The McBratney PGE-gold occurrence, Flin Flon greenstone belt, Manitoba, Canada: Characterization of the host rocks and mineralized zones, and genetic model

The McBratney platinum-group element (PGE)-Au occurrence, located about 7 km east of Flin Flon, Manitoba, is very high grade, with up to 33 g/t Pt, 207 g/t Pd, and 75 g/t Au. Zones of high-grade PGE mineralization occur in sulfides or carbonate-, quartz- and chlorite-rich veins dominated by massive chalcopyrite and pyrrhotite, that cut the metamorphosed host rocks. Platinum-group minerals (PGM) found at McBratney include Pd-telluride-antimonides and a Pt-arsenide, which occur most commonly as inclusions within the sulfides. Minor PGM also occur within chlorite, carbonate and biotite, and Au-Ag alloy is observed locally included in Fe-sulfides in association with sphalerite. The other hydrothermal phases associated with PGM and sulfides are quartz, chlorite, chamosite, carbonate and stilpnomelane.; This geochemical and petrographic investigation reveals that the host rocks, chlorite schist and chlorite-actinolite schist, are more basic-ultrabasic in composition than previously reported, with probable protoliths of tholeiitic basalt and pyroxenitic komatiite, respectively. The identification of basic-ultrabasic units with komatiitic affinity within the Bear Lake basaltic andesite unit opens up the exploration potential for Ni-Cu-PGE massive sulfides within this and other similar units within the Flin Flon greenstone belt, in particular the Bear Lake block. Also, there are several recent reports of PGE occurrences from the Flin Flon greenstone belt, confirming the potential of the belt to host this type of deposit, but, to date, none has been studied in detail.; The structure, mineralogy, textures, geochemistry and chlorite geothermometry of the McBratney PGE-Au occurrence are indicative of a hydrothermal origin for the PGE mineralization. The precious metals may have been transported as bisulfide complexes and precipitated due to cooling and the formation of tellurides, antimonides and arsenides during the waning stages of the retrograde metamorphic event.