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.

► We present results of a multidisciplinary study of Central Kamchatka volcanic arc.
► We report a low velocity structure at ~ 100 km depth within the mantle wedge.
► We report variability of lava chemistry driven by melt input from two source regions.
► Petrological modeling indicates a source much shallower than the depth of subduction.
► We argue for a second contributing melt source within the mantle wedge.