Pan-African metamorphism and magmatism in the Prydz Belt,East Antarctica:a geochronological perspectiveOA

The Prydz Belt in East Antarctica underwent extensive reworking during the late Neoprotertozoic-early Paleozoic Pan-African orogeny,which is characterized by granulite facies,clockwise P-T paths,and high dT/dP values.This study compiles the existing age and composition data of zircon and monazite from metamorphic rocks and links their key characteristics to the metamorphic evolution of the Prydz Belt.The frequency of zircon U-Pb ages starts to increase noticeably from～555 Ma,peaking between 530 Ma and 520 Ma,followed by a dramatic decline after 520 Ma.High Th/U values(>0.1)of zircon are observed from～545 Ma,displaying a noticeable increasing trend in Th/U values before a rapid decline from～520 Ma.The frequency of monazite ages progressively increases from～540 Ma,reaching its peak at 515 Ma,and then rapidly decreases after 490 Ma.Combined with the crystallization behaviors of zircon and monazite,this study suggests that the systematic changes in Th/U values of zircon after 545 Ma indicate a transition in the thermal regime of the Prydz Belt towards the cooling stage.Abundant growth of zircon and monazite corresponds to the post-peak cooling process,while the crystallization peak of monazite lags behind that of zircon by～5-15 Ma,which indicates a relatively low cooling rate.Though the granitic intrusions accompanied the entire metamorphic evolution,the majority of them are younger than 520 Ma.The results suggest that the Pan-African event likely peaked at～555-545 Ma and gradually cooled to near-solidus conditions at～520-510 Ma,with a relatively slow average cooling process.