NEW DATA ON THE AGE AND COMPOSITION OF OPHIOLITES FROM THE KABAK-TAIGA MASSIF (GORNY ALTAI)

The combination of newly obtained geological, petrological and geochronological data on the rocks from the Kabak-Taiga ophiolite massif of the Gorny Altai and already published materials on similar characteristics of the ophiolites from Tuva allows us to conclude that an initial back-arc basin at the rear of the Tannuol island arc dates back to the Vendian – Middle Cambrian. Its formation lasted for about 70 million years. The fragments of the back-arc basin are confined to the Middle Paleozoic Charysh-Terekta-Ulagan-Sayan suture-shear zone, formed as a result of the subduction of the oceanic crust of the back-arc basin beneath the Vendian-Cambrian Tannuola island arc of the Paleoasian Ocean.