The pre-Cenozoic northern South China Sea(SCS)Basin basement was supposed to exist as a complex of heterogeneous segments,divided by dozens of N-S faulting.Unfortunately,only the Hainan Island and the northeastern SCS...The pre-Cenozoic northern South China Sea(SCS)Basin basement was supposed to exist as a complex of heterogeneous segments,divided by dozens of N-S faulting.Unfortunately,only the Hainan Island and the northeastern SCS region were modestly dated while the extensive basement remains roughly postulated by limited geophysical data.This study presents a systematic analysis including U-Pb geochronology,elemental geochemistry and petrographic identification on granite and meta-clastic borehole samples from several key areas.Constrained from gravity-magnetic joint inversion,this interpretation will be of great significance revealing the tectono-magmatic evolution along the southeastern margin of the Eurasian Plate.Beneath the thick Cenozoic sediments,the northern SCS is composed of a uniform Mesozoic basement while the Precambrian rocks are only constricted along the Red River Fault Zone.Further eastern part of the northern SCS below the Cenozoic succession was widely intruded by granites with Jurassic-to-early Cretaceous ages.Further western part,on the other hand,is represented by meta-sedimentary rocks with relatively sporadic granite complexes.To be noted,the western areas derived higher-degree and wider metamorphic zones,which is in contrast with the lowerdegree and narrower metamorphic belt developed in the eastern region.Drastic collisions between the Indochina Block and South China continent took place since at least late Triassic,resulting in large-scale suturing and deformation zones.At the westernmost part of the northern SCS,the intracontinental amalgamation with closure of the Meso-Tethys has caused fairly stronger and broader metamorphism.One metamorphic biotite granite is located on the suturing belt and yields a Precambrian U-Pb age.It likely represents the relict from the ancient Gondwana supercontinent or its fringes.Arc-continental collision between the Paleo-Pacific and the southeast China Block,on the other hand,results in a relatively narrow NE–SW trending metamorphic belt during the late Mesozoic.Within the overall geological setting,the Cenozoic SCS oceanic basin was subsequently generated from a series of rifting and faulting processes along the collisional-accretionary continental margin.展开更多
Dongsha Island and the adjacent sea area locate at the northern continental margin of the South China Sea (SCS), and is connected to the east by the Manila Trench. Analyses of seismic stratigraphy and gravity, magneti...Dongsha Island and the adjacent sea area locate at the northern continental margin of the South China Sea (SCS), and is connected to the east by the Manila Trench. Analyses of seismic stratigraphy and gravity, magnetic and drilling wells data led to the discovery of three post fault sequences (V, VI, VII). Extensive tectonic uplift, magma activity and erosion occurred in Dongsha Island and the adjacent area, where most of the faults in the northeastern SCS were still active during Pliocene and Quaternary. Two groups of faults trending NEE and NW were developed during Late Cenozoic. We conclude that three important tectonic movements, especially Dongsha movement (4.4-5.2 Ma) and Liuhua movement (1.4-1.89 Ma), controlled the structural framework in the Dongsha rise; whose deformation in the east is stronger than that in the west and whose stress field variation suggests that the tectonic uplift in the study area contributed to magmato tectonic events correlated to the main collision phases between the East China and Taiwan 5-3 and 3-0 Ma ago.展开更多
基金The National Natural Science Foundation of China under contract Nos 42076066,92055203 and 41874076the National Science and Technology Major Project under contract Nos 2016ZX05026004-002 and 2017ZX05026005-005the Fund of China Association for Science and Technology under contract No.2018CASRQNJL18
文摘The pre-Cenozoic northern South China Sea(SCS)Basin basement was supposed to exist as a complex of heterogeneous segments,divided by dozens of N-S faulting.Unfortunately,only the Hainan Island and the northeastern SCS region were modestly dated while the extensive basement remains roughly postulated by limited geophysical data.This study presents a systematic analysis including U-Pb geochronology,elemental geochemistry and petrographic identification on granite and meta-clastic borehole samples from several key areas.Constrained from gravity-magnetic joint inversion,this interpretation will be of great significance revealing the tectono-magmatic evolution along the southeastern margin of the Eurasian Plate.Beneath the thick Cenozoic sediments,the northern SCS is composed of a uniform Mesozoic basement while the Precambrian rocks are only constricted along the Red River Fault Zone.Further eastern part of the northern SCS below the Cenozoic succession was widely intruded by granites with Jurassic-to-early Cretaceous ages.Further western part,on the other hand,is represented by meta-sedimentary rocks with relatively sporadic granite complexes.To be noted,the western areas derived higher-degree and wider metamorphic zones,which is in contrast with the lowerdegree and narrower metamorphic belt developed in the eastern region.Drastic collisions between the Indochina Block and South China continent took place since at least late Triassic,resulting in large-scale suturing and deformation zones.At the westernmost part of the northern SCS,the intracontinental amalgamation with closure of the Meso-Tethys has caused fairly stronger and broader metamorphism.One metamorphic biotite granite is located on the suturing belt and yields a Precambrian U-Pb age.It likely represents the relict from the ancient Gondwana supercontinent or its fringes.Arc-continental collision between the Paleo-Pacific and the southeast China Block,on the other hand,results in a relatively narrow NE–SW trending metamorphic belt during the late Mesozoic.Within the overall geological setting,the Cenozoic SCS oceanic basin was subsequently generated from a series of rifting and faulting processes along the collisional-accretionary continental margin.
文摘Dongsha Island and the adjacent sea area locate at the northern continental margin of the South China Sea (SCS), and is connected to the east by the Manila Trench. Analyses of seismic stratigraphy and gravity, magnetic and drilling wells data led to the discovery of three post fault sequences (V, VI, VII). Extensive tectonic uplift, magma activity and erosion occurred in Dongsha Island and the adjacent area, where most of the faults in the northeastern SCS were still active during Pliocene and Quaternary. Two groups of faults trending NEE and NW were developed during Late Cenozoic. We conclude that three important tectonic movements, especially Dongsha movement (4.4-5.2 Ma) and Liuhua movement (1.4-1.89 Ma), controlled the structural framework in the Dongsha rise; whose deformation in the east is stronger than that in the west and whose stress field variation suggests that the tectonic uplift in the study area contributed to magmato tectonic events correlated to the main collision phases between the East China and Taiwan 5-3 and 3-0 Ma ago.
