Himalayan zircons resurface in Sumatran arc volcanoes through sediment recycling

Understanding 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 similar to 30 to 45% of the magma source of the arc volcanic rocks near Toba.

Automated summary

Understanding the processes of subducted sediment recycling in subduction zones is crucial for deciphering the interactions between Earth's crust and mantle. This study examines Quaternary arc basalts and andesites from Sumatra Island, Indonesia, using along-arc geochemical variations and zircon U-Pb-Hf-O isotopes to assess the mode of sediment recycling in subduction zones. The findings indicate that some of the volcanic rocks near Toba Caldera derive their composition from subducted terrigenous sediments, which mix with the mantle. Furthermore, thermodynamic modeling suggests that the subducted sediments do not melt on the slab surface, but instead form diapirs that rise buoyantly through the hot mantle wedge and contribute to a significant portion of the magma source.