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UDC 552.3:550.4:550.42:550.93
PETROLOGY AND ABSOLUTE AGE OF THE TOPOLNINSKY GABBRO-GRANODIORTE-GRANITE COMPLEX OF THE GORNY ALTAI
A. I. Gusev, N. I. Gusev, M. A. Kukoeva
The paper considers petrographic, petrological, geochemical features, an absolute age and genesis of granitoids of the Topolninsky complex in the Gorny Altai. Two massives were characterized in the area: Topolninsky and Karaminsky. Five phases were discovered, which are gabbro-diorites, quartz diorites, granodiorites, leucocratic granite-porphyry, with their petrographic descriptions, mineral and chemical composition given in the paper. Concordant ages of the clinopyroxene-biotite granodiorites of the main phase were received in the Topolninsky massif in 10 sites (397,4±4,4 m. y.) and the Karaminsky massif (399,3±4,6 m. y.), which correspond to the boundary between the Lower and Middle Devonian. The paper describes the normal direct zonation of the Karaminsky massif structure, where more evolved rock phases (granites, leucogranites) are localized in the central part of the intrusive rocks, and less evolved, initial rock phases (gabbroids, diorites) have a peripheral position. The Topolninsky rocks correspond to melting of amphibolites and garnet amphibolites at experimental plots. A number of features imply a more oxidized melt in the Topolninsky massif and more reduced one in the Karaminsky massif. Strontium isotope ratios and rare elements point at mixing of mantle magma and crust material.
Key words: petrology, petrogeochemistry, granitoids, absolute age, melting of amphibolites and garnet amphibolites, mantle-crust relation.
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