Threading the Eye of the Needle: Lessons from the Search for Another Voisey’s Bay in Labrador, Canada
2000; Volume: 95; Issue: 4 Linguagem: Inglês
10.2113/gsecongeo.95.4.725
ISSN1554-0774
Autores Tópico(s)Indigenous Studies and Ecology
ResumoResearch Article| June 01, 2000 Threading the Eye of the Needle: Lessons from the Search for Another Voisey's Bay in Labrador, Canada Andrew Kerr; Andrew Kerr Geological Survey of Newfoundland and Labrador, Department of Mines and Energy, P.O. Box 8700, St. John's, Newfoundland, Canada A1B 4J6 †Corresponding author: e-mail, akr@zeppo.geosurv. Search for other works by this author on: GSW Google Scholar Bruce Ryan Bruce Ryan Geological Survey of Newfoundland and Labrador, Department of Mines and Energy, P.O. Box 8700, St. John's, Newfoundland, Canada A1B 4J6 Search for other works by this author on: GSW Google Scholar Author and Article Information Andrew Kerr Geological Survey of Newfoundland and Labrador, Department of Mines and Energy, P.O. Box 8700, St. John's, Newfoundland, Canada A1B 4J6 Bruce Ryan Geological Survey of Newfoundland and Labrador, Department of Mines and Energy, P.O. Box 8700, St. John's, Newfoundland, Canada A1B 4J6 †Corresponding author: e-mail, akr@zeppo.geosurv. Publisher: Society of Economic Geologists First Online: 02 Mar 2017 Online ISSN: 1554-0774 Print ISSN: 0361-0128 Economic Geology Economic Geology (2000) 95 (4): 725–748. https://doi.org/10.2113/gsecongeo.95.4.725 Article history First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Andrew Kerr, Bruce Ryan; Threading the Eye of the Needle: Lessons from the Search for Another Voisey's Bay in Labrador, Canada. Economic Geology 2000;; 95 (4): 725–748. doi: https://doi.org/10.2113/gsecongeo.95.4.725 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyEconomic Geology Search Advanced Search Abstract Magmatic sulfide mineralization is present in three of the four compositional groupings in the Mesoproterozoic Nain Plutonic Suite and in compositionally similar Paleoproterozoic rocks. Anorthosite-hosted mineralization appears to be spatially linked to small gabbronorite bodies, where sulfide liquids separated from silicate magmas to variable degrees, depending on the wall-rock conditions. Sulfide metal contents are low (0.2–1.0% Ni) and the Ni/Cu ratio is variable, although sulfide Ni values remain fairly consistent within individual occurrences. Pyroxenite-hosted mineralization is essentially restricted to minor intrusions, and locally, has higher sulfide metal contents (up to 2% Ni) and less variable Ni/Cu. There are similarities between pyroxenite- and anorthosite-hosted mineralizations, and they may form part of a broad continuum. Ferrodiorite-hosted disseminated sulfide mineralization is associated with abundant iron oxides, and typically, has low amounts of Ni in the sulfide (<0.5%), and Ni/Cu <<1. Gabbro-troctolite–hosted mineralization contains the most variable and metal-enriched sulfides, containing from 1 to 7 percent Ni, and showing consistent Ni/Cu ≪1. The best examples are associated with the Voisey's Bay intrusion (dominantly troctolite) and the Pants Lake intrusion (dominantly olivine gabbro). Significantly, these are the only Nain Plutonic Suite mafic intrusions that were emplaced into or in close proximity to sulfide-bearing paragneisses; exploration of gabbroic and troctolitic rocks within Archean orthogneisses has not yet revealed significant mineralization. The Pants Lake intrusion has intriguing geologic similarities to the Voisey's Bay intrusion and supports some aspects of genetic models for the latter. However, it has lower sulfide Ni contents (around 2%) and relatively elevated Cu and Co, suggesting differences in the source magmas and/or conditions of sulfide segregation.The different styles of mineralization can be integrated with petrogenetic models for the Nain Plutonic Suite and similar plutonic suites. Anorthosite-hosted sulfide mineralization is interpreted to be derived from residual mafic magma that coalesced and migrated during ascent of semicrystalline anorthositic magmas, and ferrodiorite-hosted mineralization is interpreted to be derived from late Fe-enriched differentiates of deep-seated mafic chambers. In both cases, the source magmas were fractionated, which limits their potential for metals. Crustal sulfur from paragneisses may have played a role in sulfide saturation in both cases but does not appear to be a critical ingredient. Some pyroxenite-hosted mineralization is akin to anorthosite-hosted types, but other examples may be linked to silicic contamination of more mafic magmas. Gabbro-troctolite–hosted mineralization is associated with mafic magmas that rose from deep crustal chambers prior to extensive fractionation; these were richer in Ni, Cu, and Co when they ascended into the upper crust. Sulfide-bearing paragneisses apparently played a critical role in inducing sulfide saturation in the magmas. The lessons from the search for nickel in Labrador are mostly familiar from other areas; the regional metallogeny of the Nain Plutonic Suite underlines the critical roles of a relatively unevolved host magma and crustal contamination processes, possibly involving addition of externally derived sulfur. It emphasizes the importance of identifying and prioritizing these two key factors in the exploration of similar anorthosite-dominated plutonic suites elsewhere in the world. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
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