A total of 312 oriented core samples collected from the Neoproterozoic to lower Cambrian strata in the Lushan region of western Henan Province, southern North China Block, were subjected to stepwise demagnetization. A...A total of 312 oriented core samples collected from the Neoproterozoic to lower Cambrian strata in the Lushan region of western Henan Province, southern North China Block, were subjected to stepwise demagnetization. After removing recent and possibly Mesozoic overprint components, inferred primary magnetic remanence was isolated from the Precambrian Dongjia, Sanjiaotang and Cuizhuang Formations. Our new results, together with selected previous results, suggest that the North China Block was in low latitudinal positions for most of the studied time interval. Through comparison with paleogeographic positions of other continents, we suggest that the NCB could have been closed to Siberia during the ca. 800-600 Ma interval.展开更多
Affected by thermal perturbation due to mantle uprising, the rheological structure of the lithosphere could be modified, which could lead to different rifting patterns from shelf to slope in a passive continental marg...Affected by thermal perturbation due to mantle uprising, the rheological structure of the lithosphere could be modified, which could lead to different rifting patterns from shelf to slope in a passive continental margin. From the observed deformation style on the northern South China Sea and analogue modeling experiments, we find that the rift zone located on the shelf is characterized by half grabens or simple grabens controlled mainly by long faults with large vertical offset, supposed to be formed with normal lithosphere extension. On the slope, where the lithosphere is very hot due to mantle upweUing and heating, composite grabens composed of symmetric grabens developed. The boundary and inner faults are all short with small vertical offset. Between the zones with very hot and normal lithosphere, composite half grabens composed of half grabens or asymmetric grabens formed, whose boundary faults are long with large vertical offset, while the inner faults are relatively short. Along with the thickness decrease of the brittle upper crust due to high temperature, the deformation becomes more sensitive to the shape of a pre-existing weakness zone and shows orientation variation along strike. When there was a bend in the pre-existing weakness zone, and the basal plate was pulled by a clockwise rotating stress, the strongest deformation always occurs along the middle segment and at the transition area from the middle to the eastern segments, which contributes to a hotter lithosphere in the middle segment, where the Baiyun （白云） sag formed.展开更多
文摘A total of 312 oriented core samples collected from the Neoproterozoic to lower Cambrian strata in the Lushan region of western Henan Province, southern North China Block, were subjected to stepwise demagnetization. After removing recent and possibly Mesozoic overprint components, inferred primary magnetic remanence was isolated from the Precambrian Dongjia, Sanjiaotang and Cuizhuang Formations. Our new results, together with selected previous results, suggest that the North China Block was in low latitudinal positions for most of the studied time interval. Through comparison with paleogeographic positions of other continents, we suggest that the NCB could have been closed to Siberia during the ca. 800-600 Ma interval.
基金supported by the National Basic Research Pro-gram of China (Nos. 2009CB219401, 2007CB41170405)the CAS Key Innovation Program (No. KZCX3-SW-234-1)+2 种基金the National Natural Science Foundation of China (Nos. 40876026, 40576027)the Knowledge Innovation Program of the South China Sea Institute of Oceanology, CAS (No. LYQY200704)the Open Fund of the Key Laboratory of Marine Geology and Environment, CAS
文摘Affected by thermal perturbation due to mantle uprising, the rheological structure of the lithosphere could be modified, which could lead to different rifting patterns from shelf to slope in a passive continental margin. From the observed deformation style on the northern South China Sea and analogue modeling experiments, we find that the rift zone located on the shelf is characterized by half grabens or simple grabens controlled mainly by long faults with large vertical offset, supposed to be formed with normal lithosphere extension. On the slope, where the lithosphere is very hot due to mantle upweUing and heating, composite grabens composed of symmetric grabens developed. The boundary and inner faults are all short with small vertical offset. Between the zones with very hot and normal lithosphere, composite half grabens composed of half grabens or asymmetric grabens formed, whose boundary faults are long with large vertical offset, while the inner faults are relatively short. Along with the thickness decrease of the brittle upper crust due to high temperature, the deformation becomes more sensitive to the shape of a pre-existing weakness zone and shows orientation variation along strike. When there was a bend in the pre-existing weakness zone, and the basal plate was pulled by a clockwise rotating stress, the strongest deformation always occurs along the middle segment and at the transition area from the middle to the eastern segments, which contributes to a hotter lithosphere in the middle segment, where the Baiyun （白云） sag formed.
