Gold mobility in subduction zones, the slab perspective

Arc environments are locally gold-endowed and it has been long hypothesized that gold mobilization during slab dehydration could affect mantle composition and arc Au-fertility. Here, we determine gold mobility during prograde high pressure-low temperature metamorphism of both metavolcanic and metasedimentary rocks from the islands of Santorini, Ios, Naxos and Syros (Greece). These rocks experienced peak greenschist to upper-blueschist/eclogite facies metamorphism, allowing determination of large-scale gold mobility within a subduction zone. Our data shows that gold is significantly mobilized by fluids at the blueschist-eclogite facies transition. In the associated mélange zones at the slab-mantle interface gold shows heterogeneous concentration but is not enriched, implying only partial retention of gold in the mélange and its mobilization across the slab-mantle interface. Furthermore, the intrinsically complex lithologies and heterogenous gold concentrations of these mélange zones contribute to the slab component inherent to arc magmatism, and can affect magmatism gold-fertility.