Hybridization-melting and harzburgite melting: Links with continental crust formation, redox conditions, and volatile and critical metal transfers

Zoom link: https://u-paris.zoom.us/j/84526770346?pwd=dTdvSEFLbWp3Vzc2ZTN4TFIwd0c4UT09 The nature of mantle wedge melting processes remains highly debated because subduction zone magmas are modified en route to their final emplacement sites. In particular, recent models from the literature tend to undermine any specific control of mantle wedge melting processes on the critical metal endowments of magmas. Detailed studies of fresh sub-arc mantle peridotites from the Western Pacific have shed new light into mantle wedge magmatic processes. In this talk, I will present petrogenetic backgrounds for the two main partial melting processes identified in studies of those mantle-derived samples; hybridization-melting and harzburgite melting. By combining geochemical and spectroscopic data with petrological (thermodynamic) modelling for the two contexts, I will further relate redox conditions with the speciation and abundances of volatile species, and the transfer of critical metals (e.g. Ni, Cu, Zn, Ag, Sn, W, Re, Au and platinum-group elements). Emphasis will be given on coupling different methods to reach a comprehensive understanding of a given petrological process. These methods notably include experimental and analytical treatments of mantle-derived melt inclusions, laboratory syntheses of silicate liquid analogues (glasses), and developments of new thermodynamic models for the behavior of chalcophile and highly siderophile metals in magmatic systems. Finally, I will list some prospects in mineral physics and geochemistry to better address petrological processes involved in critical metal transfer and deposition.