Hf–Nd Element and Isotope Perspective on the Nature and Provenance of Mantle and Subduction Components in Western Pacific Arc–Basin Systems

attributed directly to subduction. One option consistent with Hf–Nd This paper develops methods for using the integrated study of systematics is that the positive Hf anomalies in the Protoarc boninites Hf–Nd element and isotope covariations to define the nature and were caused by fusion of mafic veins in their shallow mantle sources. provenance of the mantle and subduction inputs to subduction Comparison with published data on other arcs shows significant systems. In particular, it can be demonstrated that (1) Hf–Nd inter-arc variations. For example, the subduction components in isotope space permits discrimination between mantle of Pacific and near-continent arcs (Banda, Lesser Antilles) appear to have lower Indian provenance, (2) displacements from mantle arrays on Hf–Nd Nd/Hf ratios more consistent with sediment fusion, and at least isotope and trace element projections can be related to the magnitude, one arc (Tonga–Fiji) carries evidence of temporal variations in source and composition of the subduction input, and (3) Hf–Nd mantle provenance. isotope and trace element covariations can be used to interpret high field strength element (HFSE) anomalies [specifically, Hf anomalies on extended rare earth element (REE) patterns] in subductionrelated magmas. These methods are tested using published volcanic arc data coupled with new data from the many components of the Izu–Bonin–Mariana (IBM) subduction system, namely the pre