Evidence for two upper mantle sources driving volcanism in Central Kamchatka

Volcanoes of the Central Kamchatka Depression (CKD) form the most active arc volcano system in the world. Volcanoes of the CKD are positioned ~. 170. km above the subducting Pacific Plate, in excess of the typical global value of ~. 100. km for arc volcanism. We present results of a combined geophysical and petrological study of the main volcanic center in the CKD, and argue for the presence of a second contributing melt source within the mantle wedge. This region of melt generation is separate from the fluid fluxed region above the subducting Pacific Plate; it may explain the presence of the active CKD arc in its current location.Results of receiver function imaging of the upper mantle beneath CKD reveal a distinct area of low velocities at approximately 110. km depth that is clearly distinct from the crust of the subducting Pacific Plate. Results of petrological modeling suggest presence of pyroxenite source melt contribution to CKD lavas, alongside previously described peridotite source melts. We contend that our results advance the notion that melting at two separate sources, rather than the simple flux-induced melting within the mantle wedge, drives volcanoes of the CKD.