Structure and Petrological-Geochemical Characteristics of Rocks of the Kabak-Taiga Ophiolite Complex of the Altai-Sayan Folded Region (Mountain Altai)

The Kabak-Taiga ophiolite complex is represented by serpentinite melange, including blocks of gabbro-pyroxenite-ultramafic and gabbro-diabase, intruded by leucoplagiogranite dikes. The melange is located at the base of the accretionary complex composed of tectonic sheets of basalts and rhythmically layered terrigenous and siliceous rocks altered in the greenschist facies of metamorphism. It was revealed that the gabbro-diabases belong to low-titanium tholeiites, the leucoplagiogranites are calcic and belong to M-type granites, and the basalts belong to moderately alkaline high-titanium volcanics. The microelement composition of the gabbro-diabases and basalts, as well as features of the composition of chromespinelides from ultrabasic rocks, indicates their formation during spreading in the back of the island arc. The set of new geological and petrological-geochemical data obtained on the rocks of the Kabak-Taiga ophiolite complex and basalts of the accretionary complex allows us to combine them into a single ophiolite association. Together with the ophiolites of southern Tuva, they represents the Vendian-Cambrian back-arc basin of the Tannuol island arc, fragments of which have been preserved in the Early-Middle Paleozoic Charysh-Terekta-Ulagan-Sayan suture-shear zone. The new obtained data are an important aspect in substantiating the geodynamic nature of the global suture-shear zone dividing the Altai-Sayan folded region into two large tectonic segments represented by collisional and accretionary orogens on the southern framing of the Siberian paleocontinent.