河北怀安地区花岗闪长质片麻岩地球化学特征及年代学研究

Zirconage and geochemistry of granodioritic gneissin in Huai'an,Hebei province

华北古陆的南北缘广泛分布着地球上目前已知年代最久远的早前寒武纪TTG岩系,其地球化学特征因起源和成因的不同存在较大差异;因此,对河北怀安地区花岗闪长质片麻岩开展地球化学分析和年代学的研究工作,对认识华北古陆地壳的演化、增生和再造具有重要意义。结果表明,花岗闪长质片麻岩的结晶年龄为2551 Ma,形成于新太古代五台旋回。岩体岩石类型主要为中细粒含紫苏花岗闪长质片麻岩,SiO_(2)含量介于67.30%~74.94%,平均70.94%,总碱度K2O+Na2O=5.57%~8.01%,平均6.37%,A/CNK平均1.53,属于偏铝质花岗岩。通过对该岩体构造环境分析,认为该花岗闪长质片麻岩主要形成于岩浆弧构造环境。

The northern and southern margin of the north China continent are widely distributed in the early Cambrian TTG system,which is the oldest known in the world.The geochemical characteristics of the early Cambrian rocks are quite different from the origins and Genesis.Therefore,it is of great significance to study the geochemical analysis Geochemical analysis and geochronology of granodioritic gneiss in Huai'an area,Hebei Province,and evolution,hyperplasia as well as reforger in the north China.The results show the LA-ICP-MS zircon U-Pb isotope concordia diagram age is 2551 Ma,indicated granodiorite rock body was formed in Early Paleoproterozoic Era.Granite.The intrusion is dominated by medium grained hypersthenes Granodioritic gneiss.Their SiO_(2) and total alkaline contents are in the ranges of 67.30%~74.94%(average 70.94%)and 5.57%~8.01%(average 6.37%),respectively.Most of rocks belong to peraluminous(average A/CNK=1.53)granite and generated in syncollisional setting.This intrusion is formed in a magmatic arc tectonic environment.