XPot de Nestor Cerpa

Nestor Cerpa (Université d’Oxford) présentera ses travaux dans le cadre d’un X-Pot le lundi 20 Novembre à 14h.

Titre : Physical controls on pathways of slab-derived fluids through the mantle wedge: Implications for hydrous melting

Abstract: Arc magmas are thought to be generated largely by hydrous melting induced by the addition of water from the subducting slab into the hottest region of the overlying mantle wedge. While the release of aqueous fluids from the slab is predicted to occur over a wide region, arc volcanoes tend to form in a narrow region situated at ~100 ± 30 km above the top of the slab, suggesting non-trivial pathways of aqueous fluids and magmas through the mantle wedge. In particular, it has been suggested that some mechanism focus fluids beneath the arcs regardless of the thermal-state of the subduction zone.
My recent work has consisted in exploring the physical factors that may control the migration of slab-derived fluids in the mantle wedge, using 2-D numerical models of coupled Darcy’s-Stokes flow. The numerical results suggest that spatial variations in mineral grain size and shear viscosity in the mantle wedge may play a key role in focusing fluids towards the sub-arc region over a range of subduction parameters [Cerpa et al., 2017]. Further, the flux of fluid release from the slab as well as fluid properties (viscosity/density) are also likely to influence fluid flow. The range of possible values spanned by those factors lead to the prediction of a range of possible fluid pathways through the flowing mantle, producing various scenarios for hydrous melting in the hottest part of the mantle wedge.