Extremely low-Ni olivine as a tracer of carbonate-rich sediment recycling beneath the southwestern Okinawa Trough

Carbonate recycling in subduction zones has a strong influence on arc magmatism and carbon reservoirs in the mantle. However, geochemical evidence of carbonate recycling during subduction, especially at sub-arc depths, is rare and the related process is poorly understood. In this study, we document high-Mg olivines (81–91 mol.% forsterite) with extremely low Ni concentrations (mostly