岚山头一带含霓石碱长花岗岩的基本特征及其地质意义

BASIC CHARACTERISTICS AND GEOLOGICAL SIGNIFICANCE OF AEGIRINE-BEARING ALKALINE GRANITE IN LANSHANTOU

摘要:

岚山头一带含霓石碱长花岗岩分布在胶南造山带的南段，是华北板块与扬子板块碰撞晚期在引张环境下形成的A型花岗岩。该花岗岩含有霓石、钠闪石、微斜长石、钠长石等碱性矿物；K2O和Na2O的含量为8．4％～9．6％，H2O＋少于0．16％，具有富碱、贫水的特点；稀土元素总量在262．19×10－6～313．23×10－6范围内，87Sr／86Sr初始比值为0．72902；Pb－Pb同位素年龄值为622．7Ma。含霓石碱长花岗岩体内含有较多的柯石英榴辉岩、榴辉岩包体。柯石英榴辉岩为超高压变质作用的产物，而其围岩（含霓石碱长花岗岩）却保存下了岩浆成因的霓石，处于富Na、Al、Si变质环境中，未出现硬玉或硬玉分子较高的绿辉石。这说明含霓石碱长花岗岩没有经受过超高压变质作用，即柯石英榴辉岩相对其围岩而言是外来的。

Abstract:

The aegirine-bearing alkaline granite in Lanshantou is distributed in the south of the Jiaonan orogenic belt. It is A-type granite fomed in the extension environment of the late stage of the collision between the north China plate and the Yangtz plate. Alkaline minerals t such as aegirine, riebeckite, microcline and albite are found in it. The contents of K2O and Na2O range from 8. 4 %～9. 6 % , and H2O+is less than 0. 16 % ; thus,we can say it is rich in alkali and poor in water; the contents of LIL element...