Anomalous seismic structure beneath the Klyuchevskoy Group, Kamchatka

Abstract

[1] The Klyuchevskoy Group is among the most active volcanic features on Earth, yet its position within the Kamchatka subduction zone is hard to explain with a simple tectonic mechanism. The geochemistry of Klyuchevskoy Group lavas is typical for volcanic products resulting from flux melting in the mantle wedge, yet the depth to the subducting Pacific plate beneath it is much larger than the average depth of volatile release in subduction zones. We present new seismological constraints on the upper mantle structure beneath the Klyuchevskoy Group and identify a planar dipping seismic feature in the mantle wedge which is ∼100 km deep and appears to be sharply bounded. We hypothesize that this upper mantle structure may be the true source of melts erupting at the Klyuchevskoy Group, and that the presence of this feature may explain both the extraordinary productivity of the Klyuchevskoy Group and its unusual location.