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| TSX: DM | Last: $2.15 | Change: +0.05 | Volume: 176913 | ||
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| Projects Overview The Nokomis Deposit Project Summary The Duluth Complex |    An Emerging Major Copper-Nickel-Platinum-Palladium-Gold CampGeology of the Duluth Complex The Duluth Complex is a large, composite mafic intrusion in northeastern Minnesota that extends about 240 km northeast from Duluth Minnesota to the Canadian border. The Duluth Complex lies within Precambrian shield rocks of the Superior Province which include Archaean mafic to felsic volcanic rocks, greywackes, granitic intrusives and older ortho- and paragneisses. The Duluth Complex was intruded beneath a similar age volcanic rocks during the formation of the Midcontinent Rift System which developed approximately 1.2 to 1.1 billion years ago. The fill associated with the active stages of rift development consists mainly of tholeiitic basalt that was erupted under subaerial conditions, together with petrologically related sills, dikes, and large layered intrusions that cooled beneath or within the cogenetic volcanic pile. The largest and most important of the layered intrusions is the Duluth Complex, a composite intrusion of troctolite and gabbro derived from periodic tapping of an evolving magma source. In the waning stages of rifting, the principal rock types deposited in the rift shifted gradually from magmatic to sedimentary; among the sedimentary sequences are those for which alluvial-fan, fluvial braid-plain, aeolian, and lacustrine depositional environments may be inferred. Associated gabbroic intrusion resulted in the composite, arcuate, NE-SW elongated, 450 x 100 km Duluth Complex, which formed from up to 40 separate sheet like and cone shaped sub-intrusions and covers an area of approximately 6500 square kilometers. The copper -- nickel mineralization in the Duluth Complex rocks occurs in magmatic sulphide deposits. Magmatic sulphide deposits are sulphide mineral concentrations in mafic and ultramafic rocks formed from sulphide liquids, exsolved from the magma. Once formed, the droplets of sulphide liquid settle through less dense magma. The sulphide liquid acts as a "collector" for copper, nickel, cobalt and platinum group elements (PGEs) because these elements prefer the sulphide liquid to the magma by a factor of 10 to 100,000 times more. The combination of physically concentrating dense sulphide liquids and chemically concentrating elements in the sulphide liquid is responsible for forming most economically mineable magmatic nickel-copper sulphide deposits, like those found in the the Sudbury Complex in Canada, the Stillwater Complex in the U.S. and the Noril'sk-Talnakh Complex in Russia. The Duluth Complex hosts three distinct types of magmatic sulphide copper -- nickel mineral deposits. The deposit types include (1) large, low-to-medium grade, disseminated Ni-Cu concentrations, some of which contain local zones enriched in platinum-group elements (PGEs); (2) localized high-grade lenses and zones of massive Ni-Cu sulfides, some of which are moderately enriched in PGEs; and (3) stratabound PGE-enriched "reefs" associated with specific types of phase-layer transitions. Deposit types (1) and (2) occur only at or very near the basal contact of the Complex, whereas type (3) occurs in the basal zone and also at higher levels. At this time, large resources of low-medium grade copper-nickel sulfide mineralization that locally contain anomalous PGE concentrations are well documented by drilling in the basal zones of the Partridge River and South Kawishiwi intrusions. At least nine deposits have been delineated in the basal 100 to 300 meters of both intrusions. The mineralization consists predominantly of disseminated sulfides that collectively constitute over 4.0 billion tonnes (4.4 billion tons) of material averaging 0.66% Cu and 0.20% Ni. Summarized from MGS, UM (Miller et. al., 1998, Miller et. al, 2002, and Severson, 2005) and NRRI Information (Jirsa et. al.) |
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