Synkinematic granites and collision-sheer deformations in Western Sangilen(Southeastern Tuva)

By the example of the Naryn-Marat area (left bank of the Naryn River, Sangi len highland) it is shown that metamorphic rocks of the Teskhem-Mugur compl ex and overlapping Upper Riphean terrigenous-carbonate series exhibit shear -extensional deformations that occurred under ductile and beihle-ductile no w conditions. These deformations, caused by an oblique collisional compress ion of the crust in the Early Caledonian, resulted in a system of weakened zones (marble melange in the terrigenous-carbonate cover, subhorizontal sur faces of stripping (decollement), and subvertical zones (Ridel's)). Shear-e xtensional dislocations and related decollements were magma-controlling str uctures for sills of the Tannuol' diorite-quartz-diorite-granodiorite compl ex (451+/-15 Ma) and younger dike belts and vein series of the Chzhargalant granite-leucogranite-pegmatite complex (442+/-21 Ma). The composition of g ranite-leucogranites of this complex indicates their dual geochemical natur e. On the one hand, they have a plumasite composition with a predominance o f potassium, which makes them similar to S-type granites forming from a met apelite source, and, on the other, they inherit some geochemical features o f the Tannuol' dioritoids (deficit of Ta and Nb and enrichment in Sr and Ba ). A model is proposed according to which the formation of the Chzhargalant granite-leucogranites was caused by two independent factors: existence of a deep-seared chamber of andesitic magmas - a source of heat and fluids, an d shear-extensional deformations, leading to formation of local decompressi on areas in the roof, where fluids concentrated and nonequilibrium melting of metapelites occurred.