Mechanism of magma ascent and deep feeding channels of island arc volcanoes

Abstract

The paper discusses the mechanism of deep magma activity beneath island are volcanoes and similar structures on the basis of data from geophysical investigations in Kamchatka; the analyses of forces that cause the ascent of magma; and related phenomena that are due to hydrostatic forces.It is shown that the ascent of magma through the astnenosphere occurs most likely in magma columns with a diameter of approximately 700–2,000 m and with a velocity of about 0.8–3 m/year. A regular line of such columns spaced in Kamchatka at a distance of about 30 km gives rise to a chain of separate Etrge volcanoes or volcanic centers. Ultrabasic magmas are most likely accumulated near the M discontinuity, whereas the apparent place of andesitic magma accumulation is in the earth’s crust near the boundary between the basement and sediments.