大别山杂岩中两类斜长角闪岩的矿物学鉴别标志及对榴辉岩成因的意义

IDENTIFICATION MARKS OF AMPHIBOLITE RETROGRADED FROM ECLOGITE AND ORDINARY AMPHIBOLITE FROM THE DABIE MOUNTAINS: IMPLICATIONS FOR THE GENESIS OF ECLOGITE

鉴别造山带斜长角闪岩由含柯石英榴辉岩退变而成，还是未经过超高压变质作用的普通斜长角闪岩，对研究榴辉岩成因有重要意义。本文提出用斜长角闪岩中两个最常见矿物，石榴子石和角闪石的Mno和Mgo含量以及四次配位Al和六次配位Al数可有效地区分这两种不同成因的斜长角闪岩。本文提供的数据表明：大别群变质杂岩中有一部分斜长角闪岩并未经历过超高压变质作用。因此，大别群中的超高压变质岩是构造侵入到角闪岩相岩石中的产物。

It is of great importance for revealing the genesis of orogenic eclogite to identify whether plaioclase amphibolite occurring in an orogenic belt was retograded from eclogite or is ordinary one.This paper suggests that in terms of MnO and MgO contents in garnet and Al and Al numbers in mphibole, which are two common minerals in amphibolite, the above two kinds of amphibolite can e classified. The data presented in this paper suggest that part of the amphibolite in the Dabie letamorphic complex has not experienced ultrahigh-pressure metamorphism. There fore, the ultrahigh-pressure metamorphic rocks in the Dabie Mountains, such as coesite-bearing eclogite,were tectonically emplaced into the amphibolite-facies metamorphic rocks.