Abstract

The presence of a tear in the subducting African slab has a strong effect on Neogene magmatism in western Turkey, but its influence on volcanism in the Quaternary Aegean arc to the west is unknown. In order to investigate to what extent arc volcanism can be affected by slab-parallel mantle flow from a slab window, we present new trace element and Nd-Pb isotope data for Nisyros and Santorini volcanoes. Trace element modeling allows quantification of the infiltration of trace element–enriched mantle of subslab provenance through the slab tear into the depleted Aegean mantle wedge. Primitive Nisyros magmas record melting of a mixed source that contains as much as 10% of the enriched, subslab mantle component, and a contribution of this component can be traced as far west as Santorini, ∼250 km away from the slab tear. We conclude that trace element and Nd-Pb isotope variations between Nisyros and Santorini do not require along-arc variations in subducting sediment composition, but reflect the heterogeneous nature of the Aegean mantle wedge related to infiltration of subslab mantle through the slab tear. Our geochemical evidence is in excellent agreement with predictions made on the basis of mantle tomography and anisotropy that indicate toroidal mantle flow around the edge of the Aegean slab. This implies that suction related to slab rollback can lead to the infiltration of subslab mantle material and slab-parallel mantle flow, thus potentially strongly influencing arc volcanism, processes that perhaps need greater assessment in other arc systems.

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