Grenvillian Metamorphism of Sillimanite-Garnet Feldspar Paragneiss in the Larsemann Hills, East Antarctica and Tectonic Implications

The medium- to high-grade metamorphic rocks exposed in the Larsemann Hills of East Antarctica are the main components of the Prydz Bay basement rock series. They are ideal for studying the composition and evolution of the Prydz Belt. In this paper, detailed petrological analyses, phase equilibrium modeling, and zircon analyses were performed on the sillimanite-garnet feldspar paragneiss from the Mirror Peninsula in the Larsemann Hills. The study results show that the paragneiss consists of the mineral assemblage garnet + cordierite + plagioclase + ilmenite + sillimanite + quartz +/- biotite +/- K-feldspar and underwent HT metamorphism in the Grenvillian Period (similar to 980Ma). The peak metamorphic assemblages (M-1) are represented by the matrix minerals garnet + plagioclase + K-feldspar + ilmenite + quartz, the phase equilibrium modeling shows that the metamorphic conditions of the paragneiss are similar to 820 degrees C, similar to 9. 6kbar. The maximum deposition age of the paragneiss is constrained between similar to 1073Ma and 980Ma. It was formed by denudation and deposition of the Mesoproterozoic magmatic rocks, and the source rock belongs to S-type granite. The magmatic zircons in the paragneiss have lower LREE and higher HREE content than those of the metamorphic zircons in the same rock. During the Grenvillian Oeriod, the Larsemann Hills had a near-isothermal depressurization clockwise metamorphic P-T trajectory, experienced the process of continent-continent collision and then rapid exhumation and sedimentation, the S-type granite was associated with this process.