Ancient mantle plume components constrained by tungsten isotope variability in arc lavas

Abstract

Tungsten isotope anomalies in modern rocks are exclusively associated with plume-related basalts and may provide a unique tool to identify recycled plume material in subduction zone magmatism. In Central America, the Cocos and Coiba Ridges are subducting with the Cocos plate. These ridges may introduce material into the arc magma source that was derived from the Galápagos plume, which has been shown to carry anomalous 182W signatures. Here, we report negative μ182W values together with trace element data for <5 Ma old adakites and back-arc basanites, as well as accreted basalt terranes that formed as a result of Galápagos plume activity in the last 70 Myr. In adakites and basanites, these μ182W deficits derive from a slab melt component that dominates the W budget of their source. In addition, negative μ182W in accreted mafic terranes attest to the longevity of the primordial W isotope signature in the Galápagos plume and the involvement of a Galápagos-related magma source in the Central American arc system over time.