Whole rock geochemistry, mineral chemistry, petrology, and platinum, palladium mineralization of the Seagull Intrusion, northwestern Ontario

The Seagull Intrusion emplaced during formation of the 1.1 Ga Mid-continental Rift centred around Lake Superior was studied in several drill core and surface samples and consists of a lower ultramafic section (∼650 m) and an upper mafic section of unknown thickness (<100m). The lower ultramafic section is texturally dominated by cumulate olivine and poikilitic clinopyroxene with lithologies consisting of dunites, peridotites and pyroxenites. The upper mafic section is variable in lithology, with increasing upwards in abundance of cumulate pyroxene and poikilitic feldspar, dominated by olivine gabbro and gabbros.; Olivine, pyroxene and oxide mineral chemistry from the lower ultramafic section, indicates limited fractionation throughout the section. Olivine compositions from the mafic section exhibit a more differentiated nature and range in composition from Fo57.4 to Fo75.8.; Whole rock geochemistry is consistent with the homogeneous nature of the ultramafic section and more differentiated character of the mafic section.; Platinum, palladium, nickel and copper mineralization is found at the base of the ultramafic section of the intrusion, formed during initial emplacement and sulphur saturation at that point in time. (Abstract shortened by UMI.)...