Moho carbonation at an ocean-continent transition

Rémi Coltat (1) , Philippe Boulvais (1) , Yannick Branquet (1, 2, 3) , Antonin Richard (4) , Alexandre Tarantola (4) , Gianreto Manatschal (5)

1 GR - Géosciences Rennes
2 ISTO - Institut des Sciences de la Terre d'Orléans - UMR7327
3 Géodynamique - UMR7327
4 GeoRessources
5 ITES - Institut Terre Environnement Strasbourg

Carbonation of mantle rocks during mantle exhumation is reported in present-day oceanic settings, both at mid-ocean ridges and ocean-continent transitions (OCTs). However, the hydrothermal conditions of carbonation (i.e., fluid sources, thermal regimes) during mantle exhumation remain poorly constrained. We focus on an exceptionally well-preserved fossil OCT where mantle rocks have been exhumed and carbonated along a detachment fault from underneath the continent to the seafloor along a tectonic Moho. Stable isotope (oxygen and carbon) analyses on calcite indicate that carbonation resulted from the mixing between serpentinization-derived fluids at ~175 °C and seawater. Strontium isotope compositions suggest interactions between seawater and the continental crust prior to carbonation. This shows that carbonation along the tectonic Moho occurs below the continental crust and prior to mantle exhumation at the seafloor during continental breakup.

Domains: Sciences of the Universe [physics]; Earth Sciences

Rémi Coltat, Philippe Boulvais, Yannick Branquet, Antonin Richard, Alexandre Tarantola, et al.. Moho carbonation at an ocean-continent transition. Geology, 2022, 50 (3), pp.278-283. ⟨10.1130/G49363.1⟩. ⟨insu-03469219⟩