ИСТИНА

Two geochemical transects were carried out through Kamchatka: one SE-NW across the arc and one SW-NE trending along the Sredinny Range (SR) in back arc zone. These data constrain magma source in space and time and allows us to relate these to tectonic position setting of the region at a given time. The cross arc transect based on Quaternary rocks showed continuous geochemical zonation from arc front to back arc of present subduction zone, including strong and gradual increase in LILE, LREE and HFSE in whole rocks. The transect along the SR comprises two age groups of volcanic rocks each with uniform in geochemical features. Late Miocene-Pliocene rocks (3-6 Ma) represent voluminous plateau lavas of depleted basalts with low HFSE and HREE. Fluid-mobile elements are enriched and enrichment patterns are in fact similar to the typical arc front lavas. The younger Quaternary rocks (<1 Ma) are represented by monogenetic cones and stratovolcanoes that combine the typical LILE/HFSE-enrichment of a subduction setting with enrichment in all incompatible elements.