TOURMALINE AS AN INDICATOR OF TIN OCCURRENCES ОF CASSITERITE-QUARTZ AND CASSITERITE-SILICATE FORMATIONS (A CASE STUDY OF THE VERKHNEURMIYSKY ORE CLUSTER, FAR EAST)

The research focused on the composition of tourmaline from tin ore deposits and ore occurrences within the Verkhneurmiysky ore cluster in the Amur region. The aim of the study is to determine the indicative signs of tourmaline from cassiterite-quartz and cassiterite-silicate formations. This research is based on the materials of a long-term study of the mineralogy of the Far East deposits, conducted at the Mining University under the scientific supervision of Professor Yu.B.Marin. The relevance of the study involves predicting of tin and associated mineralization. For the first time, SIMS and Mössbauer spectroscopy were used to study tourmaline from this region. We identified the typomorphic characteristics of the tourmaline composition, which are proposed to be used as indicators of tin-ore deposits. Typomorphic characteristics of tourmaline from cassiterite-quartz formation: schorl (Mg/(Mg + Fe) = 0.06) with a high content of Al and K; Fe3+/(Fe3+ + Fe2+) = 0.03; ZFe3+ = 1 %; impurities: Nb, LREE (La, Ce, Pr), Be, Bi, F, Li, and Mn; LREE content > 9 ppm; positive Gd anomaly. Typomorphic characteristics of tourmaline from cassiterite-silicate formation: schorl-dravite (Mg/(Mg + Fe) = 0.22) with a high Ca content; Fe3+ / (Fe3+ + Fe2+) = 0.17; ZFe3+ = 9 %; impurities: Zr, Y, Cr, V, Sn, In, Pb, W, Mo, Ti, HREE, Eu, Sr, Sb, and Sc; the content of Y is > 2 ppm, of HREE is > 3 ppm, Eu is > 0.1 ppm. The formation conditions of the cassiterite-silicate ore mineralization were more oxidizing than those of the cassiterite-quartz one. Tourmaline, formed under oxidizing conditions, contains such impurities as Sn, In, Nb, Bi, Sc, and LREE. The content of Sn isomorphic impurity in tourmaline reaches 8000 ppm.