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.