting and strike-slip faulting since the Mesozoic, in particular the northward expansion of the northeastern margin of the Tibetan Plateau caused by the far-field effect of the collision between the Indian and Eurasian plates in the Cenozoic, formed the present complex geological/geomorphological structure. The crustal structure records the overprinting of the tectonics, whereas the upper crust is a natural notebook valuable for understanding the outward growth of the NE Tibet and its role in the transformation of the adjacent tectonic units. In this paper, based on the first arrive seismic wave (Pg phase) data from the 180 km-long deep seismic reflection profile completed by the Chinese Academy of Geological Sciences in 2018, we applied the tomographic inversion method to determine the P-wave velocity structure in the upper crust beneath the Huahai Basin-southern Beishan tectonic belt, 0-4 km deep underground. It was found that the three basins, Huahai, Zongkouzi and Zhagehao Basins, have a relatively low P-wave velocity and small vertical velocity gradient; the Late-Paleozoic granite outcrop shows obvious high-velocity anomalies and large vertical velocity gradient; and the left strike-slip Altyn fault zone across the southern margin of the Huahai Basin is a north-dipping high-angle strike-slip fault as deep as cutting through the basin basement at the least. In addition, many low-velocity anomalies revealed the extend of fault development in the southern Beishan.

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    Continent-continent collision at the southwestern margin of the Cretaceous Qiangtang terrane: Constraints from granite in the western Bangong-Nujiang Suture Zone
    FU Shun, ZHAO Yingquan, WANG Jinjun, YU Yu, ZHU Yingtang, FU Xingzhe
    2022, 29(2): 416-430. 
    DOI: 10.13745/j.esf.sf.2021.10.50

    Abstract ( 225 )   HTML ( 7 )   PDF (6973KB) ( 143 )  

    A large number of moderately felsic to basic intrusive rocks in the forms of rock strains or rock branches are distributed in the southwestern margin of the Qiangtang terrane. These intrusive rocks are characterized by petrographic analysis as peraluminous granite with low SiO2 (67.99%-73.32%) and high Al2O3 (12.82%-15.02%) contents, and defined as calc alkaline based on the Ritmann serial indices of 2.09-2.63 (σ<3.3). They show strong enrichment of light rare earth elements (REE) and strong depletion of heavy REE, with a high degree of magma crystallographic differentiation. The geochemical characteristics of the rocks and REE in granite indicate its tectonic environment is mainly type I, with some variability, and its formation and intrusion should be related to the closure of the ancient Tethys Ocean and the expansion of the new Tethys Ocean, which suggests an intracontinental collisional orogenic granite origin. The zircon laser ablation inductively coupled plasma-mass spectrometry (LA-ICPMS) dating of several granite masses in this area yielded a formation age of 107-116 Ma, which is consistent with the time of continent-continent collision at the southern margin of the Qiangtang terrane in the late Early Cretaceous.

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