Granulites of the South Muya block (Baikal-Muya Foldbelt): Age of metamorphism and nature of protolith

High-pressure mafic granulites and garnet pyroxenites occur within the South Muya block as boudins or lenses among metamorphic rocks of the Kindikan Group. Their primary minerals crystallized at 670-750 °C and 9.5-12.0 kbar. Granulite metamorphism peaked at 630 Ma, according to LA-ICP-MS U-Pb zircon ages. Judging by their major- and trace-element compositions and Hf isotope ratios in zircons, the South Muya granulites were derived from differentiated within-plate basalts, which, in turn, resulted from melting of juvenile mantle source and Meso- or Paleoproterozoic crust. The events of granulite and eclogite metamorphism in the South and North Muya blocks, respectively, were coeval and the two blocks were spatially close to each other at the onset of Late Baikalian subduction and collision events.