P-T Path And Geological Significance Of Hiph-Pressure Mafic Granulites In Xuanhua,Hebei Province

High-pressure granulites are information carriers of deep crust,thus study of high-pressure granulites provides opportunities to understand the middle-lower crust component and the process of continental evolution.Xuanhua,Hebei province is one of the locations in which high-pressure granulites were reported for the first time in China,situated in the North margin of Trans North China Orogen.Here in this article mafic granulites in Dadonggou,Xuanhua were chosen to be study material and were identified to be high-pressure granulites,depending on petrographic observation.Three mineral assemlages were recorded from the two samples,the peak assemblage is Grt+Cpx+Pl+Q reaching high-pressure granulite facies,the decompressional assemblage is Cpx+Opx+Pl,representing the intermediate-pressure granulite facies,and the retrograde assemblage is Hbl+Pl,namely the amphibolite facies.P-T conditions calculated from thermal modeling are the following: garnet core,760 ±20 ?,11.2±0.5 kbar;mantle,860±10 ?,13.1±0.3 kbar and rim,920±10 ?,9.6±0.2 kbar.P-T path is clockwise type with additional prograde stage and thermal relaxation after peak comparing with previous studies,and the temperature calculated herein is higher.