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PETROLOGY AND GEOCHEMISTRY OF TURMALINE LEUCOGRANITES OF GORNY ALTAI

A. I. Gusev, E. M. Tabakaeva

Shukshin Altai State Humanities Pedagogical University, Biysk, Russia

Data on petro-geochemistry, petrology and ore-bearing properties of tourmaline leucogranites of the Gorny Altai are presented. They are divided in 2 groups: 1 – leucogranites with association of minerals muscovite-biotite-tourmaline-quartz-feldspars (rarely garnets), and 2 – leucogranites with the association tourmaline-muscovite-quartz-feldspar, sometimes garnet. Tourmaline leucogranites of the region are referred to the peraluminous and ferruginous types of rocks. By age, they are also divided in 2 groups: 1 – Early Jurassic and Late Permian-Middle Triassic, and 2 – Early Devonian and Early Triassic. Reasons for their formation are given as follows due to the melting of peraluminous leucogranites, metagrauwacks and felsic pelites, and 2 due to the fractionation of basaltoid and andesitoid sources. In tourmaline leucogranites, two types of tetradic fractionation effect (TFE) of REEs are apparent: W and M. It is shown that the manifestation of both types of TFE of REEs and an increase in tungsten concentrations are associated with an increase in the medium acidity. Different types of W, Mo, Sc, U, Be mineralization are spatially and paragenetically related to massifs that have tourmaline leucogranites in their composition.

Keywords: tourmaline leucogranites, age groups, melting sources, tetradic fractionation effect of REEs of М- and W-types, medium acidity, Mo, Sc, U, Be.

DOI 10.20403/2078-0575-2018-2-39-48