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TitleAge and geological setting of the Rankin Inlet greenstone belt and its relationship to the gold endowment of the Meliadine gold district, Nunavut, Canada
AuthorLawley, C J M; McNicoll, V; Sandeman, H; Pehrsson, S; Simard, M; Castonguay, S; Mercier-Langevin, P; Dubé, B
SourcePrecambrian Research vol. 275, 2016 p. 471-495,
Alt SeriesEarth Sciences Sector, Contribution Series 20150301
PublisherElsevier BV
Mediapaper; on-line; digital
File formatpdf; html
NTS45D; 45E; 45L; 45M; 46D; 46E; 46L; 46M; 47B/03; 47B/04; 47B/05; 47B/06; 47B/11; 47B/12; 47B/13; 47B/14; 47C/03; 47C/04; 47C/05; 47C/06; 47C/11; 47C/12; 47C/13; 47C/14; 55; 56; 57A; 57B; 57C; 57D; 65; 66; 67A; 67B; 67C; 67D
Lat/Long WENS-104.0000 -86.0000 70.0000 60.0000
Subjectsgeochemistry; geochronology; gold; Archean; greenstone belts; lithogeochemistry; uranium lead dates; lithostratigraphy; mineral deposits; zircon dates; volcanic rocks; turbidites; dykes; tonalites; granodiorites; conglomerates; volcanic rocks; petrogenesis; Churchill Province; Rankin Inlet greenstone belt; Meliadine gold district; Precambrian; Proterozoic
Illustrationslocation maps; lithographic cross-section; core logs; photographs; schematic cross-section; tables; stereonets; geochemistry charts; geochronology charts; photomicrographs; bargraphs
ProgramTargeted Geoscience Initiative (TGI-4), Gold Ore Systems
Released2016 01 23
AbstractArchean greenstone belts host a significant proportion of the world's gold, typically in deposits that formed late during greenstone belt formation and cratonization. However, this is not always the case and, in the multiply reworked western Churchill Province (wCP), orogenic lode gold deposition post-dates greenstone belt formation by nearly one billion years. The spatial link between Proterozoic gold and Archean greenstone belts in the wCP is thus particularly striking although its significance is still not fully understood. The Meliadine gold district (2.8 Moz contained Au in reserves, plus an indicated and inferred resources of 5.8 Moz Au) represents an important example of this deposit style and is hosted within the Rankin Inlet greenstone belt (RIGB), which occupies a critical, but controversial position along the largely inferred boundary between the Hearne craton and the Chesterfield block. RIGB felsic volcanic rocks (ca. 2.66 Ga) are structurally intercalated, and broadly coeval, with mafic volcanic and volcaniclastic rocks (2.66-2.64 Ga), turbidite (=2.66-2.64 Ga), argillite, auriferous banded iron formation successions and syn-volcanic granodioritic to tonalitic intrusions (2.67-2.64 Ga). Neoarchean basaltic to andesitic volcanic rocks possess calc-alkaline to primitive arc-like tholeiitic magmatic affinities along with lesser MORB-like basaltic compositions. Geochemically evolved lavas yield depleted 144Nd/143Nd ratios (epsilon-Nd 2.66 Ga = -1.1 to +1.6) that reflect variable interaction with an evolved and hitherto undocumented Meso- to Neoarchean basement underlying the RIGB, whereas transitional, arc-like primitive tholeiitic and MORB-like basaltic samples overlap with the Nd isotopic composition of depleted mantle at ca. 2.66 Ga (epsilon-Nd 2.66 Ga = +1.6 to +2.7). These Neoarchean volcano-sedimentary panels represent the main auriferous rock package within the Meliadine gold district and are intercalated with deformed Paleoproterozoic conglomerate (=2.50 and =2.155 Ga). The latter are, in turn, unconformably overlain by a geochemically distinct pillowed-basalt sequence and a unique carbonate-siliciclastic package that presumably represent the remnants of Paleoproterozoic basins and are not known to host gold. The geological setting of gold deposits thus likely reflects this favourable Neoarchean lithostratigraphy in addition to metamorphism and fluid focusing along the reactivated faults during the collision of the Hearne and combined Chesterfield block-Rae craton at 1.90-1.85 Ga.
Summary(Plain Language Summary, not published)
The Targeted Geoscience Initiative (TGI) 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. Metamorphosed volcanic rocks represent an important host for some of the world's largest concentrations of gold. TGI-4 is focused on improving models and targeting for these metamorphosed deposits. In this contribution, we report new field work and geochemistry results for a package of metamorphosed rocks near Rankin Inlet that host one of Canada's largest emerging gold districts (Meliadine). Our results allow us to evaluate the key controls on the distribution of gold and to speculate on the possible continuity of this prospective rock package into neighbouring regions.