Metamorphic Evolution and Zircon U-Pb Ages of the Nanshankou Mafic High Pressure Granulites from the Jiaobei Terrane, North China Craton

摘要: Petrological analysis and LA-ICP-MS zircon U-Pb dating were conducted on high-pressure mafic granulites, which occured as xenolith within TTG gneisses, from the Nanshankou Village of Jiaobei terrane, Shandong Peninsula in north-eastern part North China Craton (NCC). The HP granulite is composed garnet, clinopyroxene, orthopyroxene, amphibole symplectitic plagioclase, ilmente magnetite formed after decomposition porphyroblastic garnet clinopyroxene. Four stages metamorphic mineral assemblages for granulites constrained by detail petrological mineralogical investigations. early prograde assemblage represented inclusions clinopyroxene porphyroblasts (Opx1+Pl1+Qtz1), recording conditions at ~754–757 °C, 0.63–0.71 GPa; peak determined ~874–891 1.32–1.35 GPa with Grt2+Cpx2+Amp2+Pl2+Qtz2. Retrograde minerals derived Opx3+Cpx3+Amp3+Pl3+Qtz3+Ilm3±Mag3 693–796 0.60–0.84 GPa. A final greenschist to sub-greenschist facies event was recorded exsolution actinolite albite a retrograded well occurrence prehnite, chlorite calcite minerals. Accordingly, clockwise P-T path concluded basis different asseblage. Cathodoluminescence imaging, trace element zircons similar charactistics three episodes Paleo–Meso Proterozoic events. These are events preserved pelitic Jiao-Liao-Ji belt (JLJB) 207Pb/206Pb ages 2.0‒1.9 Ga metamorphism 1.86‒1.84 decomposing process, followed retrograde amphibolite related post-orogenic extension age 1.76‒1.74 Ga, resulting exhumation upper crust level.