中国蓝闪石片岩带的一般特征及其分布

THE GENERAL FEATURES AND DISTRIBUTIONS OF THE GLAUCOPHANE SCHIST BELTS OF CHINA

蓝闪石片岩相可依据其温度划分为蓝闪石-硬柱石和蓝闪石-绿片岩相区,并与一些变质相组成不同相系。中国蓝闪石片岩带根据其平均温度-压力梯度和构造地质环境可分为:(1)元古代克拉通内蓝闪石片岩带;(2)加里东期克拉通内裂谷型蓝闪石片岩带;(3)古生代中国陆台北缘蓝闪石片岩带;(4)中新生代与俯冲作用有关的蓝闪石片岩带。蓝闪石变质作用的形成和演化与构造地质环境有关。中国蓝闪石片岩带大部分形成于硅铝壳环境,从陆壳开始裂开,直至出现洋壳。这一演化与地壳内热流变化格局有关,形成机理不属于均变论的观点。

On the basis of the temperature variation the glaucophane schist facies may be classified into two facies groups, the glaucophane-lawsonite and the gaucophane-greenschist facies groups, and forms various facies series with other metamorphic facies to reflect the imposed temperature-pressure gradient. Glaucophane schist belts of China are of different types with regard to their average temperature-pressure gradient and tectonic environment. They are: (1) Proterozoic glaucophane schist belts within the ancient craton, (2) Caledonian intra-cratonic glaucophane schist belts, (3) Palaeo- zoic per-cratonic glaucophane schist belts along the northern margin of the China Platform, and (4) Mesozoic-Cenozoic glaucophane schist belts related to recent subduction.The glaucophane schist metamorphism may occur and develop under different tectonic conditions. Most glaucophane schist belts of China are likely to be formed in ensialic environments. First the crust began to rupture and eventually oceanic crust was formed. A non-uniformitarian mechanism may be involved as this evolution is related to the change of the configuration of the heat flow within the crust.