胶东东部地区元古宙花岗岩类的地球化学及岩石成因

Geochemistry and Petrogenesis of the Proterozoic Granitoids in the East Shandong Peninsula,China

胶东东部地区的元古宙花岗岩－片麻岩杂岩，可分为：（１）石英闪长质－英云闪长质－花岗闪长质片麻岩、（２）二长花岗质－钾长花岗质片麻岩和（３）淡色花岗岩三套岩石。它们之间可识别侵位先后关系，岩相中普遍存在残留的斜长石板状晶体、并具环带结构为主的原生深成岩的矿物相组构，地球化学成分演化各具独立性，并具有深熔花岗岩的性质，结合同位素年龄资料，确立它们是元古宙不同造山阶段形成的花岗岩。岩石中普遍存在Ｔｉ、Ｙ、Ｓｒ、Ｎｉ及Ｍｇ等元素的强烈亏损，表明岩浆来源并非直接来源于上地幔或下地壳，它们是元古宙不同阶段已形成的岩石发生深熔作用形成的。这一认识有助于了解华北地台南缘东段元古宙这一重要地质时期的地壳形成和演化。

The granite gneiss complex in eastern Jiaodong peninsula can be divided into three kinds of lithologies, i.e.(1) quartz dioritic tonalitic granodioritic gneiss,(2)adamellitic granitic gneiss; and (3)leucocratic granite.The intrusion sequences among them can be identified and the tabular zoned plagioclase crystals,belonging to plutonic mineral fabrics are widely preserved in the intrusions.The geochemistry of the different lithologies shows the features of independent evolution and the characteristics of anatectic granites. Combined with isotopic ages,it has been determined that they are the granites formed during different stages of Proterozoic orageny.These rocks are commonly intensively depleted in Ti, Y, Sr, Ni, Mg, etc.,which proves that the magma was not directly derived from upper mantle or lower crust and they were the products of the anatexis of rocks that were formed in different stages of Proterozoic. This conclusion is very helpful to understand the Proterozoic crustal formation and evolution mechanism of the east sector of the south margin of North China platform.