© A. O. Volynets 1,2, T. G. Churikova 1, G. Werner 2

1 Institute of Volcanology and Seismology FED RAS;
2 GWZ, Georg-August Universitat Gottingen, Goldschmidtstrasse 1, Gottingen 37077, Germany;
Mail address: Russia 683006, Petropavlovsk-Kamchatsky, Piip Avenue 9.
E-mail: [email protected]

Major, trace elements content of Late Pleistocene-Holocene volcanic rocks from Sredinny Ridge, Kamchatka, are studied for more then 200 km-long profile from Ichinsky volcano on the south-east to Tekletunup volcano on the north-west. In its southern part profile represents back-arc of the island arc system of Kamchatka. At the latitude of Alnej volcano profile intersects triple junction of Kurile-Kamchatka and Aleutian island arcs, and in the northernmost part it is more then 100 km outside the borders of the contemporary subduction zone. Nonetheless, rocks from all studied volcanic centers have similar geochemical features, belong to calc-alkaline medium-high-K series and are characterized by strong subduction signature (Nb-Ta trough, elevated Cs, Rb, Ba, Th, U, K, Sr, Pb concentrations). Observed variations in major and trace element compositions can be described by three-component mixing model of variably depleted N-MORB source, enriched OIB-like component and slab-derived fluid. Traces of slab melting (adakite component) are found in Alnej-Chashakondzha massif western slope.