Molybdenum isotope systematics in subduction zones

This study presents Mo isotope data for arc lavas from different subduction zones that range between delta Mo-98/95 = 0.72 and +0.07%o. Heaviest isotope values are observed for the most slab fluid dominated samples. Isotopically lighter signatures are related to increasing relevance of terrigenous sediment subduction and sediment melt components. Our observation complements previous conclusions that an isotopically heavy Mo fluid flux likely mirrors selective incorporation of isotopically light Mo in secondary minerals within the subducting slab. Analogue to this interpretation, low delta Mo-98/95 flux that coincides with terrigenous sediment subduction and sediment melting cannot be simply related to a recycled input signature. Instead, breakdown of the controlling secondary minerals during sediment melting may release the light component and lead to decreasing delta Mo-98/95 influx into subarc mantle sources. The natural range between slab dehydration and hydrous sediment melting may thus cause a large spread of delta Mo-98/95 in global subduction zone magmas. (C) 2016 Elsevier B.V. All rights reserved.