关键词: 中下扬子区, 古生代盆地, 陆内俯冲, 陆壳挤压, 基底拆离, 盖层滑脱

Abstract:

The Indo-China movement derived from the closure of the Tethys resulted in sub-duction of the Yangtze and North China Platforms to Dabie-Jiaonan Orogenic Belts. The polyphase and multilayer basement detaching and thrust-nappe of Qinling-Dabie-Jiaonan Orogenic Belts resulted in super-imposition of a series of nappe sheets in different grades,different scales and different deformation intensities, which was the main tectonic style for the formation of the orogenic belts. The orogenic belts then obducted to the Yangtze and North China Platforms with the displacement of 20-40km respectively during late Yen-shanian. In the process of the northward subduction, the Yangtze Platform itself had been experienced the reformation dominated by basement detaching and multilayer decollement of caprocks. The NE,/i>-near EW trend Sichuan, Hubei, Hunan, Guizhou-Jiangsu, South Anhui frontal folding-thrusting belt which formed under the northward compression-overthrusting of the Jiangnan-Xuefeng basement detaching napping-uplift belt was super-imposed and further reformed by the NW-near EW trend foreland folded-thrust belt caused by the southward obduction and thrusting-compression of the Qingling-Dabie-Jiaonan Orogenic Belts. Finally, the tectonic framework of opposite thrusting formed at both the south and north sides of the Yangtze Platform. The main trap types for hydrocarbon accumulation may occur at the following places:the trailing adge of basement detaching-thrusting uplift belt, the decollement folds at the faulted flat overlain by gliding nappes, X-type joint groups at footwall ramp, the fault-extending-decollement folding superimposed by Meso-Cenozoic fault-depressed basins within the faulted flat of lower thrusting sheet, the monadnock on ancient erosive surface, the mixed folds of high and duplex thrust structures at blind thrusted front.