The Characteristics Of Proterozoic Metamorphic Rock In Alatengaobao Area Of Alxa, Inner Mongolia

The proterozoic metamorphic rock as study objects of this paper which locate in north-western North China plate, where in Alatengaobao region of Alxa Youqi, Inner Mongolia.High greenschist facies and low amphibolites facies which are main metamorphic facies. The proterozoic metamorphic rock is concerned to form in mid-temperature and low-pressure according to metamorphic minerals association. The main type of metamorphism is regional metamorphism, partly dynamic metamorphism.Metamorphic plutonitic rocks in this area which are divided two parts, Bijiertai gneiss and Dabusushan gneiss. Biotite plagio-gneiss, amphibole biotite plagio-gneiss, two-mica two-feldspar gneiss are main rock types, primary rocks are quartz diorite, granodiorite, granite and so on. The temperature and pressure of metamorphism is 700-800℃, 0.20 GPa, tectonic background which belongs to plate pre-collision and syn-collision activity continental margin.Metamorphic supracrustal rocks are divided three parts, Hawala formation, Derhetongte formation and Zuzongmaodao formation. Two-mica quartz schist, two-mica two-feldspar gneiss, plagio-granulite, marble are main rock types, primary rocks are sediment-volcanic series. The temperature and pressure of metamorphism is 450-600℃, 0.60 GPa.The metamorphism in study area is possibly involved with the rift basin closing which occurred in northern north China plate from Mesoproterozoic to Neoproterozoic.