P-T-t-d evolution of Brattnevet Peninsula, Larsemann Hills, East Antarctica

Brattnevet Peninsula, Larsemann Hills, comprises metamorphosed acidic rocks, sedimentary rocks and basic igneous suite belonging to timespan of 920-478 Ma and have experienced three phases of deformation and metamorphism. The first and second phase of deformation gave rise to moderately plunging isoclinal and open to closed folds, respectively and the third phase resulted into broad warping. M-1 prograde (amphibolite) and M-2 peak (granulite) and M-3 retrograde (decompression) events have been inferred. In pyroxene granulite, inclusion assemblage of quartz, biotite, plagioclase and ilmenite in hornblende correspond to the relict M-1 amphibolite grade event associated with D-1-D-2 deformation events (occurred at similar to 920 Ma; 538-692 degrees C at similar to 6kb). However, the presence of enstatite, diopside, quartz, biotite, ilmenite and plagioclase in pyroxene granulite and sillimanite, biotite and almandine garnet and plagioclase in metapelite indicates granulite facies during M-2 event (similar to 530 Ma; 868-920 degrees C at similar to 6.7 kb). The retrograde M-3 event (500-480 Ma; similar to 620 degrees C at similar to 5kb) is largely depicted in pyroxene granulite and metapelite by coronal and symplectite cooling textures. The study shows a clockwise P-T path and suggests the crustal evolution of Larsemann Hills area have commenced at the wanning stages of Grenvillian Orogeny and imprinted by the Pan-African orogenic event in the terrane.

Automated summary

The Brattnevet Peninsula in Larsemann Hills consists of metamorphosed acidic rocks, sedimentary rocks, and basic igneous suite dating back to 920-478 Ma, with three phases of deformation and metamorphism. The study reveals a clockwise P-T path and suggests that crustal evolution in the Larsemann Hills area started during the Grenvillian Orogeny and was influenced by the Pan-African orogenic event.