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TitleBase metal metallogeny of the Selwyn Basin, Canada
AuthorGoodfellow, W D
SourceMineral deposits of Canada: a synthesis of major deposit-types, district metallogeny, the evolution of geological provinces, and exploration methods; by Goodfellow, W D (ed.); Geological Association of Canada, Mineral Deposits Division, Special Publication no. 5, 2007 p. 553-579
Year2007
Alt SeriesEarth Sciences Sector, Contribution Series 20070206
PublisherGeological Association of Canada, Mineral Deposits Division (St. John's, NL, Canada)
Documentserial
Lang.English
Mediapaper; DVD; digital
RelatedThis publication is contained in Goodfellow, W D; (2007). Mineral deposits of Canada: a synthesis of major deposit-types, district metallogeny, the evolution of geological provinces, and exploration methods, Geological Association of Canada, Mineral Deposits Division, Special Publication no. 5
File formatpdf
ProvinceBritish Columbia; Northwest Territories; Yukon
NTS94B; 94C; 94E; 94F; 94K; 94L; 94M; 95B; 95C; 95D; 95E; 95F; 95K; 95L; 95M; 104I; 104P; 105A; 105B; 105G; 105H; 105I; 105J; 105K; 105M; 105N; 105O; 105P; 106A; 106B; 106C; 106D; 116A
AreaSelwyn Basin; MacMillan Pass; Gataga; Howards Pass; Anvil
Lat/Long WENS-138.0000 -123.0000 65.0000 56.0000
Subjectseconomic geology; metallic minerals; geochemistry; mineral occurrences; mineral deposits; mineralization; base metals; metallogeny; zinc; lead; silver; copper; gold; sedimentary ore deposits; sedimentary basins; hydrothermal deposits; tectonic setting; hydrothermal alteration; alteration; lithogeochemistry; Clear Lake Deposit; Mel Deposit; Windermere Supergroup; sedimentary exhalative deposits; Cambrian; Silurian; Devonian; Paleozoic
Illustrationssketch maps; photographs; photomicrographs; stratigraphic sections
ProgramConsolidating Canada's Geoscience Knowledge
ProgramTargeted Geoscience Initiative (TGI-3), 2005-2010
AbstractThe sedimentary exhalative (SEDEX) deposits of the Selwyn Basin occur in four major districts: MacMillan Pass and Gataga (Late Devonian), Howards Pass (Early Silurian), and Anvil (Late Cambrian). In addition, there are the Clear Lake (Late Devonian) and Mel (Cambrian) deposits that do not fall inside the districts above. There are twelve major SEDEX deposits with proven reserves that include past producers Faro, Vangorda, and Grum. The deposits range in size from the giant Howards Pass deposit at 115 Mt to the relatively small Driftpile deposit at 2.4 Mt. Metal grades and ratios are highly variable between deposits, with values ranging from 4.7 to 16.2% Zn, 2.0 to 5.5% Pb, and up to 110 g/t Ag. The average Cu and Au contents are generally very low except for the Vangorda and DY deposits in the Anvil District where values range up to 0.3% and 0.8 g/t, respectively. Stratiform barite deposits also occur in the basin.

The Selwyn Basin is an elongate rift-controlled, epicratonic sedimentary basin, extending from Alaska through the Yukon, western Northwest Territories, and British Columbia, which is flanked to the east and north by carbonate platforms that host co-genetic Mississippi Valley-type deposits. The sedimentary architecture of this continental rift consists of a Late Proterozoic thick synrift, mostly oxidized, clastic sequence (Windermere Supergroup), which is overlain by Paleozoic sag or postrift basinal, reduced facies shales and cherts that host the SEDEX deposits.

SEDEX deposits were formed by the reaction of metals in basinal saline fluids with biogenic H2S in the ambient anoxic water column. Based on available fluid inclusion data, the morphology of stratiform sulphide bodies, and vent textures, hydrothermal fluids that vented into seawater behaved either as buoyant plumes or bottom-hugging brines. SEDEX deposits formed from buoyant plumes are mound-shaped and characterized by rapid thickness changes away from the vent. Because deposits formed from dense brines commonly occupy depressions remote from vent sites, they tend to be more uniform in thickness, laterally widespread, delicately bedded, and not strongly zoned.
GEOSCAN ID224195