Asthenospheric upwelling, oceanic slab retreat, and exhumation of UHP mantle rocks: Insights from Greater Antilles

International audienceExhumation of garnet-bearing peridotites has been associated with low density continental rocks. This association does not explain the occurrence of garnet-bearing peridotites in the oceanic subduction zone of the Greater Antilles in Hispaniola. We use numerical models of intra-oceanic subduction to explain exhumation of garnet peridotites without involvement of buoyant continental crust. We demonstrate that rheological weakening of the mantle wedge takes place due to its strong hydration during subduction of serpentinized slow spreading ridge. This weakening triggers upwelling of the hydrated peridotites and partially molten peridotites followed by upwelling of hot asthenosphere and subsequent retreat of the subducting slab. According to numerical modelling of P-T paths this process can explain exhumation of UHP (4GPa) rocks in an intra-oceanic setting