Based on gravity data processed with the matched filter, depth continuation and horizontal gradient we obtained the spatial distribution of the gravity field and made analyses of the tectonic framework of South China....Based on gravity data processed with the matched filter, depth continuation and horizontal gradient we obtained the spatial distribution of the gravity field and made analyses of the tectonic framework of South China. Then, inversion was conducted for the depth to study the depth variation of the boundary between the crust and upper mantle, namely the Mohorovicic discontinuity (Moho). The results demonstrate that the Moho depth in South China ranges from 30 to 40 km, and the crust thins from west to east, 27-29 km under the continent margin and shallow sea. We think it possible that the Tanlu fault crosses the Yangtze River and extends southwards along the Ganjiang and Wuchuan-Sihui faults to the South China Sea, and that there is an E-W hidden structural belt along 24.5°-26°.展开更多
Guangdong Province in the central Cathaysian Block has two world-class metallogenic belts, namely, the Nanling and Southeastern Coastal Metallogenic Belts(NLMB and SCMB), which are spatially coincide with the major re...Guangdong Province in the central Cathaysian Block has two world-class metallogenic belts, namely, the Nanling and Southeastern Coastal Metallogenic Belts(NLMB and SCMB), which are spatially coincide with the major regional Ganjiang and Zhenghe-Dapu Fault Zones(GJFZ and ZDFZ). However, what roles the faults played in mineral deposition and magmatism is unclear. Using ambient noise tomography, we obtain a 3-D whole-crust shear wave velocity model. By combining available regional geophysical models, we characterize the architecture of the regional shallow lithosphere and infer its possible tectonic connection to magmatic sources, pathways and surface deposition. The results show that the study area is loosely divided by the two major faults, the GJFZ and ZDFZ, into distinct velocity domains. In the north high Vand low V/Vcrust in the NLMB imply crustal remelting, which leads to the general felsic composition. In the coastal area, the lower crustal high Vanomaly is attributed to upwelling melts associated with Cretaceous magmatic activity. Between mineral belts, a swath of crustal lowvelocity zones extend into the uppermost mantle, manifesting partial melting related to upwelling magmas that may hint at a deep origin of magma from subcrustal lithosphere and likely feed surface mineral deposits through major faults. Secondary NW-trending faults coincide with low velocities and facilitated magmatic migration. A correlation between coastward extension of low velocities and younging of the Jurassic and Cretaceous magmatism is suggestive of a combined effect of slab rollback and a change in the direction of the Paleo-Pacific subduction system. We speculate a regional fault-control model in the central Cathaysian Block for the spatial-temporal evolution of regional deformation and magmatism during the middle Mesozoic.展开更多
基金Th is study was carried out during 2001-2003 and financially supposed by the National Natural Science Foundation of China(No.40074020)
文摘Based on gravity data processed with the matched filter, depth continuation and horizontal gradient we obtained the spatial distribution of the gravity field and made analyses of the tectonic framework of South China. Then, inversion was conducted for the depth to study the depth variation of the boundary between the crust and upper mantle, namely the Mohorovicic discontinuity (Moho). The results demonstrate that the Moho depth in South China ranges from 30 to 40 km, and the crust thins from west to east, 27-29 km under the continent margin and shallow sea. We think it possible that the Tanlu fault crosses the Yangtze River and extends southwards along the Ganjiang and Wuchuan-Sihui faults to the South China Sea, and that there is an E-W hidden structural belt along 24.5°-26°.
基金supported by the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou) (Grant No. GML2019ZD0204)the National Natural Science Foundation of China (Grant Nos. 42076068, 91858212, 41730532, 91958212, 91955210)。
文摘Guangdong Province in the central Cathaysian Block has two world-class metallogenic belts, namely, the Nanling and Southeastern Coastal Metallogenic Belts(NLMB and SCMB), which are spatially coincide with the major regional Ganjiang and Zhenghe-Dapu Fault Zones(GJFZ and ZDFZ). However, what roles the faults played in mineral deposition and magmatism is unclear. Using ambient noise tomography, we obtain a 3-D whole-crust shear wave velocity model. By combining available regional geophysical models, we characterize the architecture of the regional shallow lithosphere and infer its possible tectonic connection to magmatic sources, pathways and surface deposition. The results show that the study area is loosely divided by the two major faults, the GJFZ and ZDFZ, into distinct velocity domains. In the north high Vand low V/Vcrust in the NLMB imply crustal remelting, which leads to the general felsic composition. In the coastal area, the lower crustal high Vanomaly is attributed to upwelling melts associated with Cretaceous magmatic activity. Between mineral belts, a swath of crustal lowvelocity zones extend into the uppermost mantle, manifesting partial melting related to upwelling magmas that may hint at a deep origin of magma from subcrustal lithosphere and likely feed surface mineral deposits through major faults. Secondary NW-trending faults coincide with low velocities and facilitated magmatic migration. A correlation between coastward extension of low velocities and younging of the Jurassic and Cretaceous magmatism is suggestive of a combined effect of slab rollback and a change in the direction of the Paleo-Pacific subduction system. We speculate a regional fault-control model in the central Cathaysian Block for the spatial-temporal evolution of regional deformation and magmatism during the middle Mesozoic.
