华南花岗岩暗色微粒包体的岩石化学组成特征及其意义

摘要

Inhomogeneous enclave is the most popular type in the marie microgranular enclave (MME) of gran ites in SE China, which is generally with a dark or more mafic tim. The lithologic units in the rim of MME range from monzonite to quartz monzonite and to monzodiorite, while those in the core from quartz monzodior ite to tonalite. A MME generally has decreasing Si and Ca contents and Na/K ratios, and increasing K, Al,Ti, P and Fe＋Mg contents from its core to rim, indicating that the MMEs should have been mainly derived from restites of the partial melting rock. Further research revealed that the composition of restite in granites varies in the direction of increasing biotite as the melting degree of the rock increases and the biotite-rich en claves should be the final product of rock melting process.%对华南诸多花岗岩体暗色微粒包体的野外调查表明, 非均一包体是包体中最普遍的类型,常具有暗色基性边.岩石化学分析结果表明,包体边缘的岩性为二长岩-石英二长岩-二长闪长岩,中心则为石英二长闪长岩-英云闪长岩.从包体中心到边缘,具有Si、Ca含量和Na/K比值降低,K、Al、Ti、P和Fe+Mg含量升高的变化趋势,揭示包体应来自岩石部分熔融的残余熔渣.进一步研究还表明,花岗岩中残余熔渣(暗色包体)的组分随着岩石熔融程度升高而向黑云母增多的方向演化,暗示富云包体应是岩石熔融演化至末阶段的产物.