A Review of Conduit-Related Ni-Cu-(PGE) Sulfide Mineralization at the Voisey’s Bay Deposit, Labrador, and the Eagle Deposit, Northern Michigan
Edward M. Ripley, Chusi Li, 2011. "A Review of Conduit-Related Ni-Cu-(PGE) Sulfide Mineralization at the Voisey’s Bay Deposit, Labrador, and the Eagle Deposit, Northern Michigan", Magmatic Ni-Cu and PGE Deposits: Geology, Geochemistry, and Genesis, Chusi Li, Edward M. Ripley
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Mafic to ultramafic intrusive systems necessarily contain "conduits" through which magma has passed enroute to shallow levels of the crust. It is now commonly accepted that conduit systems are key sites for the accumulation of immiscible sulfide liquid and the generation of Ni-Cu-(PGE) deposits. Deposits such as those of Voiseys Bay in Labrador and Eagle in northern Michigan illustrate that sulfide deposits may form in both near vertical and horizontal portions of conduit systems. Although the Voisey Bay deposit is considerably larger than that associated with the Eagle intrusion, there are important similarities that emphasize the role of magma conduits in localizing sulfide mineralization. in addition to the similarities related to the physical collection of dense sulfide liquid, both deposits occur in provinces where anorthosites and early-stage picritc magmatism (Nain Plutonic Suite and the Midcontinent Rift system) are key elements of geochemical development. Geochemical evidence for the contamination of mafic magma by country rocks exists at both Voiseys Bay and Eagle. Conduit systems such as those of Voiseys Bay and Eagle provide an environment for enhanced magma-country rock interaction that may trigger the attainment of sulfide saturation of passing magma and initiate the ore-forming process.