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UDC (552.3:550.42):551.734(571.151) GEOCHEMISTRY AND PETROLOGY OF THE BOROVLYANKA COMPLEX ROCK TYPES, GORNYI ALTAI
The article considers petrography, petrology, geochemistry and genesis of the Borovlyanka Late Devonian granitoid complex. Four stages of intrusion are distinguished and evidences for the existence of independent stage of leucogranites possessing a signifi cant metallogenic importance are given. Early intrusion stages have been formed due to the melting of amphibolites and greywackes. Geochemical data indicate that diorites and granodiorites have been generated as a result of melting of mantle substrates containing garnet. Fractionated leucogranites of the fi nal stage have been formed owning to the melting of pelites and assimilation of pelitic crust material. The complex rocks are characterized by two types of tetradic effect of rare-earth elements fractionation: W- and M-types resulting from diverse fl uid regimes and water and hydrofl uoric acid. Decrease in tetradic effect of W-type is accompanied by weak increase of Eu/Eu* ratio. They reveal non-CHARAC behavior of rare and rare-earth elements. According to the set of features leucogranites are potentially promising for rare-metal and rare-earth mineralization.
Key words: petrology, petrogeochemistry, granitoids, fractionated leucogranites, tetradic effect of rareearth elements fractionation.
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