THE COMPOSITIONAL ZONING OF GARNET OF PRECAMBRIAN KHONDALITE SERIES AND ITS APPLICATION TO TEMPERATURE-PRESSURE ESTIMATION IN ZHUOZI, INNER MONGOLIA
Liu Fulai(Department of Applied Geochemistry)
Mg,of garnet display an evident composition zoning feature inprecambrian Khondalite series in Zhuozi area. According to the genetic characteristics,they are divided into tvvo types of compositional zoning,the growth zoning and diffusivezoning. The growth zoning reflectsd the process of crystallization and growth of garnet,while the diffusive zoning responds to diffusion between garnet and biotite at the post-peak cooling stage. Granitic magmatism deeply influences the compositional zoning ofgarnet,which not only causes garnets being assenbled together,but also produces newgrowth zoning surrounding the rim of assemblage, With the help of garnet- biotitegeothermometer-barometer,as wellas different genetic types of compositional zoning ingarnet the peak-stage and post-peak cooling stage metamorphic temperature-pressureconditions could be determined.