Age and Geodynamic Position of Ophiolites of Kurtushiba Ridge of Western Sayan

The composition of metadiabase dikes, metabasalt lavas, and plagiogranite veins of the ophiolite association in the upper reaches of the Koiard River of the Kurtushiba Ridge has been studied. The results of the geochemical studies have shown that these ophiolites are characterized by an N-MORB+IAB–like composition. The U–Pb age of the ophiolites is 569 ± 6 Ma. The ophiolites of Kurtushiba Ridge, along with the ophiolites of the Shatskii massif in Western Tuva and the island-arc complexes of the Ondum subzone, were formed simultaneously or close in time, ~578–569 Ma, at the early evolutionary stage of the Tannuola–Khamsara paleo-island arc.