扬子地区古生代盆地构造格架和油气关系的若干初步认识

扬子地区古生代盆地(从青白口纪起)是在早中元古代陆壳内裂谷拉张的基础上发展起来的.盆地发展经历了晚元古代—早古生代和晚古生代一三叠纪早中期两大世代.本文简要分析了两个世代盆地格架,重点论述了第一世代围绕陆壳向外扩展离散而成的两类边缘、第二世代陆内拗陷和断陷,关于盆地形成,变形的动力学特征和迭加关系以及中新生代冲断活动对它们的迭加改造.提出了本区寻找油气的有利领域.

A VIEW ON TECTONICS OF PALEOZOIC BASINS OF THE YANGTZE REGION AND ITS IMPLICATION OF HYDROCARBONS

Regional investigation shows that the evolution of the Paleozoic basins on the Yangtze Craton experienced a primary extensional rifting in which smaller collage blocks with a great mobility and inhomogeneity were assembled during the end of middle Proterozoic and then the Paleozoic basins began to be disintegrated. The aulacogen in the north was of oceanicc rust and was later obliterated by the collision at the end of Silurian. Meanwhile rift-margin made up in the south was accreted with exotic collage blocks elavated. As a regional convergence, several cratonic depressions associated with occasional extensional rifting developed with the seawater invasion of Paleo-Tethys mainly from southwest in late Paleazoic. Some blocks separated from the southern craton during Carboniferous-Permian-late Triassic periods came into collision again.Consequently, the framework of Paleozoic basins were reformed as a result of intraplate deformation with crustal-stacking or delamination during Meso-Cenozoic, rifting to the collision of Paleo-Neo-Tethys and the effect of the Pacific Plate. As mentioned aboved, it is suggested that Paleozoic hydrocarbons were mainly generated from the present mountain belt, where the content of organic carbon is much more abundant than that carbonate platform. The subsidence in early Paleozoic perhaps played an important role in generation and migration of hydrocarbons before Caledonian. The napping may be favourable to the conservation of the generated hydrocarbons and the perspecting area could included some favourable belts such as the Foothills of Longmen and Daba mountains, and nor-thern fringe of the Xiafung-Jiannan Hill are worthy to be explored furthermore.