The Karymskii Volcanic Center: Volcanic rock geochemistry

Abstract

This paper is concerned with the petrology and geochemistry of rocks found in the Karymskii Volcanic Center (KVC), which is the largest volcanic center in the Eastern volcanic belt of Kamchatka. The KVC has been built in a rhythmic manner since the Late Pliocene, forming successive differentiated rock complexes. The pattern of variation for major and minor elements in the KVC volcanic rocks can be explained by the fractionation of mineral phases from the parent melt. The process involved enrichment of the residual melts with alkalis and lithophile elements (Rb, Ba, Sr, Pb, Th, U, REE), as well as depletion in coherent elements (Ni, Cr, Sc, Ti). A geochemical study of the KVC volcanic rocks shows that these are typical island arc formations. The relationships between incompatible elements suggest a two-component magma generation system: a depleted mantle source (N-MORB) and suprasubduction fluids (an island arc component). The melt may have been contaminated by a metasomatically altered substratum in the top of the intermediate chamber with added crystalline cumulus phases (and melts) of the earlier magma generation phases in the KVC.