N. I. Seliverstov

Institute of Volcanology, Far East Division, Russian Academy of Sciences,
Petropavlovsk-Kamchatskii, 683006, Russia

This paper presents the modern views on the hydration of the Pacific plate sector bordering Kamchatka with due allowance for its regional structure. Deep lithospheric temperatures were estimated taking into account the ages of the lithospheric blocks and the specific structure of the sedimentary cover. It was found that the northern sector of the Pacific plate, located opposite the Klyuchevskoi volcanic group, was distinguished by its abnormally high bound water content. Potential geodynamic consequences of this phenomenon are discussed. It is shown, in particular, that the abnormal geodynamic characteristics in the northern segment of the Kuril-Kamchatka arc, such as the westward shift of the volcanic belt, the flattening and insignificant length of the Benioff zone, the huge volcanic edifices, and the absence of large calderas, may owe their origin to the abnormally high hydration of the northern sector of the Pacific plate. The original positions of the Hydroconvectional Hypothesis of Island Arc Magmatism are given.