To understand the forming and tectonic evolution of the South China Sea basin, new data of the structural styles and geochronology were obtained from the Dulong-Song Chay dome, southeastern Yunnan and northern Vietnam...To understand the forming and tectonic evolution of the South China Sea basin, new data of the structural styles and geochronology were obtained from the Dulong-Song Chay dome, southeastern Yunnan and northern Vietnam. The structural styles were acquired through field investigation and geo-chronological dating was carried out using zircon SHRIMP Ⅱ U-P and argon isotopic analyses. The South China Sea basin extension occurred firstly at Late Mesozoic to Early Cenozoic, and then at Late Oligocene to Middle Miocene （32-17 Ma）. The second stage of extension formed immediately after the first stage, and both extensions have a consistent forming mechanism. New structural analysis and geo-chronological data do not support the models of ＂backarc spreading＂ and ＂strike-slip faults producing the extension＂. Then what mechanism resulted in the extension of South China Sea basin？ The data indicate that at least two episodes of major extensional tectonics, i.e. , the D1 deformation at 237-228 Ma resulted in the rising and exhumation of the dome, and D2 deformation at 86-78 Ma overprinted and redeformed the dome. Of them, the D2 shows a consistent forming time, extensional direction and tectonic regime among Dulong-Song Chay dome, South China block and the northern margin of the South China Sea basin. Regional geology has proved that the northern margin of the South China Sea basin belongs to the South China block, therefore, we interpreted that the Late Mesozoic to Early Cenozoic extensional tectonics occurred in the northern margin of the South China Sea basin due to the intraplate deformation of the South China block, while the Ailaoshan-Red River sinistral slip strengthened the Cenozoic extension in the South China Sea basin.展开更多
越南东北部-海南岛-粤西南构造带整体上呈NW-SE走向展布于华南板块的南缘,是理解华南构造演化的关键地区。作为印支运动代表性地区的越南东北部地区Song Chay构造带上,下古生界浅变质沉积岩、上古生界至早-中三叠世未变质的沉积盖层中...越南东北部-海南岛-粤西南构造带整体上呈NW-SE走向展布于华南板块的南缘,是理解华南构造演化的关键地区。作为印支运动代表性地区的越南东北部地区Song Chay构造带上,下古生界浅变质沉积岩、上古生界至早-中三叠世未变质的沉积盖层中都发育向北东逆冲推覆,韧性变形域表现为NE-SW向的矿物拉伸线理和上部指NE的剪切变形,而脆性变形域则记录了大量NE极性的褶皱和冲断构造。两广交界的云开地体和海南岛地区存在着相同样式的构造变形。关于这期变形的时间,本文通过对野外地层以及所出露不同时期岩体变形特征的综合研究,并结合高质量的锆石U-Pb年代学数据,在越南的东北部厘定为237～228Ma。这期广泛分布于华南板块南缘构造事件的动力学机制同Day Nui Con Voi(大象山)微陆块与华南板块在早中生代的构造拼合事件相关。本文认为华南板块在早三叠世开始沿着越南东北部的Song Chay缝合带俯冲拼合于Day Nui Con Voi微陆块之下,因此在早-中三叠世时期,在作为俯冲盘的华南板块南缘发育一系列的褶皱和逆冲推覆构造,晚三叠世印支造山作用结束。因此,华南板块南缘的越南东北部-海南岛-粤西南构造带被一同卷入早-中三叠世同印支板块的碰撞造山体系之中。展开更多
文摘To understand the forming and tectonic evolution of the South China Sea basin, new data of the structural styles and geochronology were obtained from the Dulong-Song Chay dome, southeastern Yunnan and northern Vietnam. The structural styles were acquired through field investigation and geo-chronological dating was carried out using zircon SHRIMP Ⅱ U-P and argon isotopic analyses. The South China Sea basin extension occurred firstly at Late Mesozoic to Early Cenozoic, and then at Late Oligocene to Middle Miocene （32-17 Ma）. The second stage of extension formed immediately after the first stage, and both extensions have a consistent forming mechanism. New structural analysis and geo-chronological data do not support the models of ＂backarc spreading＂ and ＂strike-slip faults producing the extension＂. Then what mechanism resulted in the extension of South China Sea basin？ The data indicate that at least two episodes of major extensional tectonics, i.e. , the D1 deformation at 237-228 Ma resulted in the rising and exhumation of the dome, and D2 deformation at 86-78 Ma overprinted and redeformed the dome. Of them, the D2 shows a consistent forming time, extensional direction and tectonic regime among Dulong-Song Chay dome, South China block and the northern margin of the South China Sea basin. Regional geology has proved that the northern margin of the South China Sea basin belongs to the South China block, therefore, we interpreted that the Late Mesozoic to Early Cenozoic extensional tectonics occurred in the northern margin of the South China Sea basin due to the intraplate deformation of the South China block, while the Ailaoshan-Red River sinistral slip strengthened the Cenozoic extension in the South China Sea basin.
文摘越南东北部-海南岛-粤西南构造带整体上呈NW-SE走向展布于华南板块的南缘,是理解华南构造演化的关键地区。作为印支运动代表性地区的越南东北部地区Song Chay构造带上,下古生界浅变质沉积岩、上古生界至早-中三叠世未变质的沉积盖层中都发育向北东逆冲推覆,韧性变形域表现为NE-SW向的矿物拉伸线理和上部指NE的剪切变形,而脆性变形域则记录了大量NE极性的褶皱和冲断构造。两广交界的云开地体和海南岛地区存在着相同样式的构造变形。关于这期变形的时间,本文通过对野外地层以及所出露不同时期岩体变形特征的综合研究,并结合高质量的锆石U-Pb年代学数据,在越南的东北部厘定为237～228Ma。这期广泛分布于华南板块南缘构造事件的动力学机制同Day Nui Con Voi(大象山)微陆块与华南板块在早中生代的构造拼合事件相关。本文认为华南板块在早三叠世开始沿着越南东北部的Song Chay缝合带俯冲拼合于Day Nui Con Voi微陆块之下,因此在早-中三叠世时期,在作为俯冲盘的华南板块南缘发育一系列的褶皱和逆冲推覆构造,晚三叠世印支造山作用结束。因此,华南板块南缘的越南东北部-海南岛-粤西南构造带被一同卷入早-中三叠世同印支板块的碰撞造山体系之中。
