Structural-Morphological Types and Localization Conditions of the Apocarbonate Talc Mineralization in the Beloretsk District of the Western Urals Province

The structural–morphological types and localization conditions of talc occurrences in the Beloretsk district of the Western Urals talc province are discussed. The talc mineralization is represented by low-iron talcites and talc stones in the Riphean clastic–carbonate complexes of the Bashkirian Meganticlinorium. Prospective talc objects in the Beloretsk district are classified as apocarbonate, to be distinguished from the apoultramafic deposits, which are predominant in the Urals. The hydrothermal–metasomatic genesis of the talc ores, their association with the metamorphosed dolomite-bearing members of the Lower and Middle Riphean Kyzyltash and Avzyan formations, the cooccurrence with magnesite deposits, and the absence of relationship with granitoid magmatism are established. The inner resources of the Riphean sedimentary basins, activated by metamorphic processes, are viewed as the sources of ore-forming fluids. The flanks of magnesite bodies in dolomite sequences near contacts with silicate interbeds are considered as the lithological settings favorable for talcite formation. The presence of the stacks of interbedded magnesian–carbonate and aluminosilicate rocks in the Riphean sequences facilitates the silica–magnesium bimetasomatism but leads to the formation of predominantly lean talc–chlorite stone varieties. The morphological types of mineralization are represented by the stratiform bed-like talcite and talc stone bodies; the saddle-like and ribbon-like talcite bodies confined to monoclines and fold hinges and limbs; and the fault controlled steeply dipping linear bodies of rich talc ores.