Progresses in the Study of Metamorphism of Northwest China in the Past Decade

The study of metamorphism plays an important role in deciphering the composition and evolution of the deep crust, restoring the thermal evolution history of the crust, and guiding the prospecting. Both ancient continental blocks and Phanerozoic orogenic belts in northwest China are the key areas for the study of metamorphism in China. This paper reviews ultra-high pressure (UHP) metamorphism, ultra-high temperature (UHT) metamorphism, crustal anatexis, fluid activity in subduction zone and metamorphic mineral prospecting in northwest China in the past decade. In terms of UHP metamorphism, based on the new discoveries of evidences of UHP metamorphism represented by coesite, the fact of deep subduction of rocks has been further strengthened for previously established UHP metamorphic belts, and the East Kunlun UHP metamorphic belt was firstly established. In terms of UHT metamorphism, progresses in P–T paths, metamorphic ages and genesis of UHT metamorphism have been achieved in the Altai and Altyn orogen, and new outcrops of UHT metamorphic rocks have been identified in the East Kunlun, Qinling orogens and western Qaidam. The study of partial melting has been the focus of the study of orogenic metamorphism in the past decade, mainly including the products of partial melting, the tectonic setting and mechanism of melting. Studies on fluid activities in subduction zones focus on fluid identification and composition characterization, which provide a basis for further study of mass transfer in subduction zones. New discoveries of metamorphic ore deposits, represented by rutile and crystalline graphite, have been made.