Fluid-rock interactions in slow-spread oceanic lithosphere during spreading, subduction and exhumation
Thomas Gyomlai actuellement à l’IPGP nous présentera sa recherche sur les interactions fluide-roche dans la croute océanique.
Abstract
I studied these interactions in two areas: (1) The Vema Lithospheric Section in the Atlantic Ocean, which illustrates how the low and variable amount of magmatism at slow-spreading ridges produces a discontinuous and chemically heterogeneous mafic crust. In particular, the formation of oxide gabbro due to a highly differentiated Fe-Ti-(V)-(P)-saturated melt (nelsonitic) is key in the distribution of deformation and alteration by sea water. (2) The Syros ophiolite in Greece, which illustrates how this already hydrated lithosphere is the setting for major fluid ingressions and reactions along the subduction interface and associated with element (e.g., Ca, Mg, REE, Li) mobility. In both areas, petrogeochemical and hygrochronometric analyses are used to study the significance and scale at which fluid flows occur in slow-spread oceanic lithosphere and their impact on triggering of seismicity, element recycling, mechanical coupling at the plate interface and arc magmatism.