Monitoring dehydration reactions in natural serpentinite assemblage at subduction zone conditions with implications for fluid transfer, arc

The main objective of this follow-up proposal to complete the characterization of the successive dehydration reactions in rocks containing multiple hydrous phases during subduction using in situ X-ray diffraction. We focus on the “brucite + serpentine” system at HP (up to 5 GPa) and HT (up to 750°C). During subduction, this assemblage reacts and produces aqueous fluids together with olivine. While the dehydration reaction of antigorite has been intensively studied, the reactions in systems that contain several hydrous phases have been poorly investigated experimentally as they were not considered as relevant for fluid production in subduction zones. But recent field investigations and thermodynamical modelling show that reactions with multiple hydrous phases can produce major fluid releases of in subduction zones. Our aim to fully understand how the presence and composition of multiple phases influence the nature, the P/T dependence and the kinetics of these dehydration reactions.