Mineralogical and Geochemical Evidence for Granite Metasomatism in Dikes in the North of the Berezovskoe Ore Field (Middle Urals)

摘要

We present results of petrographic, geochemical, and mineralogical studies of apogranite metasomatites associated with sulfide-quartz gold ore veins. The studies show a predominance of muscovite and quartz-muscovite metasomatites. Formation of muscovite metasomatites was accompanied by the accumulation of W, Sc, Zr, Fff, Ga, REE, U, Th, Ta, and Nb and the genesis of new accessory minerals: monazite-(Ce), apatite, zircon, scheelite, W-containing rutile, uraninite, thorianite, cassiterite, etc. Compared with the primary granites, quartz-muscovite metasomatites are richer in Pb, Bi, As, Sb, Co, Ni, Ba, In, Cd, Mo, Te, Ag, and Au (elements of the gold ore assemblage). The high contents of these trace elements are due to abundant galena, fahlores, chalcopyrite, and pyrite among the accessory' minerals. Metasomatism of granites was followed by the removal of SiO2, which was then spent for the formation of quartz veins. We have revealed that the distribution of metasomatites of different types within a dike body affects directly the distribution of sulfide-quartz veins and thus determines the ore content of the dike body fragments.