POST-ERUPTION CARBONATE DEPOSITION ON KAMCHATKAN VOLCANOES

Abstract

The aim of this paper is to discuss the deposition of carbonate minerals during the post-eruption process on the fumarolic fields of the Great Tolbachik Fissure Eruption and on the cinder cones of the Tolbachik area, the lavas of which show wide chemical variations and form a series of magnesian basalts of medium alkalinity to subalkaline aluminiferous basalts. It is shown that the deposition of carbonate minerals was related mainly to supergene processes developed in fumarolic fields. Their protominerals were Ca and Mg chlorides produced by gas-rock reactions. The occurrence of carbonates in the post-eruption incrustation on the Tolbachik cinder cones is attributed to the high carbon content of the volcanic rocks, produced by the rapid intrusion of basalt dikes from depths of 20-40 km, and to the high explosivity of the magnesian basalt eruptions.