—The Bayan-Kol gabbro–granite association has been recognized within the West Sangilen fragment of collision zone in the northwestern framing of the Tuva–Mongolian massif, and its composition, age, and tectonic and geodynamic settings have been studied. The association includes the Bayan-Kol pluton and composite (mingling) dikes, which formed in the late collision period (495 ± 5 Ma), during the transition from transpression to extension mode with left-lateral strike-slip kinematics. The Bayan-Kol gabbro–granite association is spatially confined to the penetrating tectonic zones of the West Sangilen shear system. The position of gabbroid and granite bodies is controlled by local zones of tectonic extension. Basic magmas have a similar petrogeochemical composition, which indicates their intrusion from a single chamber of basic composition and differentiation of ascending magma. The melting, transfer, and formation of crustal granitoids of the Bayan-Kol association are genetically related to the thermal effect of basic melt and a syntectonic drop in lithostatic pressure. The intrusion and formation of basic and acid melts of the Bayan-Kol association took place at the lower and middle crustal levels in the settings of the reactivation and subsequent fragmentation of the tectonic zone.

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