Gold, platinum and palladium enrichments in arcs: role of mantle wedge, arc crust and halogen-rich slab fluids

Arc-related magmas are frequently enriched in Au, Pt and Pd in respect to MORB and OIB igneous suites. Magmatic arcs commonly host large-scale hydrothermal Au and Au-Cu and PGE mineralization related to young volcanic systems and zoned ultramafic complexes respectively. Island-arc mantle xenoliths show Au, Pt, Pd enrichments related to mantle wedge metasomatism by slab-derived fluids. Long-lived plumbing systems in arc crust (arc magma chambers) show further enhancement of Au, Pt and Pd enrichments through subduction-related metamorphic and metasomatic processes in the presence of halogen-rich, aqueous fluids. We propose that Au-Pt-Pd enrichments in arcs are caused by mantle wedge-slab interactions followed by differentiation and metamorphism of magmatic conduits in arc crust.