Molybdenum and titanium isotopic signatures of arc-derived cumulates

Fluid migration and/or differentiation of magmas in arc settings are important drivers stable-isotope fractionation elements like molybdenum and titanium, respectively. For both isotope systems, evolved heavier than average arc-basalts, which requires an isotopically light reservoir counterbalancing the heavy felsic lithologies. In attempt to better define this reservoir, we investigate Mo Ti isotopic signatures upper crustal magmatic cumulates comprising hornblendites gabbros from Alpine orogen, Sierra Nevada batholith, Sanandaj-Sirjan zone Kos volcano-plutonic system. The mafic enclaves exhibit compositions ranging that arc-basalts/andesites significantly lighter values (δ49Ti between −0.15 + 0.08‰), is agreement with a Rayleigh distillation model. δ49Ti correlates negatively abundance FeTi oxides, suggesting samples have similar those most hosted pyroxene amphibole. This indicates degree isotopes fractionated melt controlled by fraction incorporated into silicate phases versus oxides. contrast, corresponding more dispersed (δ98MoNIST = −0.02 ± 0.22‰, 2 s.d.) arc-basalts. However, concentrations throughout several cumulate enclave bulk rocks measured too enriched be explained pure fractional crystallization as they do not match modelled melt-cumulate trends. We distinguish purely predominantly fluid mediated processes leading enrichment cumulates, show can play role generation high cumulates.