N.V. Tsukanov1, S.G. Skolotnev2

Study on morphology, internal structure, geochemistry and local U-Pb dating of zircons from two samples of gabbro from Olenegorsky massif of ophiolitic association of Kamchatsky Peninsula (Kamchatka) showed presence of xenogenic zircon grains in the gabbro. Zircons of Proterozoic and Archaean age prevail: 1498±22, 1518±26, 1900, 2306±7, 2631±25, 2721±35 Ma; among them there are grains of both magmatic and metamorphic origin. Grains of Cenozoic age 64.8±3.2 Ma with metamorphic nature were found in small amounts; apparently they were initially formed during origination of metamorphic rocks and nappe-folded basement of the island arc. Data on Cenozoic age of zircons from Olenegorsky Massif’s gabbro (64.8±3.2 Ma) confirm our previous conclusion that Olenegorsky gabbro was formed later than supra-subduction ophiolite complex had been formed; these data also give opportunity to combine them in a single ophiolite complex with basalts of Paleocene-Eocene Kamensky formation.

Keywords: supra-subduction ophiolites, gabbro, zircons, age, Kamchatka, ionic microprobe.