The New Progress in the Study of Mesozoic Tectonics of South China
Mesozoic tectonic regime underwent the transform from the Meso-Tethyan tectonic domain to the west Pacific tectonic domain, which caused intense intraplate orogenesis and magmatism in South China, forming a wide and complex intracontinental orogen and igneous province in this region of East Asia. Some progresses have been achieved recently in the study of this Mesozoic tectonics of South China, which are summarized as follows:(1) On the basis of field analysis of fault kinematics affecting different lithostratigraphic units of the Yuanma basin in central South China, a five-stage tectonic stress evolution history from Late Mesozoic to Early Cenozoic period was established, which included Middle-Late Jurassic E-W compression, Early Cretaceous NW-SE extension, Early Cretaceous NW-SE compression, Late Cretaceous N-S extension and Paleogene NE-SW compression. The change in tectonic stress directions was interpreted in terms of the change either in plate tectonic settings or in deep-seated crustal process. (2) Superposed folds involving Late Paleozoic to Mesozoic strata in Hunan Province were recognized; it is considered that these cross folds might record the effects of plate boundary tectonics, i.e., the earlier W-E to WNW-ESE trending folds were formed in response to the Triassic collision of the South China Block with the North China Block and the Indochina Block, and the late NE to NNE trending folds were generated as the far-field effect of a low angle subduction of the Paleo-Pacific oceanic plate beneath the South China Block, which occurred in Mid-Late Jurassic. (3) The Hengshan metamorphic core complex was determined on the basis of detailed field investigation of a normal detachment fault zone developed along the western margin. SHRIPM U-Pb dating of zircons from strongly sheared albite made sure that the normal faulting was initiated in Early Cretaceous, at about 137 Ma. (4) Field observations and U-Pb dating of zircons revealed that the Changle-Nan'ao tectonic zone along the coast of southeast China corresponds to a Late Mesozoic orogenic zone formed in Late Jurassic to Early Cretaceous; it was materialized by gneissic granites, migmatites and amphibolite fades metamorphic rocks, which were dated to be 147-135 Ma. This orogenic zone began to collapse in 135-117 Ma, characterized by fine-grained granites. Based on the above results, this paper discusses the manifestations and plate tectonic backgrounds of the Indosinian and Yanshanman movements, and the time of the change from the compressive tectonic regime to the extensional region in Early Cretaceous.
intra-continental orogenesistectonic stress fieldcross foldsMesozoic tectonics change in tectonic regimeYuanma basinChangle-Nan'ao tectonic zoneSouth China
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维普
