Geologicheskii Vestnik

The article describes the geological structure of the Yelanchik migmatite-gneissogranite massif located in the southern part of the Ilmenogorsk-Sysertsky block. It is composed of granitoids, the formation of which took place in two stages: in the first of them migmatites and gneiss-granites were formed, and in the second — biotite, muscovite and bi-mica granites. The massif lies among the metamorphic rocks of the Yelanchik and Kyshtym strata in the area of the lake Big Yelanchik. Based on the study of garnet-biotite paragenesis, comprehensively studied experimentally and widely represented in the granitoids of the Yelanchik massif, the formation temperatures of gneiss-granite (530– 550°С) and gneiss-biotite granites (540–560°С) were obtained, as well as the formation depth of rocks, corresponding to the near-surface or hypabyssal zones (first kilometers). The obtained data on the physicochemical conditions of formation of rocks of the massif made it possible to conclude that they are metasomatic in nature and exclude the magmatic genesis. Practically all analyzes of granitoids of the 1 and 2 stages of the formation of the Yelanchik massif (migmatites, gneiss-granites, biotite, bi-mica and muscovite granites) fit into the main calc-alkaline trend (CA) and are located within either calc-alkaline or subalkaline fields. Migmatites and gneiss-granites of the first stage of formation of the massif to the tungsten-molybdenum (W-Mo) and molybdenum (Mo-Cu) metallogenic trends. Of the greatest interest on tungsten mineralization are migmatites, and on molybdenum — gneiss-granites. The bi-mica granites of the second stage do not form a distinct trend and their metallogenic specialization is not defined. All analyzes of biotite and muscovite granites also show W-Mo metallogenic specialization.

Yelanchik massif, granites, migmatites, gneiss-granites, biotite-garnet thermometer, metallogenic specialization

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