Himalayan zircons resurface in Sumatran arc volcanoes through sediment recycling

Abstract

AbstractUnderstanding the processes of subducted sediment recycling in subduction zones is vital to decipher Earth’s crust-mantle interactions. This study uses along-arc geochemical variations and zircon U-Pb-Hf-O isotopes of Quaternary arc basalts and andesites on Sumatra Island, Indonesia to assess the mode of sediment recycling in subduction zones. The Hf-O isotopes of inherited zircons of the basalts and andesites near the Toba Caldera indicate that some of them were derived from subducted terrigenous sediments mainly sourced from the (eastern) Himalaya. Hybridization of the subducted sediments with the mantle also accounts for the enriched Sr-Nd isotopic compositions of arc volcanic rocks near the Toba Caldera. Thermodynamic modeling indicates that the subducted sediments did not melt on the slab surface. Rather, geochemical evidence supports their formation as diapirs that rise buoyantly through the hot mantle wedge and contribute to ~30 to 45% of the magma source of the arc volcanic rocks near Toba.