摘要
本区高级片麻岩地体中有五种类型基性、超基性岩脉群。根据岩脉群及其围岩变质和变形特点,本文确定了早前寒武纪克拉通演化史中先后两个变质、变形旋回,即太古宙克拉通演化早期的高塑性变形和辉石麻粒岩相变质旋回和克拉通晚期变形和角门岩相—角闪麻粒岩相变质旋回。大规模岩脉群的侵入构成了克拉通晚期独立的构造—岩浆—变质事件,是克拉通造山运动结束的标志之一,并揭示了克拉通团结、稳定的过程。
Five varieties of basic and ultrabasic metamorphosed dyke swarms have been recognised in the high-grade gneiss terrain in Taipingzai region , East Hebei Province. They are Ⅰ. pyroxene-granulite dykes and amphibole-pyroxenite dykes intruded in per- or syn-D2 deformation phase and metamorphosed by pyroxenegranulite facies; Ⅱ.garnet amphibole anorthositic diopsidite dykes metamorphosed by high- grade amphibolite facies; Ⅲ. diabase-porphyrite dykes metamorphosed by amphibole- granulite facies;Ⅱ.amphibolite dykes metamorphosed by low-grade amphibolite facies andⅢ.diabase dykes metamorphosed by greenschist facies. The latter four types of dyke intruded in the ending of Archaean.According to the feature of deformation and metamorphism of dyke Ⅱ.Ⅲ. and Ⅳ., the author have determined D4 deformation phase in the early precambrian deformation history and high-grade amphibolitefacies to amphibole-granulite facies. This is a new tectonic-magmati-cmetamorphic event of crustal evolution. So, at least two granulite facies metamorphic events have taken place in this area.The intrusion of numerous dyke swarms is one of the marks of ending andstabilization of cratonic orogenic movement.The characteristics of dyke swarm reflected the evolution regularity that crustal temperature gradually lowered and deformation changed from ductile to brittle.
关键词
变质岩
脉群
冀东
早前寒武纪
metamorphosed dyke swarm, early Precambrian craton, East Hebei Province
