Metamorphic timescales of Neoproterozoic high-pressure granulites constrained by multi-mineral petrochronology: a case study from the Southern Brasília Orogen (SE Brazil)

Timescales of Neoproterozoic high-pressure granulites from the Carvalhos Klippe (Southern Brasília Orogen) were constrained through multi-mineral petrochronology. The high-grade metamorphism is related to continental collision processes during the assembly of West Gondwana and provides valuable insights on duration and rates of collisional settings in the Neoproterozoic. Most of the investigated samples comprises coarse-grained rutile-kyanite-garnet-orthoclase granulites, reaching peak metamorphic conditions of ~ 825°C and 12 kbar, based on phase equilibrium modelling and Zr-in-rutile thermometry. Prograde to a near peak stage (630 − 620 Ma) was constrained by garnet Lu-Hf and U-Pb ages from high Y-HREE and low Th/U monazite domains. Low Y-HREE, high Th/U and Eu/Eu* monazite domains record the metamorphic peak (615 − 605 Ma) after substantial garnet growth, presence of melt and plagioclase consumption. The retrograde stage highlighted by high Y-HREE and Th/U and depleted Eu/Eu* monazite domains, reflects garnet dissolution and melt crystallization during the retrograde path (605 − 600 Ma). Zircon ages have a main cluster between 630 and 605 Ma, most likely related to near-peak cooling. Cooling ages obtained by rutile and apatite U-Pb and biotite Rb-Sr ranging from 570 to 540 Ma suggest slow cooling rates of 2–8°C/Myr during the retrograde path, contrasting with the modern collisional orogens due to hotter mantle temperatures or low erosion rate and/or heat-producing elements concentration. This study demonstrates that the timescales of high-pressure granulites may provide a robust framework for understanding continental settings throughout the Earth’s history.