冀东地区变质基性岩墙群的基本特征

MAJOR CHARACTERISTICS OF METAMORPHOSED BASIC DYKE SWARMS, EASTERN HEBEI PROVINCE

本文对冀东变质岩系中变质基性岩墙群的变质级、矿物组合、岩石组构、岩石化学特征及野外产状等作了介绍,对它们的生成时代、成因作了初步分析,并对它们在冀东太古代地质历史演化中的作用作了简要说明。

There are four kinds of metamorphesed basic dykes in the Early Precambrian metamorphic series, Eastern Hebei Province.1. Granulite, consists of basic plagioclast, hypersthene, diopside, and minor hornblende and biotite, without any nelicts of the original minerals and fabrics. They streteh in NW direction in the granulite-facies terrain composed of the Qianxi Group, end usually cut the gneissic schistosity of the country rock but being deformed synchronously with the letter.2. Garnet diopside amphibolite, mainly composed of acidic plagioclase, hornblende and diopside almandine and some quartz and biotite. Their protolithic mineral phases and fabrics had disappeared and are characterized by finegrained granoblastic texture. They are found in the upper succession of the Qianxi Group in the western part of this region and stretch in NE direction. Dykes of this kind often cut the gneissic schistosity of the country rock and retain clearly their chilling border texture being intrusive bodies.3. Amphibolite, chiefly consists of acidic plagioclase and hornblende with blasto-hypidiomorphic, blastoporphyritic texture and chilling border. They stretch in NE direction and are found in the metamorphic series of Dantazi Group and Zhuzhangzi Group in this region.4. Meta-diabasc with blasto-diabasic or blasto-porpyritic textures and a composition of labradorite, diopside, almandine, hornblende, biotite, some hyper-stheme and quartz. They are seen in Sh Shuichang and Taipingzhai distretch nearly S-N or E-W.The development of these different kinds of metamorphosed basic swarms in the region reflects there had been polyepisodic magmatism and regional metamor-phism in early Precambrian.A futher repearch on the metamorphosed basic dykes will give important clue TO the understanding of the crustal evolution, palaeo-voleanism and metamorphism of the related Easier Hebei province.