Variation in the mantle sources of the northern Izu arc with time and space - Constraints from high-precision Pb isotopes

In the northern part of the Izu-Bonin arc, Miocene to Pliocene volcanism was active over a much wider back-arc region than present, and these lavas show the greatest influence of sediment melt generated at slab depths of > 250 km. However, in the Quaternary active volcanism was constrained to the vicinity of the volcanic front. This Quaternary magmatism can be related to the release of fluid from the slab at relatively shallow depths (110-200 km). These spatial and temporal chemical variations could be related to either the change of the angle of subducting Pacific Plate and/or changes in the regional stress regime (e.g. resulting from the collision of the Izu-Bonin arc with the Honshu arc or in association with initiation of rifting in the south).