Jeff Myllyaho HBSc thesis abstract

The Bird River Sill is an approximately 600 metres thick, layered ultramafic and mafic intrusion that is intermittently exposed over a strike length of approximately 20 kilometres in southeastern Manitoba, Canada.  Continental arc and intra-arc, rift-related magmatism occurred from 2.75-2.73 Ga and resulted in the intrusion of the Bird River Sill into the Rice Lake Group of the Archean Bird River Greenstone Belt (Sanborn-Barrie et al., 2001).  Initial interest in the mineral potential of the Bird River Belt resulted from the discovery in 1917 of nickel and copper sulphides in ultramafic rocks within the northern limb of the sill.  Economic interest in the sill has continued to the present with the main objective of this study being to determine if there any minerlogical indicators for nickel-bearing sulphide within drill core provided by North American Palladium Ltd. in the summer of 2005.

Petrology, X-ray diffraction (XRD) and scanning electron microscopy (SEM) shows that regional metamorphism in the Bird River area induced weak to strong alteration within certain ultramafic rocks.  Major alteration products include uralitization of pyroxene and serpentinization of olivine within peridotite intervals.  Clinochlore also commonly replaces ferromagnesium pyroxene and olivine in ultramafic.  Mineralized intervals from North American Palladium's 2005 drill holes showed increased abundances of actinolite and clinochlore.  Along with this increased alteration, the minor amount of remnant olivine crystals present in mineralized samples display a slightly rounded habit.  This contrasts with unmineralized, less altered intervals within the Bird River Sill.  These unmineralized intervals show slightly elongated and more abundant remnant olivine crystals.  Alteration between mineralized and unmineralized intervals also shows differences in the modal abundance of actinolite and clinochlore where there is decrease inabundance of both phases unmineralized sections.