Abstract
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.
Highlights
Arc-related magmas are frequently enriched in Au, Pt and Pd in respect to MORB and OIB igneous suites
Platinum and palladium enrichments are common in igneous rocks and magmatic/hydrothermal mineralization in subduction zones
High gold contents in some arc-related ultramafics such as the IldeusLucha complex (ILC; Table 1) in the Mesozoic Stanovoy arc can be linked to metasomatic enrichment of sub-arc mantle sources by auriferous slab-derived (H2O+Cl) fluids
Summary
Mantle-wedge xenoliths (peridotites and pyroxenites) in Kamchatka display evidence for multi-stage metasomatism by slab-derived melts and fluids reflected in their modal mineralogy, trace elements and isotope characteristics [4,7,8]. Ural-Alaska intrusions are believed to form via crystal fractionation of primitive melts (picrites or arc ankaramites) derived from sub-arc mantle wedge sources [4,9,10] Their Pt signatures (and associated PGE mineralization) can be reflecting Pt-enrichments in the mantle wedge due to sub-arc metasomatism [4,7,8] and/or to the fractionation of Pt-alloys during crustal differentiation of arc-related primary magmas [9,10]. High gold contents in some arc-related ultramafics such as the IldeusLucha complex (ILC; Table 1) in the Mesozoic Stanovoy arc can be linked to metasomatic enrichment of sub-arc mantle sources by auriferous slab-derived (H2O+Cl) fluids
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