Slab and Mantle Controls on the Sr–Nd–Pb–Hf Isotope Evolution of the Post 42 Ma Izu–Bonin Volcanic Arc

Abstract

The arc outflux is a hybrid of material fluxes from slab, mantle and crustal sources, whose proportions and composition may vary through time. Here we investigate the causes of temporal variability in the post 42Ma eruptive products of the Izu^Bonin arc in the NW Pacific Ocean basin using Sr^Nd^Pb^Hf isotopes in combination with major and trace element systematics in mafic to evolved arc magmas. Following arc initiation at 50Ma, Izu^Bonin arc for-mation was continuous except for a short period of quiescence (20^23Ma) during back-arc basin formation in the early Miocene.The Sr^Nd^Pb^Hf isotope trends do not co-vary through time. An increasing trend of Pb isotope ratios with time reflects a change in the trench sediment input as it becomes richer in radiogenic Pb. Sr isotopes show no unidirectional trend with time owing to the dominant contribution of unradiogenic Sr from the subducting igne-ous crust (66 % of arc Sr) and mantle (31%) that buffer the