对三塘湖盆地基底的认识

AN UNDERSTANDING OF THE BASEMENT OF SANTANGHU BASES.

根据三塘湖盆地区域构造及重力、磁力、电性特征,提出了盆地基底有双重结构的看法,深层基底是由前寒武纪古老结晶基底与西部另一地体或陆缘碎块及洋壳残片的拼接而成,之后又叠加了以海西期火成岩为主的浅层褶皱基底.基底结构的这种双重性明显影响着盖层的构造特征;盆地东部由于存在深层刚性基底,抑制了盖层的后期构造变形,在盖层中往往形成大面积的宽缓的构造圈闭;盆地西部由于不具刚性基底,盖层中往往形成线性褶皱和断阶、断块;现今的构造格局基本受控于浅层(下石炭统)基底.

This paper gives an idea that the basement of Santanghu basin has a dual structure by combining the regional structures with the gravity, magnetic and electrical property data in the basin. The deeper basement formed as the Pre-Cambrian crystallized basement segmented with the another land mass in the west or continental marginal residual plates and fragments of ocean crust, and then was superimposed with the shallower folded basement dominated by Hercynian igneous rocks. Such dual nature significantly affected the characteristic of seal structure. In the east the later structural deformation of the seal is inhibited due to the presence of deeper rigid basement, which resultecd in the formation of extensive wide and gently dipping traps in the caprock; while in the west the linear folds, fault terrace and blocks formed in the caprock due to the absence of the rigid basement. The present tectonic framework is almost controlled by the shallower (Lower Carboniferous) basement.