HYPERGENE SULFATES OF THE ROZENITE GROUP OF THE SHERLOVOGORSK TIN-POLYMETALLIC DEPOSIT OF TRANSBAIKAL KRAI

Hypergene sulfates are prevalently received due to oxidation of sulfide-bearing rocks and ores that form the walls of the pit and storage of washery refuse. They are formed as powder, cryptocrystalline masses, hairlike and needle crystals; they often have ocher colors due to the presence of iron oxides and hydroxides. Minerals are hydrated sulfates of divalent metals: iron, magnesium, copper, zinc, cobalt, nickel, manganese. The rozenite group minerals: starkeyite, rozenite, boyleite, aplowite, ilesite, were taken for research. Their simplified formula is Me2+SO4.4H2O, wherein Me2+: Fe, Mg, Zn, Mn, Co. The actual composition of mineral individuals differs from the theoretical formula, there is isovalent substitution of cations. Besides Mg, Fe, Zn, Mn, and Co, the composition of minerals may also include Cd, Ni, Ca, Cu. There is unlimited isomorphism. The difference of electronegativity 0.4 and 15 % difference in atomic radius are limited to the area most favorable for the formation of solid solutions. For each cation in the mineral isomorphic elements are identified, divided into groups according to the potential to form wide or continuous solid solutions of substitution, according to calculations. The composition is given and empirical formulas calculated of starkeyite, boyleite and rozenite from the Sherlovogorsk deposit. Thermograms of the studied sulfates show two-stage dehydration of water in the temperature range from 50 to 400 degrees C. The sulfates are water migrants due to their high solubility. Besides isomorphic elements, other elements: Al, Ba, Be, Bi, Cl, Cr, Cs, Mo, F, Sb, Pb, Sn, As, V, W, REE, etc. are involving in the migration stream. The content of many elements in the samples exceeds the percentage abundance of crust by several times (in descending order): Cd, Zn, Bi, Se, S, Te, U, W, Yb, Cu, Ni, Mn, Y, Be, Co, Dy, Er, Gd, Ho, In Sm, As, La, Li, Mg, Pb, Mo, Nd, Tb. Cadmium is closely connected with zinc; both in sphalerite and in hypergene mineral formations it is an isomorphic impurity. The ratio of water migration of cadmium indicates average migration intensity, in contrast to zinc coefficients with very strong migration intensity. Migration intensity in this case can be regarded as accumulation intensity. Then, by evaporation of a sulfate reservoir, cadmium concentration in the residual solution grows exponentially. The devitrification of such a solution would lead to the formation of zinc-containing analogs of cadmium sulfates. Cadmium and above indicated elements exceeding the percentage abundance of crust have a serious ecological impact on the environment, as a deposit is in the culminating stage of its development when there is a maximum number of sulfates, which are concentrators of many toxic chemical elements and involve them in the migration stream.