TRANSITION FROM THE CONTINENTAL MARGIN OF KAMCHATKA TO THE ISLAND ARC OF THE KURILE ISLANDS: FEATURES OF VOLCANISM, CRUSTAL DEFORMATION AND GEOPHYSICAL PARAMETERS OF THE SLAB
O.V. Bergal-Kuvikas1, M.M. Buslov2, N.A. Bushenkova3, A.A. Dolgaya1
1Institute of Volcanology and Seismology, Far Eastern Branch of the Russian Academy of Sciences, Petropavlovsk-Kamchatsky, Russia
2V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
3Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
Keywords: Continental margin, island arc, slab, volcanism, Kamchatka, Shumshu island, Kurile islands
Abstract
Magmatism manifestations in the transition zone from the continental margin of Kamchatka to the Kurile island arc and some geophysical parameters of the subducted oceanic plate of the Northwestern Pacific are considered. The presence of the Miocene coastal volcanic (Pribrezhny) complex at the base of the South Kamchatka volcanic belt contributes to intense crustal processes causing caldera-forming eruptions in the Holocene. The Northern Kuriles are characterized by initiation of areal volcanism associated with crustal fault zones. Anomalous is the absence of volcanism on Shumshu island proximal to Kamchatka. Seismic tomography data reveal a high seismic velocity anomaly below it, which can explain this phenomenon. Based on the presented data an assumption is made about existence of a seafloor elevation on the slab, whose submergence led to disintegration of the melting regions responsible for generation of volcanism.
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