Metamorphic evaluation and tectonic implications of Mozhugongka garnet amphibolites, Lhasa terrane, Tibet

The Mozhugongka garnet amphibolites exhibit mineral assemblage of garnet, amphibole, albite, quartz, phengite, epidote, rutile, and chlorite. Based on the metamorphic textures, two metamorphic stages (peak metamorphism: M2; retrograde metamorphism: M3) can be observed: M2: Grt + Hbl + Pl + Qz, M3: Hbl + Pl + Qz. Metamorphic P-T calculations were conducted by GHPQ and HPQ geothermobarometers for two garnet amphibolite samples. The results for M2 and M3 are ~15-16 kbar/550-580 °C and ~6-9 kbar/400-490 °C, respectively. Mozhugongka garnet amphibolites can be geochemically and geochronologically compared with the Bailang eclogites, as both Bailang eclogites and Mozhugongka amphibolites possess OIB affinity and share similar exhumation path. Based on geochemical and retrograde metamorphic similarities, Mozhugongka garnet amphibolites may have originated from eclogites, which also exhumed during Triassic (219±1.2 Ma) along with Pangna blueschist, Jilang, Songduo and Bailang eclogites. Mozhugongka garnet amphibolites possibly mark the westward extension of Songduo metamorphic complex along with Pangna blueschist