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Abstract

UDC: 552.3:(550.42+550.93)(571.151)

PETRPLOGY AND ORE CONTENT OF HIGH-POTASSIC ADAKITE GRANITOIDS OF THE MAKARYEVSKY RANGE IN GORNY ALTAI

A. I. Gusev

The paper considers geological features, petrology, geochemistry, absolute age, and genesis of granitoids of the Makaryevsky geographical range in Gorny Altai. It envelopes the Chernoklyuchevsky, Sosnovsky, Ust’-Osinovsky, Shchemilovsky, Makaryevsky and other massives. Five phases were singled out which include gabbroids, tonalites, trondhjemites, and leucogranites. The U-Pb age of granitoids was determined to be 349- 353 mln years, which is different from other rock extension areas of the Ust’-Belovsky complex. The massives structure is characterized by direct zonation with the early phases localized peripherally and the later phases in the middle. Granitoids were foliated. According to petrogeochemical data, felsic varieties have features of high-silica adakite granitoids. Gabbroids of the early phase of the Makaryevsky range were probably generated by partical melting of the slab represented by fluid-metasomatized mantle peridotite. And the later derivates originated by mixing of basite and adakite parent magmas. Generation of high-silica adakites is due to direct melting of the subducted oceanic crust which had been transformed into amphibolites and eclogites during subduction. Adakite granitoids of the Makaryevsky range were derived from partial melting (of about 50 %) of 10 % garnet amphibolite. High saturation of melts by fluids resulted in transformation of ratios of many elements with the appearance of tetradic effect fractionation of the M- and W-type rare earth elements. The scarn- and vein-type gold and copper occurrences are connected with the Makaryevsky range granitoids spatially and paragenetically.

Key words: gabbro, diorites, tonalites, trondhjemites, leucogranites, high-silica adakites, high-potassic adakites, tetradic effect fractionation of rare earth elements, gold mineralization.