Geologicheskii Vestnik

In the northern part of the Chebarkul-Bugodak monocline (Southern Urals), between the lakes Bolshoy Bugodak and Malyi Bugodak, thin sills were discovered, united in the Bugodak group of sills. They are the northernmost part of a single belt of Early Carboniferous sills extending for 200 km in the West Magnitogorsk zone. The dominant type of rocks of the Bugodak group are hornblende dolerites, but gabbrodiorites were also found, which indicates a multiphase origin of intrusions. Diverse zoning of clinopyroxene macrocrysts indicates variable conditions of melt crystallization at the early magmatic stage, associated with repeated injection of melts. The rocks were altered by hydrothermal fluids, which led to calcium and barium metasomatism. The chemical composition of gabbroids reflects the tholeiitic series nature with a subalkaline sub-type, which is typical for dolerites of the whole sill belt of the West Magnitogorsk zone. In terms of body thickness and material composition, the Bugodak sills are most similar to the sills of the Khudolaz area, which are of early Tournaisian age.

sills, mineralogy, geochemistry, petrogenesis, dolerite

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