Platinum-group minerals from the McBratney PGE-Au prospect in the Flin Flon Greenstone Belt, Manitoba, Canada

The McBratney high-grade PGE-Au occurrence (up to 31 g/t Pd and 9 g/t Pt) is hosted by brecciated mafic-ultramafic volcanic rocks of the Bear Lake mafic unit in the vicinity of pyroxenitic-gabbroic intrusions in the Proterozoic Flin Flon greenstone belt. Manitoba. The occurrence comprises veins of massive sulfide with variable amounts of quartz, carbonate, clinochlore, chamosite, biotite, muscovite and a variety of platinum-group minerals. The Sulfides are mainly chalcopyrite, pyrrhotite, pyrite, with minor violarite, pentlandite, nickeloan pyrite, marcasite, sphalerite, galena, millerite and cobaltite-gersdorffite. Magnetite, coloradoite, and Au-Ag alloy occur locally. The platinum-group minerals (PGM) include, in order of abundance: borovskite [(Pd2.6Ni0.35Fe0.12)(Sigma3.07) (Sb1.06Bi0.06)(Sigma1.12) Te-3.81)], telluroan sudburyite [(Pd0.97Ni0.01Fe0.02Hg0.01)(Sigma1.01) (Sb0.78Te0.21)(Sigma0.99)], an unknown Pd telluride-antimonide [(Pd1.72Ni0.23Fe0.07)(Sigma2.02)(Te1.94Sb1As0.02)(Sigma2.94)], sudburyite [(Pd0.94Ni0.01Fe0.01Hg0.03)(Sigma0.99) (Sb0.95Te0.06)(Sigma1.01)], sperrylite [(Pt0.94Ag0.01Ni0.01Fe0.09)(Sigma1.05)As-1.95], temagamite [(Pd2.84Ni0.15Fe0.12)(Sigma3.11)Hg-0.93(Te2.60Sb0.35)(Sigma2.95)] and merenskyite [(Pd0.97Ni0.01Co0.01Fe0.07)(Sigma1.06)(Te1.85Sb0.08Bi0.01)(Sigma1.94)]. They are commonly found as inclusions in chalcopyrite, pyrite and carbonate. and are partially replaced by cobaltite-gersdorffite. Mineralogical and textural evidence suggests that the mineralization is hydrothermal, and later than the regional metamorphic event. The PGM precipitated coevally with the Ni-Fe-Cu sulfides, chlorite-chamosite, biotite, carbonate and quartz at temperatures below 500degrees-550degreesC.