陕西汉阴北部梅子垭组变质作用研究

梅子垭组是汉阴北部地区出露面积最大的地层,岩性主要为白云母石英片岩、含碳白云母石英片岩、含石榴子石黑云母变斑晶白云母石英片岩等,石榴子石和黑云母变斑晶在该岩层中普遍发育。该岩组构造变形复杂,经历了多期构造活动和变质变形过程。笔者在野外调查的基础上,通过分析研究区石榴子石、黑云母变斑晶的关系,采用石榴子石-黑云母地质温度计,对该区广泛出露的含石榴子石黑云母变斑晶白云母石英片岩进行研究,得到如下结论:研究区存在3期黑云母和石榴子石,石榴子石变斑晶具有明显的生长环带,而黑云母变斑晶没有环带;研究区变质作用的变质温度范围为介于511~572℃,主要为530~560℃;变质压力范围为0.16~0.84GPa,变质相属高绿片岩相。

Metamorphism of the Meiziya Formation in Northern Hanyin,Shaanxi Province

The Meiziya Formation is the biggeststratum exposed in northern Hanyin, which is mainly composed of muscovite-quartz schist, carbon-containing muscovite-quartz schist, and muscovite-quartz schistwith garnet-bearing biotitemeta crystal. Garnet and biotite are widely developed in thisrock stratum. The formation and metamorphism of Meiziya Formation is complex, which has experienced a number of tectonic activity, metamorphism and deformation processes. Based on the field investigation, the relationship between garnet and biotite metacrystal has been analyzed and researched.Using garnet-biotite geothermometer, the widely exposed muscovite-quartz schist with garnet-bearing biotite metacrystal has been studied in this paper. The results show that three periods of biotite and garnet were developed in this studying area, the garnet porphyroblast has obvious growth zoning, but the biotite without any growth zoning. For this studying area, the metamorphic temperatures range from 511 to 572℃, most of them change from 530 to 560℃. Their metamorphicpressures vary from 0.16 to 0.84GPa, and their metamorphic event mainly corresponds to high greenschistface.