New Pd-Pb and Pb-V oxides from a bonanza-type PGE-rich, nearly BMS-free deposit in the Penikat layered complex, Finland

The Kirakkajuppura platinum-group-element (PGE) deposit, in the Penikat layered complex, Finland, is associated with the low-sulfide Sompujiirvi PGE reef, located near the contact between ultramafic and gabbroic cumulates, close to the country rocks. The deposit is unique among PGE deposits in layered intrusions as it displays, on a relatively small scale, very high bulkrock concentrations of PGE (up to >0 5 kg/t total PGE) aLong with a low content of S and Cr, e.g.,\fcn 224 ppm. 108 ppm S and 0.8 wt.% Cr; (Pd + Pt)/(Os + Ir + Ru) = 93.9 and Pd/ft = 3.0 (mean of four whole-rock analyses). The platinum-group minerals (PGM), predominantly Pt-Ni-poor vysotskite-braggite, zvyagintsevite and a Pd-Pb oxide, mainly occur in altered pyroxenite, among grains of Mg-rich actinolite and clinochlore, as unusually large veinlerlike or chain-like aggregates up to -1 cm in length. In agreement with the whole-rock data, the PGM do not show a close relationship with base-metal sulfides (8M,9) and accessory chromite, occur in virtually BMS-free chromite-poor samples, and are mainly responsible for the bulk-rock S. Unnamed PdePbOlg is the product of oxidation of the zvyagintsevite. It is anhydrous, is a very poor diffractor of X rays [the shongest two lines arc 2.69(l0vb1and 2.35(3) Al, anO trai a low reflectance (ai SaO nm in air: k, ZO.Z-ZO.I% and ni Z0.621 3%o).Unnamed PbaV2Oe also occurs in the hydrous silicate association. The Kirakkajuppura PGE deposit cannot have formed as a result of the collection of the PGE by a magmatic sulfide liquid in situ. Tlrclate-stage PGM, responsible for the high PGE concentration in this deposit, precipitated from a hydrothermal fluids