Dating fluid infiltration and deformation in the subducted ultramafic oceanic lithosphere by perovskite geochronology

Carbonated ultramafic rocks (i.e., ophicarbonates) form by peridotite serpentinization and carbonation at the seafloor. Their metamorphic evolution is linked to that of serpentinites, hence dating deformation metamorphism in ophicarbonates will add constraints P-T-t history subducted lithosphere. A potential, yet underexplored, suitable mineral for geochronology perovskite (CaTiO3). We present trace element geochronological data (LA-ICPMS ID-TIMS) from ophicarbonate calcite veins two terranes, Lanzo Massif Val Malenco (Alps). Metamorphic characterized enrichment heavy REE, strong negative anomalies Zr Hf, as well Sr Pb, which are attributed coexistence a Zr-rich phase mobilization these elements fluids, respectively. Other broadly reflect composition protolith allow distinction mafic rocks. In Massif, 49.6 ± 1.0 Ma age shear bands constrains H2-mediated carbonate reduction abiotic methane graphite formation near peak conditions during deformation. Perovskite found cutting across serpentinite foliation its 48.9 0.5 coincides with major thrusting extension event distinct initial nappe stacking. The can be reproduced LA-ICPMS ID-TIMS proposed secondary reference material metamorphic, low U perovskite. These results show yields geologically meaningful UPb ages viable tool date fluid flow oceanic