Germanium-Rich Palladium Minerals Palladogermanide Pd2Ge, Paolovite Pd2(Sn, Ge), and Zvyagintsevite in Sulfide-Bearing Anorthosites of the Yoko-Dovyren Pluton, Baikal Area

Resumo

The bottom part of the Yoko-Dovyren layered mafic–ultramafic intrusion hosts the Baikalskoe deposit of Cu–Ni sulfide ores with Pt–Pd mineralization, and the stratigraphically higher portion of the intrusion includes units and pockets with low-sulfide ore with Pt–Pd mineralization. The maximum Pd, Pt, Au, Ag, Hg, and Cd concentrations and the greatest number of noble-metal minerals, including those containing Ge, are typical of vein-shaped sulfide-bearing anorthosite bodies and pegmatoid anorthosites in the upper part of the Critical Unit, at the boundary between the troctolite unit and overlying gabbronorite. The noble-metal minerals were produced mostly by postmagmatic pneumatolytic (fluid–metasomatic) processes. These minerals are kotulskite, moncheite, zvyagintsevite, telargpalite, paolovite, and other Pd and Pt chalcogenides and intermetallic compounds, including palladogermanide that contains 19.8 wt % Ge (the first find in Russia), paolovite with 8.1 wt % Ge (first find), and Au-rich zvyagintsevite that bears 0.55 wt % Ge. The palladogermanide has the composition Pd_2.03(Ge_0.80As_0.15Bi_0.02)_0.97, and much of its Ge is substituted for As, as is typical of endogenic Ge minerals. The composition of the Ge-paolovite is Pd_2.02(Sn_0.54Ge_0.35Sb_0.05As_0.04)_0.98. The possible source of the germanium is contact-metasomatic pyrite-bearing paralic carbonaceous shales hosting the intrusion.