Heavy Mo isotope composition of northern Bataan adakites, Philippines: Evidence for fore-arc subduction erosion?

Abstract The identification of an eroded fore-arc crust component in arc magmas is challenging due to the combined effects mantle metasomatism and crustal assimilation–fractional crystallization. In this study, molybdenum (Mo) isotope compositions are used conjunction with Sr-Nd-Hf isotopic elemental data identify components adakites from Cuyapo Balungao volcanoes northern Bataan segment Luzon (Philippines). Mo ratios (?98/95Mo, relative NIST SRM 3134 standard) these increase increasing ?Nd (+4.3 +5.6) Ba/Nb (206–286). low ?98/95Mo (?0.36‰ ?0.26‰) coupled suggests contributions residual slab, which lost isotopically heavy during dehydration. Interestingly, high (?0.18‰ 0.00‰) have Mo-Sr-Nd-Hf similar those basement. Fractionated Nb/Ta (16–18) Sr/Y indicate coexistence melt rutile garnet ± amphibole assemblages, corresponding a source region (>~45 km) below present (~33 km). This thus origin partial melting wedge rather than upper-plate crust. Our work not only demonstrates that isotopes may be potential tracer but also highlights lavas ?98/95Mo, ?Nd, emplaced at subduction zones juvenile result erosion.