Mineralogical Composition and Geochemical Features of Alluvial Deposits of the Lower Riphean Bolshoy Inzer and Suran Formations (South Urals)
This paper considers the results of mineralogical and geochemical studies on alluvial deposits of the Bolshoy Inzer (Bzyak Rivulet) and Suran (Karaelga Rivulet) Formations, the outcrops of which are confined to the Yamantau Anticlinorium, the largest structure of the Bashkir Meganticlinorium. The mineralogical composition of the deposits includes quartz (prevailing), feldspars, epidote, kaolinite, muscovite, dolomite and accessory minerals (goethite, hematite, rutile, titanite, magnetite, pyrite, monazite, fluorite, zircon). Titanite (about 1%) is predominant among the accessory minerals in the Bolshoy Inzer Formation. Goethite, rutile and zircon (in descending order) are found to a lesser extent. The dominant accessory mineral in the Suran Formation is goethite (about 5%); hematite, rutile, titanite, magnetite, pyrite, monazite, fluorite and zircon (in descending order) occur less often. Judging from geochemical analysis, the samples are characteristic of relatively high Zr contents. It is for the first time that gold was discovered in the alluvial sediments of the Karaelga Rivulet. Here, gold shows a relatively high fineness (about 940) and an Au/Ag ratio of 16.5 on average. This is somewhat different from the gold composition in primary deposits and ore occurrences of the Avzyan Ore Field in the Yamantau Anticlinorium. Finding gold to the north of the known gold-bearing placers of the region dictates the need for further research. Also, there are relatively high Co, Cr, Ni, Zn, Pb, Y and REE concentrations comprising about 600 g/t in total. Apatite and monazite фre the most probable minerals to concentrate lanthanides.