Mineralogy of W-Pb-Bi ores from Rudnik Mt., Serbia

Abstract

Polymetallic W-Pb-Bi ores have been found in the Nova jama ore zone of Rudnik Mt., Serbia. They are situated on the contact of quartzlatite dykes and breccias; mostly occur in a stockwork-type form. In this ore zone three mineralization phases can be distinguished: pyrometasomatic (skarn), pyrometasomatic-hydrothermal and hydrothermal. The pyrometasomatic-hydrothermal phase is the most significant mineralization phase because it is represented by massive ore bodies. They contain a wide variety of minerals including significant amounts of scheelite, native bismuth and sulphosalts, mostly presented by Pb-Bi-sulphosalts. Mo-free scheelite, the only tungsten bearing mineral, was found in economically interesting amounts. Energy Dispersive Spectrometry (EDS) analyses yielded the empirical formulae: Ca0.98WO4 for scheelite, Pb0.99S for galena, (Pb1.91Ag0.05Cu0.08)(2.04)Bi1.93S5 for cosalite and (Pb0.98Ag0.03Cu0.05)(1.06)Bi1.99S4 for galenobismutite. Tetragonal unit-cell parameters for scheelite amount to a = 5.24291 (6), c = 11.3738 (2) angstrom, V = 312.644 (7) angstrom(3). Atomic coordinates, isotropic displacement parameters, interatomic distances, and angles of scheelite were refined from X-ray powder diffraction data using the Rietveld method. Orthorhombic unit-cell parameters were calculated from single crystal data for cosalite to a = 19.13 (1), b = 23.64 (5), c 4.070 (3) angstrom, V = 1839 (5) angstrom(3) and for galenobismutite to a = 11.743 (3), b = 14.525 (8), c = 4.087 (8) angstrom, V = 696.0 (7) angstrom(3).