DISTRIBUTION OF VOLCANOES OF THE KURILE ISLAND ARC AND THE PROBLEM OF MAGMA GENERATION

Abstract

The recent study of submarine volcanoes of the Kurile island arc on cruises of the R/V Vulkanolog revealed the distribution in space of all Holocene volcanoes here and, therefore, allowed them to be analyzed in connection with one of the main problems of volcanology, the generation of island-arc magmas. We show the arrangement of 81 submarine and 105 subaerial volcanoes. Nothing is yet known about the activity of these submarine volcanoes, but 42 of the subaerial are still active. Nearly all volcanoes are clustered into chains oriented across the general trend of the arc at different angles to it. Some chains intersect, as though forming a kind of 'cross system'. Others are oriented in a subparallel or almost perpendicular direction to the arc. Systematic compositional differences between the volcanic rocks in frontal and back-arc parts of island arcs suggest that two, and in some areas possibly three, zones of a relative increase in magma generation are a general feature of island arcs. This should be considered in modeling the petrogenesis of island-arc series of volcanic rocks.