Nicopor Mine, Pays Plat Lake Area, Thunder Bay District, Ontario, Canada
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The deposit is classed as a 'mafic-ultramafic intrusion-hosted ' deposit. The prospect occurs at the northern contact of the Schreiber greenstone belt with the Crosman Lake granitic batholith. The greenstone belt assemblage consists of an east trending, homoclinal succession of mafic to felsic metavolcanic rocks intruded by sill like gabbro bodies. In the vicinity of the Nicopor prospect the massive amphibolite host had been largely interpreted by various exploration geologists as a metamorphosed and altered mafic to intermediate volcanic rock. Recent mapping, based to a large extent on comparison with other mafic rocks nearby, suggests that this amphibolitic unit is gabbroic rather than volcanic. This interpretation also accounts to some degree for the source of the nickel and copper rich sulphide mineralization as discussed below. Base metal sulphides occur as massive to vein like and net textured aggregates in a narrow, linear zone that follows the contact between a dark green, massive amphibolite (melagabbro) on the south and medium grained, equigranular, pink granite on the north. A quartz bearing, mafic rock typically occurs between the melagabbro and the granite and has been mapped as leucogabbro, possibly representing a hybrid phase between the two main host rocks. This mineralized zone has developed a conspicuous, extensive gossan that obscures host rock and sulphide relationships. White iron hydroxides and rare malachite have developed as stains on deeply weathered sulphides. Several shallow pits have been sunk on this northeast striking zone over a distance of approximately 75 m. The sulphide zone on surface ranges up to approximately 2 m in width and rapidly grades outwards into disseminated mineralization in both the gabbro and granite. The sulphide zone is crosscut by barren aplite, syenite and feldspar porphyry dykes.
12 entries listed. 9 valid minerals.
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Ontario Ministry of Northern Development and Mines MDI Number: MDI42D14NW00035