GEOCHEMISTRY OF NEOGENE VOLCANIC ROCKS IN THE NORTHERN PART OF THE CENTRAL KAMCHATKA VOLCANIC BELT

New geological and geochemical data on the age and composition of Neogene rocks in the northern part of the Central Kamchatka volcanic belt are presented. K-Ar dating of volcanic rocks determined the age of all studied volcanic rocks to be Late Miocene. The geochemical characteristics of the rocks show that the northern part of the Central Kamchatka volcanic belt is characterized by a complex geological history, in which magma generation processes are governed by the type of mantle matter. The “earliest” among the Late Miocene rocks that make up the Umuvayam and Tolyatovayam complexes (6.7–9.0 Ma) are represented by typical island-arc rocks. Whereas, “later” (5.4–7.7 Ma) volcanic rocks of the Alney and Veemgetver complexes are characterized by an association of rocks with a high proportion of enrichment from the OIB-type source. The magma source corresponded in composition to spinel lherzolite. The enrichment of volcanic rocks in large-ion lithophile elements is explained by the role of fluids introduced into the melts during the melting of the supra-subduction mantle wedge, which probably also underwent modification as a result of supra-subduction metasomatism in the geological past.