新疆前震旦纪地层划分及地壳演化

STRATIGRAPHIC DIVISION AND CRUSTAL EVOLUTION OF PRE-SINIAN IN XINJIANG

根据变质地质学的观点,新疆的前震旦纪地层可划分为太古界、下元古界和中一上无古界,它们在岩石组合、原岩建造、变质作用类型及形成环境等方面具有明显的区别,同时表明古西北陆台具有与古华北陆台完全不同的地质发展历史。

The pre-Sinian strata are divided into Archaean, early Proterozoic and middle-late Proterozoic in Xinjiaag. The Archaean crops out only in Altun Mountain. It is composed of rocks of granulite facies and amphibolite facies. The early Proterozoic is widely distributed in the southern region of Junggar Basin. It is mainly represented by low-or medium pressure facies series with amphibolite facies in dominance among the progressive metamorphic zones. The metamorphism is of regional dynamic heat flow type. Migmatites are well developed. The middle-late Proterozoic includes the Chaagcheng, Jixian and Qisabaikou Groups. The metamorphism is of regional low temperature dynamic type with low greenschist facies in dominance. Stromatolites are abundant. These distinct the crustal evolution of the old Northwestern China Platform from the old North China Platform.