Ignimbrite flare-up in Late Cretaceous–Paleocene Japan empowered by hot mantle inflow

Abstract The contribution of subduction parameters, mantle flow, and magmatic systems to the triggering of ignimbrite flare-ups is poorly understood. A re-examination of spatiotemporal variations in igneous activity and Sr–Nd isotopic compositions through Cretaceous to Paleogene, based on a new dataset covering the Japan arc and the Korean Peninsula, shows the existence of two isotopically distinct mantle sources with SrI and εNd(t) higher and lower than 0.7065 and − 3.5, respectively. The more enriched mantle source was introduced into the mantle wedge at 100–60 Ma. The isotopic enrichment in magma in Japan arc peaked at 90–60 Ma, coinciding with the ignimbrite flare-up. This isotopic fluctuation can be explained by the passive upwelling of the asthenospheric mantle induced by the rollback of the flat-slab of the Panthalassa plate subducted beneath the North China Craton began with 150–140 Ma. Our dataset clearly shows that the increase in thermal input from the mantle to the lower crust of the Japan arc was the prime factor in the formation of world-class ignimbrite bodies.