Metamorphic evolution of the juvenile Serrinha forearc basin in the southern Brasiliano Orogen

Understanding the accretion of an oceanic island arc to a craton is a major issue in unravelling the evolution of the continents. P-T-t conditions registered in metamorphic rocks, the boron isotopic compositions of tourmaline provide essential information to delimit the accretionary processes. The Tonian-Cryogenian Sao Gabriel Terrane is a prominent juvenile structure in the southern Brasiliano Orogen that records key information about accretionary processes. Limited previous studies have investigated the Sao Gabriel Terrane, with little presently known about the metamorphic conditions. To pursue the objective, we combined multiple methods, including pseudosection modeling, U-Pb garnet geochronology and δ11B isotopes of tourmaline applied to one key sample from the Serrinha Formation of the Sao Gabriel Terrane. The recorded peak P-T conditions occurred at 4.5–5.1 kbar and 536–555 °C. U-Pb dating of low-U (