论文部分内容阅读
在胶东地区莱西－莱阳－栖霞一带的晚太古代花岗片麻岩中，出露一条长约２００多公里，ＮＥ向展布的高压基性麻粒岩－超镁铁质岩带。由于这条岩带东邻苏鲁高压－超高压变质带，西接华北克拉通基底的古老变质岩，因此其区域构造归属以及大地构造意义是一个十分重要的问题。本文分析的高压基性麻粒岩样品具有降压退变质结构，退变质矿物组合为麻粒岩相。矿物－全岩Ｓｍ－Ｎｄ等时线年龄为１７５２Ｍａ，全岩Ｔ（ＤＭ）模式年龄为２７８８Ｍａ，与华北克拉通北缘的高压基性麻粒岩的同位素年龄完全相似。根据高压麻粒岩－超镁铁质岩的围岩片麻岩特征和同位素年龄，可以确定这条出露于华北陆块东缘的岩带是早前寒武纪华北克拉通下地壳岩石，其抬升与华北陆块与扬子陆块的拼合有关。
Late Paleoproterozoic granitic gneisses in the Laxi-Laiyang-Qixia area of the Jiaodong area show a high-pressure granulite-ultramafic belt that stretches more than 200 km long and NE-directionally. Due to the fact that the belt is adjacent to the Sulu HP-UHPM metamorphic belt in the east and the ancient metamorphic rocks in the base of the North China Craton, the significance of regional tectonics and geotectonic significance is a very important issue. The samples of high-pressure basic granulites analyzed in this paper have a buck-degenerate metamorphic structure and the metamorphic mineral assemblage is a granulite facies. The Sm-Nd isochron age of the mineral-whole rock is 1752 Ma, and the T (DM) model age of the whole rock is 2788 Ma, which is completely similar to the isotopic ages of the high-pressure basic granulites in the northern margin of the North China Craton. According to the characteristics of the gneisses and isotopic ages of the high-pressure granulite-ultramafic rocks, it can be concluded that the lithosphere exposed to the eastern margin of the North China block is the Lower Precambrian crust in the Lower North China Craton, Its uplift is related to the combination of the North China land mass and the Yangtze land mass.