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TitleUnravelling the Western Churchill province paleoproterozoic gold metallotect: constraints from Re-Os arsenopyrite and U-Pb xenotime geochronology and LA-ICP-MS arsenopyrite trace element chemistry at the BIF-hosted Meliadine Gold District, Nunavut, Canada
AuthorLawley, C J M; Creaser, R A; Jackson, S; Yang, Z; Davis, B; Pehrsson, S; Dubé, B; Mercier-Langevin, P; Vaillancourt, D
SourceEconomic geology and the bulletin of the Society of Economic Geologists 2014 p. 1425-1454, https://doi.org/10.2113/econgeo.110.6.1425
Year2014
Alt SeriesEarth Sciences Sector, Contribution Series 20140436
PublisherSociety of Economic Geologists
Documentserial
Lang.English
Mediapaper; on-line; digital
File formatpdf
ProvinceNunavut
NTS45D; 45E; 45L; 45M; 46D; 46E; 46L; 46M; 55; 56; 65; 66
Areawestern Churchill Province
Lat/Long WENS-104.0000 -86.0000 68.5000 60.0000
Subjectseconomic geology; geochemistry; igneous and metamorphic petrology; metallic minerals; craton; greenstone belts; metamorphism; plutons; fracture filling deposits; fracture zones; fractures; deformation; chalcopyrite; arsenopyrite; galena; gold; isotopes; hydrothermal alteration; mass spectrometer analysis; mineral deposits; sulphide deposits; radiometric dating; hydrothermal deposits; remobilization; trans-Hudson Orogeny; Banded Iron Formations; LA-ICP-MS; Archean; Post-Archean; Meliadine gold district; Proterozoic
Illustrationslocation maps; structural cross-sections; tables; photographs; photomicrographs; graphs
ProgramGold Ore Systems, Targeted Geoscience Initiative (TGI-4)
Released2015 07 13
AbstractThe gold endowment of the Western Churchill Province is conventionally attributed to reworking and attendant metamorphism during the Trans-Hudson Orogeny (1.9-1.8 Ga). The Meliadine Gold District is regarded as a type example of this inferred Paleoproterozoic Gold Metallotect and also represents one of Canada-s largest emerging orogenic greenstone- and Banded Iron Formation (BIF)-hosted gold districts (2.8 Moz contained Au in reserves and total resources of 5.8 Moz Au). The largest gold deposits are co-spatial with the Pyke Fault and associated quartz (± ankerite) veining, which cuts Neoarchean (ca. 2.66 Ga) supracrustal rocks comprising the Rankin Inlet greenstone belt. Gold in the Meliadine gold district occurs as inclusions within idioblastic arsenopyrite crystals, at sulfide crystal boundaries and/or as sulfide fracture fills within hydrothermally-altered, sulfidized and veined BIF. Clusters of gold, Bi-Mo tellurides, chalcopyrite, and galena inclusions characterize high-grade ore zones and are spatially associated with sieve-textured and variably recrystallized arsenopyrite domains. These micro-textural relationships suggest that incipient sulfide recrystallization liberated gold, which along with other precious- and base-metals, were redistributed into low-strain sites during late fluid-assisted and deformation/metamorphic-driven remobilization. Late gold enrichment is also demonstrated by LA-ICP-MS arsenopyrite mapping. Hydrothermal xenotime is co-spatial with gold and yield U-Pb ages at ca. 1.86 Ga. This hydrothermal event is synchronous with, or post-dates, arsenopyrite recrystallization and suggests that gold remobilization was concomitant with the Tran-Hudson Orogeny. New Re-Os arsenopyrite model ages range from 2.3-1.8 Ga and document a hitherto unrecognized pre-1.86 Ga hydrothermal activity and sulfide mineral formation history. The range of Re-Os model ages tends to support partial open-system behavior and/or mixing of disparate arsenopyrite generations that are evident from micro-textural observations and in situ LA-ICP-MS element mapping. Replicate analyses of the two most rhenium-rich and homogeneous arsenopyrite samples yield Re-Os model ages at ca. 2.27 and 1.90 Ga, which are broadly concurrent with the Arrowsmith (2.4-2.3 Ga) Orogeny and the earliest phase of the Tran-Hudson Orogeny (known locally as the Snowbird Orogeny; ca. 1.9 Ga), respectively. These rhenium-rich samples are also gold-poor and likely yield ages that pre-date remobilization and subsequent enrichment along arsenopyrite crystal boundaries and fractures. We speculate that gold was initially introduced at 2.27 Ga and/or 1.90 Ga along with arsenopyrite and was subsequently remobilized, coupled with arsenopyrite recrystallization, during the later stages of the Trans-Hudson Orogeny at 1.86 Ga. If correct, these new ages imply that the Paleoproterozoic Gold Metallotect, which is recorded across the Western Churchill Province, in fact, comprises multiple temporally-distinct gold events. Differentiating between disparate Paleoproterozoic gold events represents a critical step for effective mineral exploration in the Western Churchill Province and other reworked Archean terranes.
Summary(Plain Language Summary, not published)
The Targeted Geoscience Initiative (TGI-4) is a collaborative federal geoscience program that provides industry with the next generation of geoscience knowledge and innovative techniques to better detect buried mineral deposits, thereby reducing some of the risks of exploration. The timing of gold impacts mineral exploration strategies. This contribution reports new age dating results for the Meliadine gold district, Nunavut. These results leads to a revised mineral deposit model and links gold to the regional geologic history in Nunavut.
GEOSCAN ID295828