The Triassic was a crucial period in the tectonic evolution of the South China Block.Research on tectonic deformation during this period provides information on intracontinental orogenic mechanisms in South China.In t...The Triassic was a crucial period in the tectonic evolution of the South China Block.Research on tectonic deformation during this period provides information on intracontinental orogenic mechanisms in South China.In this study,alongside thermochronological analyses,we examine the macroscopic and microscopic structural features of the Rongxian ductile shear zone,located south of the Darongshan granite in the southeastern part of Guangxi Province,on the southern margin of South China.Sinistral shear is indicated by the characteristics of rotatedσ-type feldspar porphyroclasts,stretching lineations defined by elongated quartz grains and the orientations of quartz c-axes.LA-ICP-MS U-Pb dating of zircons from two samples of granitic mylonite and one of granite yielded ages of ca.256 Ma.Furthermore,two samples of granitic mylonite yield muscovite^(40)Ar/^(39)Ar plateau ages of 249-246 Ma.These results indicate that the Rongxian ductile shear zone resulted from Early Triassic deformation of the late Permian Darongshan granite.This deformation was likely related to the closure of the eastern Paleo-Tethys Ocean and the subsequent collision of the South China and Indochina blocks,during the early stage of the Indosinian orogeny.展开更多
The exploration of unconventional and/or new energy resources has become the focus of energy research worldwide,given the shortage of fossil fuels.As a potential energy resource,gas hydrate exists only in the environm...The exploration of unconventional and/or new energy resources has become the focus of energy research worldwide,given the shortage of fossil fuels.As a potential energy resource,gas hydrate exists only in the environment of high pressure and low temperature,mainly distributing in the sediments of the seafloor in the continental margins and the permafrost zones in land.The accurate determination of the thickness of gas hydrate stability zone is essential yet challenging in the assessment of the exploitation potential.The majority of previous studies obtain this thickness by detecting the bottom simulating reflectors(BSRs) layer on the seismic profiles.The phase equilibrium between gas hydrate stable state with its temperature and pressure provides an opportunity to derive the thickness with the geothermal method.Based on the latest geothermal dataset,we calculated the thickness of the gas hydrate stability zone(GHSZ) in the north continental margin of the South China Sea.Our results indicate that the thicknesses of gas hydrate stability zone vary greatly in different areas of the northern margin of the South China Sea.The thickness mainly concentrates on 200–300 m and distributes in the southwestern and eastern areas with belt-like shape.We further confirmed a certain relationship between the GHSZ thickness and factors such as heat flow and water depth.The thickness of gas hydrate stability zone is found to be large where the heat flow is relatively low.The GHSZ thickness increases with the increase of the water depth,but it tends to stay steady when the water depth deeper than 3 000 m.The findings would improve the assessment of gas hydrate resource potential in the South China Sea.展开更多
The paleocontinental margins have frequent and intensive tectonic movement and various ore forming processes. According to their tectono dynamic characteristics, the paleocontinental margins can be classified into t...The paleocontinental margins have frequent and intensive tectonic movement and various ore forming processes. According to their tectono dynamic characteristics, the paleocontinental margins can be classified into three types: the divergent, the convergent and the transformational. Each type has its specific geological geochemical processes and metallogenic system. The paper discusses the tectonic evolution and ore forming features of the North China block margins, puts forward conceptions such as complexity, variety and multi stage development of metallogenic evolution in the paleocontinental margins, and expounds five factors controlling the formation of large superlarge ore deposits in the paleocontinental margins: (1) channelway, (2) rendezvous of fluids, (3) abundance of ore source, (4) thermo dynamic anomaly, (5) long duration of structural activities.展开更多
Several stratigraphic breaks and unconformities exist in the Mesoproterozoic successions in the northern margin of the North China Block. Geologic characters and spatial distributions of five of these un- conformities...Several stratigraphic breaks and unconformities exist in the Mesoproterozoic successions in the northern margin of the North China Block. Geologic characters and spatial distributions of five of these un- conformities, which have resulted from different geological processes, have been studied. The uncon- formity beneath the Dahongyu Formation is interpreted as a breakup unconformity, representing the time of transition from continental rift to passive continental margin. The unconformities beneath the Gaoyuzhuang and the Yangzhuang formations are considered to be the consequence of regional eustatic fluctuations, leading to the exposure of highlands in passive margins during low sea-level stands and transgressive deposition on coastal regions during high sea-level stands. The unconformity atop the Tieling Formation might be caused by uplift due to contractional deformation in a back-arc setting, whereas the uplift after the deposition of the Xiamaling Formation might be attributed to a continental collision event. It is assumed that the occurrences of these unconformities in the Mesoproterozoic successions in the northern margin of the North China Block had a close bearing on the assemblage and breakup of the Columbia and Rodinia supercontinents.展开更多
The western fault zone of the South China Sea is a strike-slip fault system and consists of four typical strike-slip faults. It is the western border of the South China Sea. The formation of the system is due to the e...The western fault zone of the South China Sea is a strike-slip fault system and consists of four typical strike-slip faults. It is the western border of the South China Sea. The formation of the system is due to the extrusion of Indo - China Peninsula caused by the collision of India with Tibet and the spreading of the South China Sea in Cenozoic. There are five episodes of tectonic movement along this fault zone, which plays an important role in the Cenozoic evolution of the South China Sea. By the physical modeling experiments, it can be seen the strike-slip fault undergoes the sinistral and dextral movement due to the relative movement velocity change between the South China Sea block and the Indo - China block. The fault zone controls the evolution of the pull basins locating in the west of the South China Sea.展开更多
Objective Indosinian magmatic rocks mainly locate in west Qinling Orogen, which are, however, extremely rare in east Qingling Orogen (Lu Xinxiang, 2000; Zhang Guowei et al., 2001; Guo Xianqing et al., 2017). The Zh...Objective Indosinian magmatic rocks mainly locate in west Qinling Orogen, which are, however, extremely rare in east Qingling Orogen (Lu Xinxiang, 2000; Zhang Guowei et al., 2001; Guo Xianqing et al., 2017). The Zhifang Huangzhuang (ZH) area in south Songxian County is located in the southern margin of the North China Craton (Fig. l a), which is an important lndosinian alkaline magmatic occurrence including 32 syenite bodies and syenitic dykes in east Qinling Orogen. There are five syenite bodes in the ZH area, i.e., the Lang'aogou, Mogou, Longtou, Jiaogou and Wusanggou from west to east (Fig. l b).展开更多
Global Positioning System (GPS) observations during four measurement campaigns from 1992 to 1999 are used in a study of the temporal and spatial variation characteristics of crustal deformation of active tectonic bloc...Global Positioning System (GPS) observations during four measurement campaigns from 1992 to 1999 are used in a study of the temporal and spatial variation characteristics of crustal deformation of active tectonic blocks in North China. The Euler vectors for these active blocks are determined on the basis of GPS velocities of a group relative stable points in 1992,1995,1996 and in 1996,1999 respectively. We have studied the relative motion between blocks at the boundaries and the intra block deformation field. We have also inverted the strain rate fields for these active blocks by bi cubic spline model based on the GPS velocity field. The results show that the intra block deformation rates are different from those in block boundary zones, and are also different in different periods; the deformational field is generally characterized by intra-block extension in North China.展开更多
Identifying distinct tectonic units is key to understanding the geotectonic framework and distribution law of oil and gas resources.The South China Sea and its adjacent areas have undergone complex tectonic evolution ...Identifying distinct tectonic units is key to understanding the geotectonic framework and distribution law of oil and gas resources.The South China Sea and its adjacent areas have undergone complex tectonic evolution processes,and the division of tectonic units is controversial.Guided by block tectonics theory,this study divide the South China Sea and its adjacent areas into several distinguished tectonic units relying on known boundary markers such as sutures(ophiolite belts),subduction-collision zones,orogenic belts,and deep faults.This work suggests that the study area is occupied by nine stable blocks(West Burma Block,Sibumasu Block,LanpingSimao Block,Indochina Block,Yangtze Block,Cathaysian Block,Qiongnan Block,Nansha Block,and Northwest Sulu Block),two suture zones(Majiang suture zone and Southeast Yangtze suture zone),two accretionary zones(Sarawak-Sulu accretionary zone and East Sulawesi accretionary zone),one subduction-collision zone(RakhineJava-Timor subduction-collision zone),one ramp zone(Philippine islands ramp zone),and six small oceanic marginal sea basins(South China Sea Basin,Sulu Sea Basin,Sulawesi Sea Basin,Banda Sea Basin,Makassar Basin,and Andaman Sea Basin).This division reflects the tectonic activities,crustal structural properties,and evolutionary records of each evaluated tectonic unit.It is of great theoretical and practical importance to understand the tectonic framework to support the exploration of oil and gas resources in the South China Sea and its adjacent areas.展开更多
: In this paper, 3-D velocity images of the crust and upper mantle beneath the Nanbei tectonic zone of China are constructed using P-wave travel time residuals of earthquakes, with the data supplied by China's sei...: In this paper, 3-D velocity images of the crust and upper mantle beneath the Nanbei tectonic zone of China are constructed using P-wave travel time residuals of earthquakes, with the data supplied by China's seismic networks and the International Seismic Centre.展开更多
The helium and argon isotopic compositions of the ore-forming fluids from the molybdenum deposits such as Jinduicheng, Donggou, Shijiawan, and Sandaozhuang, which are located in the East Qinling molybdenum belt in sou...The helium and argon isotopic compositions of the ore-forming fluids from the molybdenum deposits such as Jinduicheng, Donggou, Shijiawan, and Sandaozhuang, which are located in the East Qinling molybdenum belt in south margin of North China Block (SMCNB), are reported in this paper. The origin and the evolution of the ore-forming fluids and their coupled-relationships with the intra-continental collision and orogenic process of Qinling Orogen in Mesozoic-Cenozoic have been discussed. The 3He/4He and 40Ar/36Ar values (3He/4He=1.38―3.64 Ra, and 40Ar/36Ar=295.68―346.39, respectively) of the fluid inclusions in pyrite from the molybdenum deposits in East Qinling suggest that, the ore-forming fluid system is mixed by two end members. One is the high temperature deep-derived fluid congenetic with the porphyries generated by crust-mantle mixing, and the other is the low-temperature meteoric water which is rich in crustal radiogenic He with the component of atmospheric Ar. From the Pb isotopic composition, and ore-bearing potential of the porphyry and the regional stratum, we can conclude that the ore-forming materials of the deposits in the East Qinling molybdenum belt are derived from the deep source by the mixing of lower crust and upper mantle. Therefore, the formation of the molybdenum deposits in SMNCB can be related to the crust-mantle interaction, which is accompanied by the intra-continental orogenic and extension process in the post-collision period of Qinling Orogen. The granitic porphyries which are related to Mo mineralization are not simple crust-remelting type granites or S type granites, but belong to syntexis-type or mantle-derived granites, hence their formation has a profound and regional geodynamic background.展开更多
This paper aims to explore whether paleo-suture zone exists in the pre-Cenozoic basement of South China Sea (SCS). By taking advantage of integrated geophysical surveying data, including multi-channel reflection seism...This paper aims to explore whether paleo-suture zone exists in the pre-Cenozoic basement of South China Sea (SCS). By taking advantage of integrated geophysical surveying data, including multi-channel reflection seismicity, oceanic bottom seismicity, gravity and magnetic data as well as paleomagnetism and drilling information, a comprehensive analysis on sedimentary stratigraphy, seismic stratigraphy, magmatic and metamorphic petrology, geochemistry, gravity study, magnetics, paleogeomagnetics as well as geotectonics was carried out, and the results clearly indicate that a pre-Cenozoic suture zone, i.e. “Qiongnan (south Hainan Island) suture zone”, does exist on the north margin of SCS. This suture zone starts in the west from the Jiusuo-Lingshui fault zone in the south of Hainan Island, extends eastward across the continental slope to the north of SCS, and links with Shoufeng fault in Taiwan. It is inferred that the Qiongnan suture zone was sutured approximately in Indosinian (Triassic) Epoch and is actually the vestige of “Qiongnan ocean basin”, the extension of the main paleo-Tethys ocean basin in SCS. The formation of Qiongnan suture zone marked the collision-accretion of the Qiongnan Block toward the Qiongzhong Block. The Qiongnan suture zone is linked to the west with the southward extension of the principal suture zone of the Paleo-Tethys at Bitu-Changning-Menglian-Bentong-Raub, across the southern segment of the Red River-East Vietnam-Wanna strike-slip fault zone, and connected to the east with the suture zone emplaced into the south margin of the Oki-Hida Pre-Jurassic terranes in southwest Japan, across the northerni2 e segment of the Manila trench fault zone in the northeast side of Taiwan Island. The discovery of this suture zone is believed to be potentially significant toward study of the pre-Cenozoic geotectonic pattern of SCS, the temporal and spatial distribution of the east paleo-Tethys structural domain in SCS and the relationship of recombination and superimposition between the east paleo-Tethys structural domain and the west Pacific structural domain, in addition to the oil/gas geological potentials in the pre-Cenozoic marine vestige-superimposed basin in the study area.展开更多
Late Carboniferous fossils(such as Boultonia? sp., Tabulata, and spiriferoid specimens with smooth shells), bioclastic material(such as crinoid stems and sponge fragments), and Late Ordovician microfossils of the cono...Late Carboniferous fossils(such as Boultonia? sp., Tabulata, and spiriferoid specimens with smooth shells), bioclastic material(such as crinoid stems and sponge fragments), and Late Ordovician microfossils of the conodont Belodina have been discovered in the lower part of the strata typically referred to as the Neoproterozoic on the boundary of the provinces of Anhui and Henan in the southern margin of the North China Block. These findings prove that the strata contain macrofossils belonging to the Late Carboniferous, which belonged to a carbonate debris flow deposit that was formed under a carbonate slope environment. The conodont fossils might belong to a detrital deposit. Thus, it is possible to reset the stratigraphic sequences and tectonic attributes belonging to the North Huaiyang tectonic belt and limit the Shouxian fault to the boundary between the Dabie Orogen and North China Block.展开更多
The tectonic position of the southwest section of the Qinzhou Bay-Hangzhou Bay Tectonic Junction Zone(QHTJZ)can be determined by examining the Qinzhou-Fangcheng Junction Zone(QFJZ)in Guangxi.This zone is significant b...The tectonic position of the southwest section of the Qinzhou Bay-Hangzhou Bay Tectonic Junction Zone(QHTJZ)can be determined by examining the Qinzhou-Fangcheng Junction Zone(QFJZ)in Guangxi.This zone is significant because it was the location of the largest earthquake ever recorded in the inland region of South China,specifically the 1936 Lingshan M6^(3/4)earthquake in Guangxi.Therefore,this region serves as an optimal location for researching the origins of intraplate earthquakes in South China.This study presents a display of a broadband magnetotelluric(MT)prospecting profile that traverses the Guangxi QFJZ and the Lingshan earthquake zone,extending from the northwest(NW)to the southeast(SE).A resistivity structure model was generated using three-dimensional(3D)inversion technology along the profile.The main faults in QFJZ were analyzed in terms of their deep extension forms and tectonic attributes.This analysis was performed by integrating the results obtained from geology,gravity,wave velocity ratio,Global Position System(GPS),and geothermal flow.The results showed that(1)the Dongzhong-Xiaodong fault(DXf),the eastern Fangcheng-Lingshan fault(FLf2),and the eastern Hepu-Beiliu fault(HBf2)were all trans-crustal deep faults,and crust-mantle ductile shear zones developed in the deep part.Two electrical boundary zones,DXf and HBf2,were identified.DXf inclined towards the northwest,while HBf2 inclined towards the southeast.The FangchengLingshan fault(FLf)exhibits a tectonic style resembling a“flower”shape in the upper crust.In the deeper section,it is characterized by an electrical boundary zone that gradually slopes towards the southeast direction.(2)The Hunan-Guangxi Passive Continental Margin(HGPCM)on the NW side of DXf had a stratified resistivity structure and relatively stable Bouguer gravity anomalies,which conformed to the quasi-craton tectonic attribute of the local failure at the southeastern margin of the Yangtze Block(YB).The southeastern side of this block is marked by the presence of the QFJZ and Yunkai Magmatic Arc(YKMA).These areas exhibit varying Bouguer gravity anomalies,indicating a combination of high and low resistivity in their electrical structures.This suggests that this zone has undergone multiple stages of structural evolution and transformation.The giant high-resistivity body under the Qinzhou-Fangcheng Remnant Ocean Basin(QFROB)might be the trace left by the extinction of the South China Ocean and the collision orogeny between YB and the Cathaysian Block(CB).The presence of sublow-resistivity layers in the middle-lower crust between the Liuwandashan Magmatic Arc(LMA)and YKMA indicates that this particular zone is being influenced from a distance by magmatic activities originating from the Leiqiong mantle.(3)The focal area of the 1936 Lingshan earthquake was located in the brittle high-resistivity body with a low strain rate.Under the coupling action of NWW-SEE regional tectonic stress and deep thermodynamic force,the brittle high-resistivity body in the upper crust became the main body for accumulating the tectonic stress.The Lingshan earthquake occurred due to the dextral strike-slip fracture instability of FLf2,a rock layer with slightly lower strength in the sub-high-resistivity zone.This instability was triggered when the accumulated stress reached the ultimate rock strength.The unveiling of the seismogenic model of the Lingshan earthquake,as presented in this study,holds significant scientific importance in comprehending the factors contributing to intraplate earthquakes in the South China region.展开更多
With the summarization of the Early Paleozoic paleomagnetic data recently obtained from the three major blocks of China, the Early Paleozoic (i.e. Cambrian and Ordovician) paleogeographic positions of the North China,...With the summarization of the Early Paleozoic paleomagnetic data recently obtained from the three major blocks of China, the Early Paleozoic (i.e. Cambrian and Ordovician) paleogeographic positions of the North China, South China and Tarim blocks were discussed in detail. The North China, South China and Tarim blocks were inferred to be located adjacent to East Gondwana in low latitudes of the Southern Hemisphere during the Early Cambrian. During the Early-Middle Ordovician, the South China and Tarim blocks were also located in low latitudes of the Southern Hemisphere with some affinities of the Gondwanaland, whereas the North China block may have episodically separated from the Gondwanaland, and might be sited close to the North America and Siberia. The reestablished paleogeographic configurations are in agreement with the studies on the biogeography, paleoclimate and sedimental facies of the North China and South China blocks.展开更多
Based on the geothermal and gravitation methods, this paper investigated the rheological and thermal structure of the lithosphere under the northern margin of South China Sea. The result shows that the temperature of ...Based on the geothermal and gravitation methods, this paper investigated the rheological and thermal structure of the lithosphere under the northern margin of South China Sea. The result shows that the temperature of the upper crust is 150–300°C lower than that of the lower crust, and the viscous coefficient of the upper crust is 2–3 orders of magnitude larger than that of the lower crust. It reveals that the upper crust is characterized by brittle deformation while the lower crust by ductile deformation. A channel of lower-viscosity should be formed between the upper and lower crust when the lithosphere is scattered and spreads out toward ocean from northwest to southeast along the northern margin of South China Sea. And, a brittle deformation takes place in the upper part of the lithosphere while a ductile deformation takes place in the lower part of the lithosphere due to different viscous coefficients and temperature. The layered deformation leads the faulted blocks to rotate along the faulting and the marginal grabens to appear in the northern margin of South China Sea in Cenozoic tectonic expansion.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.42262026,42072259).
文摘The Triassic was a crucial period in the tectonic evolution of the South China Block.Research on tectonic deformation during this period provides information on intracontinental orogenic mechanisms in South China.In this study,alongside thermochronological analyses,we examine the macroscopic and microscopic structural features of the Rongxian ductile shear zone,located south of the Darongshan granite in the southeastern part of Guangxi Province,on the southern margin of South China.Sinistral shear is indicated by the characteristics of rotatedσ-type feldspar porphyroclasts,stretching lineations defined by elongated quartz grains and the orientations of quartz c-axes.LA-ICP-MS U-Pb dating of zircons from two samples of granitic mylonite and one of granite yielded ages of ca.256 Ma.Furthermore,two samples of granitic mylonite yield muscovite^(40)Ar/^(39)Ar plateau ages of 249-246 Ma.These results indicate that the Rongxian ductile shear zone resulted from Early Triassic deformation of the late Permian Darongshan granite.This deformation was likely related to the closure of the eastern Paleo-Tethys Ocean and the subsequent collision of the South China and Indochina blocks,during the early stage of the Indosinian orogeny.
基金The National Natural Science Foundation of China under contract No.41176037the Ministry of Science and Technology Project under contract No.2016ZX05026-002-007+1 种基金the New Century Excellent Talents Program of MOE under contract No.NCET-12-263Jiangsu Province College Student Scientific Training Program under contract No.XZ1210284007
文摘The exploration of unconventional and/or new energy resources has become the focus of energy research worldwide,given the shortage of fossil fuels.As a potential energy resource,gas hydrate exists only in the environment of high pressure and low temperature,mainly distributing in the sediments of the seafloor in the continental margins and the permafrost zones in land.The accurate determination of the thickness of gas hydrate stability zone is essential yet challenging in the assessment of the exploitation potential.The majority of previous studies obtain this thickness by detecting the bottom simulating reflectors(BSRs) layer on the seismic profiles.The phase equilibrium between gas hydrate stable state with its temperature and pressure provides an opportunity to derive the thickness with the geothermal method.Based on the latest geothermal dataset,we calculated the thickness of the gas hydrate stability zone(GHSZ) in the north continental margin of the South China Sea.Our results indicate that the thicknesses of gas hydrate stability zone vary greatly in different areas of the northern margin of the South China Sea.The thickness mainly concentrates on 200–300 m and distributes in the southwestern and eastern areas with belt-like shape.We further confirmed a certain relationship between the GHSZ thickness and factors such as heat flow and water depth.The thickness of gas hydrate stability zone is found to be large where the heat flow is relatively low.The GHSZ thickness increases with the increase of the water depth,but it tends to stay steady when the water depth deeper than 3 000 m.The findings would improve the assessment of gas hydrate resource potential in the South China Sea.
文摘The paleocontinental margins have frequent and intensive tectonic movement and various ore forming processes. According to their tectono dynamic characteristics, the paleocontinental margins can be classified into three types: the divergent, the convergent and the transformational. Each type has its specific geological geochemical processes and metallogenic system. The paper discusses the tectonic evolution and ore forming features of the North China block margins, puts forward conceptions such as complexity, variety and multi stage development of metallogenic evolution in the paleocontinental margins, and expounds five factors controlling the formation of large superlarge ore deposits in the paleocontinental margins: (1) channelway, (2) rendezvous of fluids, (3) abundance of ore source, (4) thermo dynamic anomaly, (5) long duration of structural activities.
文摘Several stratigraphic breaks and unconformities exist in the Mesoproterozoic successions in the northern margin of the North China Block. Geologic characters and spatial distributions of five of these un- conformities, which have resulted from different geological processes, have been studied. The uncon- formity beneath the Dahongyu Formation is interpreted as a breakup unconformity, representing the time of transition from continental rift to passive continental margin. The unconformities beneath the Gaoyuzhuang and the Yangzhuang formations are considered to be the consequence of regional eustatic fluctuations, leading to the exposure of highlands in passive margins during low sea-level stands and transgressive deposition on coastal regions during high sea-level stands. The unconformity atop the Tieling Formation might be caused by uplift due to contractional deformation in a back-arc setting, whereas the uplift after the deposition of the Xiamaling Formation might be attributed to a continental collision event. It is assumed that the occurrences of these unconformities in the Mesoproterozoic successions in the northern margin of the North China Block had a close bearing on the assemblage and breakup of the Columbia and Rodinia supercontinents.
基金Acknowledgements This research was supported by the National Natural Science Foundation of China under contract Nos 40476026 and 40406012, the National Natural Science Foundation of Guangdong Province under contract No. 04001309, and the Key Laboratory of Marginal Sea Geology Foundation of South China Sea Institute of 0ceanology, Chinese Academy of Sciences under contract No. MSGL0510. We are grateful to Yan Pin and Liu Hailing for their generous help in providing seismic profiles.
文摘The western fault zone of the South China Sea is a strike-slip fault system and consists of four typical strike-slip faults. It is the western border of the South China Sea. The formation of the system is due to the extrusion of Indo - China Peninsula caused by the collision of India with Tibet and the spreading of the South China Sea in Cenozoic. There are five episodes of tectonic movement along this fault zone, which plays an important role in the Cenozoic evolution of the South China Sea. By the physical modeling experiments, it can be seen the strike-slip fault undergoes the sinistral and dextral movement due to the relative movement velocity change between the South China Sea block and the Indo - China block. The fault zone controls the evolution of the pull basins locating in the west of the South China Sea.
基金supported by the National Nature Science Foundation of China(grant No.U1504405)
文摘Objective Indosinian magmatic rocks mainly locate in west Qinling Orogen, which are, however, extremely rare in east Qingling Orogen (Lu Xinxiang, 2000; Zhang Guowei et al., 2001; Guo Xianqing et al., 2017). The Zhifang Huangzhuang (ZH) area in south Songxian County is located in the southern margin of the North China Craton (Fig. l a), which is an important lndosinian alkaline magmatic occurrence including 32 syenite bodies and syenitic dykes in east Qinling Orogen. There are five syenite bodes in the ZH area, i.e., the Lang'aogou, Mogou, Longtou, Jiaogou and Wusanggou from west to east (Fig. l b).
文摘Global Positioning System (GPS) observations during four measurement campaigns from 1992 to 1999 are used in a study of the temporal and spatial variation characteristics of crustal deformation of active tectonic blocks in North China. The Euler vectors for these active blocks are determined on the basis of GPS velocities of a group relative stable points in 1992,1995,1996 and in 1996,1999 respectively. We have studied the relative motion between blocks at the boundaries and the intra block deformation field. We have also inverted the strain rate fields for these active blocks by bi cubic spline model based on the GPS velocity field. The results show that the intra block deformation rates are different from those in block boundary zones, and are also different in different periods; the deformational field is generally characterized by intra-block extension in North China.
基金The National Natural Science Foundation of China under contract Nos 41706055,41776072,41602092,4106035 and41776072the Natural Science Foundation of Guangdong Province under contract Nos 2018A030313168 and 2018B030311030the National Marine Geology Special Project under contract Nos DD20160147 and DD20189643。
文摘Identifying distinct tectonic units is key to understanding the geotectonic framework and distribution law of oil and gas resources.The South China Sea and its adjacent areas have undergone complex tectonic evolution processes,and the division of tectonic units is controversial.Guided by block tectonics theory,this study divide the South China Sea and its adjacent areas into several distinguished tectonic units relying on known boundary markers such as sutures(ophiolite belts),subduction-collision zones,orogenic belts,and deep faults.This work suggests that the study area is occupied by nine stable blocks(West Burma Block,Sibumasu Block,LanpingSimao Block,Indochina Block,Yangtze Block,Cathaysian Block,Qiongnan Block,Nansha Block,and Northwest Sulu Block),two suture zones(Majiang suture zone and Southeast Yangtze suture zone),two accretionary zones(Sarawak-Sulu accretionary zone and East Sulawesi accretionary zone),one subduction-collision zone(RakhineJava-Timor subduction-collision zone),one ramp zone(Philippine islands ramp zone),and six small oceanic marginal sea basins(South China Sea Basin,Sulu Sea Basin,Sulawesi Sea Basin,Banda Sea Basin,Makassar Basin,and Andaman Sea Basin).This division reflects the tectonic activities,crustal structural properties,and evolutionary records of each evaluated tectonic unit.It is of great theoretical and practical importance to understand the tectonic framework to support the exploration of oil and gas resources in the South China Sea and its adjacent areas.
文摘: In this paper, 3-D velocity images of the crust and upper mantle beneath the Nanbei tectonic zone of China are constructed using P-wave travel time residuals of earthquakes, with the data supplied by China's seismic networks and the International Seismic Centre.
基金Supported by the National Basic Research Program of China (Grant No. 2006CB403502)National Natural Science Foundation of China (Grant No.40872071)+1 种基金Program of State Key Laboratory of Ore Deposit Geochemistry, Chinese Academy of Sciences (Grant No. 20060)Fundation of Educational Bureau of Shaanxi Province (Grant No. 07JK414)
文摘The helium and argon isotopic compositions of the ore-forming fluids from the molybdenum deposits such as Jinduicheng, Donggou, Shijiawan, and Sandaozhuang, which are located in the East Qinling molybdenum belt in south margin of North China Block (SMCNB), are reported in this paper. The origin and the evolution of the ore-forming fluids and their coupled-relationships with the intra-continental collision and orogenic process of Qinling Orogen in Mesozoic-Cenozoic have been discussed. The 3He/4He and 40Ar/36Ar values (3He/4He=1.38―3.64 Ra, and 40Ar/36Ar=295.68―346.39, respectively) of the fluid inclusions in pyrite from the molybdenum deposits in East Qinling suggest that, the ore-forming fluid system is mixed by two end members. One is the high temperature deep-derived fluid congenetic with the porphyries generated by crust-mantle mixing, and the other is the low-temperature meteoric water which is rich in crustal radiogenic He with the component of atmospheric Ar. From the Pb isotopic composition, and ore-bearing potential of the porphyry and the regional stratum, we can conclude that the ore-forming materials of the deposits in the East Qinling molybdenum belt are derived from the deep source by the mixing of lower crust and upper mantle. Therefore, the formation of the molybdenum deposits in SMNCB can be related to the crust-mantle interaction, which is accompanied by the intra-continental orogenic and extension process in the post-collision period of Qinling Orogen. The granitic porphyries which are related to Mo mineralization are not simple crust-remelting type granites or S type granites, but belong to syntexis-type or mantle-derived granites, hence their formation has a profound and regional geodynamic background.
文摘This paper aims to explore whether paleo-suture zone exists in the pre-Cenozoic basement of South China Sea (SCS). By taking advantage of integrated geophysical surveying data, including multi-channel reflection seismicity, oceanic bottom seismicity, gravity and magnetic data as well as paleomagnetism and drilling information, a comprehensive analysis on sedimentary stratigraphy, seismic stratigraphy, magmatic and metamorphic petrology, geochemistry, gravity study, magnetics, paleogeomagnetics as well as geotectonics was carried out, and the results clearly indicate that a pre-Cenozoic suture zone, i.e. “Qiongnan (south Hainan Island) suture zone”, does exist on the north margin of SCS. This suture zone starts in the west from the Jiusuo-Lingshui fault zone in the south of Hainan Island, extends eastward across the continental slope to the north of SCS, and links with Shoufeng fault in Taiwan. It is inferred that the Qiongnan suture zone was sutured approximately in Indosinian (Triassic) Epoch and is actually the vestige of “Qiongnan ocean basin”, the extension of the main paleo-Tethys ocean basin in SCS. The formation of Qiongnan suture zone marked the collision-accretion of the Qiongnan Block toward the Qiongzhong Block. The Qiongnan suture zone is linked to the west with the southward extension of the principal suture zone of the Paleo-Tethys at Bitu-Changning-Menglian-Bentong-Raub, across the southern segment of the Red River-East Vietnam-Wanna strike-slip fault zone, and connected to the east with the suture zone emplaced into the south margin of the Oki-Hida Pre-Jurassic terranes in southwest Japan, across the northerni2 e segment of the Manila trench fault zone in the northeast side of Taiwan Island. The discovery of this suture zone is believed to be potentially significant toward study of the pre-Cenozoic geotectonic pattern of SCS, the temporal and spatial distribution of the east paleo-Tethys structural domain in SCS and the relationship of recombination and superimposition between the east paleo-Tethys structural domain and the west Pacific structural domain, in addition to the oil/gas geological potentials in the pre-Cenozoic marine vestige-superimposed basin in the study area.
基金supported by funds from the China Geological Survey(12120113094300)the National Natural Science Foundation of China(40972082 and 41172097)
文摘Late Carboniferous fossils(such as Boultonia? sp., Tabulata, and spiriferoid specimens with smooth shells), bioclastic material(such as crinoid stems and sponge fragments), and Late Ordovician microfossils of the conodont Belodina have been discovered in the lower part of the strata typically referred to as the Neoproterozoic on the boundary of the provinces of Anhui and Henan in the southern margin of the North China Block. These findings prove that the strata contain macrofossils belonging to the Late Carboniferous, which belonged to a carbonate debris flow deposit that was formed under a carbonate slope environment. The conodont fossils might belong to a detrital deposit. Thus, it is possible to reset the stratigraphic sequences and tectonic attributes belonging to the North Huaiyang tectonic belt and limit the Shouxian fault to the boundary between the Dabie Orogen and North China Block.
基金supported by the Science for Earthquake Resilience Program of the China Earthquake Administration(Grant Nos.XH24033B,XH22004YA)the Guangxi Scientific Research and Technology Development Plan Project(Grant Nos.1377002,14124004-4-8)the Earthquake Prediction Open Fund Project of China Earthquake Administration(Grant No.2021EF0F02)。
文摘The tectonic position of the southwest section of the Qinzhou Bay-Hangzhou Bay Tectonic Junction Zone(QHTJZ)can be determined by examining the Qinzhou-Fangcheng Junction Zone(QFJZ)in Guangxi.This zone is significant because it was the location of the largest earthquake ever recorded in the inland region of South China,specifically the 1936 Lingshan M6^(3/4)earthquake in Guangxi.Therefore,this region serves as an optimal location for researching the origins of intraplate earthquakes in South China.This study presents a display of a broadband magnetotelluric(MT)prospecting profile that traverses the Guangxi QFJZ and the Lingshan earthquake zone,extending from the northwest(NW)to the southeast(SE).A resistivity structure model was generated using three-dimensional(3D)inversion technology along the profile.The main faults in QFJZ were analyzed in terms of their deep extension forms and tectonic attributes.This analysis was performed by integrating the results obtained from geology,gravity,wave velocity ratio,Global Position System(GPS),and geothermal flow.The results showed that(1)the Dongzhong-Xiaodong fault(DXf),the eastern Fangcheng-Lingshan fault(FLf2),and the eastern Hepu-Beiliu fault(HBf2)were all trans-crustal deep faults,and crust-mantle ductile shear zones developed in the deep part.Two electrical boundary zones,DXf and HBf2,were identified.DXf inclined towards the northwest,while HBf2 inclined towards the southeast.The FangchengLingshan fault(FLf)exhibits a tectonic style resembling a“flower”shape in the upper crust.In the deeper section,it is characterized by an electrical boundary zone that gradually slopes towards the southeast direction.(2)The Hunan-Guangxi Passive Continental Margin(HGPCM)on the NW side of DXf had a stratified resistivity structure and relatively stable Bouguer gravity anomalies,which conformed to the quasi-craton tectonic attribute of the local failure at the southeastern margin of the Yangtze Block(YB).The southeastern side of this block is marked by the presence of the QFJZ and Yunkai Magmatic Arc(YKMA).These areas exhibit varying Bouguer gravity anomalies,indicating a combination of high and low resistivity in their electrical structures.This suggests that this zone has undergone multiple stages of structural evolution and transformation.The giant high-resistivity body under the Qinzhou-Fangcheng Remnant Ocean Basin(QFROB)might be the trace left by the extinction of the South China Ocean and the collision orogeny between YB and the Cathaysian Block(CB).The presence of sublow-resistivity layers in the middle-lower crust between the Liuwandashan Magmatic Arc(LMA)and YKMA indicates that this particular zone is being influenced from a distance by magmatic activities originating from the Leiqiong mantle.(3)The focal area of the 1936 Lingshan earthquake was located in the brittle high-resistivity body with a low strain rate.Under the coupling action of NWW-SEE regional tectonic stress and deep thermodynamic force,the brittle high-resistivity body in the upper crust became the main body for accumulating the tectonic stress.The Lingshan earthquake occurred due to the dextral strike-slip fracture instability of FLf2,a rock layer with slightly lower strength in the sub-high-resistivity zone.This instability was triggered when the accumulated stress reached the ultimate rock strength.The unveiling of the seismogenic model of the Lingshan earthquake,as presented in this study,holds significant scientific importance in comprehending the factors contributing to intraplate earthquakes in the South China region.
文摘With the summarization of the Early Paleozoic paleomagnetic data recently obtained from the three major blocks of China, the Early Paleozoic (i.e. Cambrian and Ordovician) paleogeographic positions of the North China, South China and Tarim blocks were discussed in detail. The North China, South China and Tarim blocks were inferred to be located adjacent to East Gondwana in low latitudes of the Southern Hemisphere during the Early Cambrian. During the Early-Middle Ordovician, the South China and Tarim blocks were also located in low latitudes of the Southern Hemisphere with some affinities of the Gondwanaland, whereas the North China block may have episodically separated from the Gondwanaland, and might be sited close to the North America and Siberia. The reestablished paleogeographic configurations are in agreement with the studies on the biogeography, paleoclimate and sedimental facies of the North China and South China blocks.
基金the National Natural Science Foundation of China (Grant Nos.49732005, 49733011) and the Chinese Academy of Sciences (Grant No. KZ951-A1-401). We wish to thank Prof. Xu Houze and Lu Yang for their contribution in gravitational model. The authors also than
文摘Based on the geothermal and gravitation methods, this paper investigated the rheological and thermal structure of the lithosphere under the northern margin of South China Sea. The result shows that the temperature of the upper crust is 150–300°C lower than that of the lower crust, and the viscous coefficient of the upper crust is 2–3 orders of magnitude larger than that of the lower crust. It reveals that the upper crust is characterized by brittle deformation while the lower crust by ductile deformation. A channel of lower-viscosity should be formed between the upper and lower crust when the lithosphere is scattered and spreads out toward ocean from northwest to southeast along the northern margin of South China Sea. And, a brittle deformation takes place in the upper part of the lithosphere while a ductile deformation takes place in the lower part of the lithosphere due to different viscous coefficients and temperature. The layered deformation leads the faulted blocks to rotate along the faulting and the marginal grabens to appear in the northern margin of South China Sea in Cenozoic tectonic expansion.