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GEOREF RECORD

Evidence for microbially mediated silver enrichment in a Middle Cambrian Burgess Shale-type deposit, Mackenzie Mountains, northwestern Canada

Julien Kimmig and Brian R. Pratt
Evidence for microbially mediated silver enrichment in a Middle Cambrian Burgess Shale-type deposit, Mackenzie Mountains, northwestern Canada
Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre (February 2022) 59 (2): 123-133

Abstract

The Selwyn basin and Mackenzie platform of northwestern Canada house an array of mineral deposits and prospects that are rich in silver, including Neoproterozoic red-bed or Kupferschiefer-type Cu and lower Paleozoic sedimentary exhalative (SEDEX) and Zn-Pb deposits. Within this overall metallogenic setting, the middle Cambrian (Drumian) Rockslide Formation was deposited under a largely oxic water column on the platform-to-basin slope along the eastern side of the Selwyn basin. The formation includes an interval termed the Ravens Throat River Lagerstaette, which is a localized Burgess Shale-type calcareous mudstone about 2 m thick that preserves soft-bodied fossils. The mudstone contains comparatively large amounts of organic carbon preserved as thin carbonaceous laminae and discontinuous seams, representing benthic microbial mats, the remains of cyanobacteria and algae that were living in the water column, fecal pellets, large coprolites, and degraded animal tissues. The upper part of the Rockslide Formation, including the fossiliferous interval, contains elevated concentrations of Ag, up to 0.47 ppm. Some of the Ag in the mudstone occurs as aggregates of elemental particles approximately 10 mu m in size, preferentially on the carbonaceous material comprising the coprolites. This localized enrichment suggests bioaccumulation of Ag nanoparticles or Ag (super +) from the water column by microorganisms on the coprolites or degrading organic matter in them. The source of the Ag may have been from penecontemporaneous SEDEX metallogeny or from broadly related subsurface fluids in the Selwyn Basin that enriched the overlying seawater.


ISSN: 0008-4077
EISSN: 1480-3313
Coden: CJESAP
Serial Title: Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre
Serial Volume: 59
Serial Issue: 2
Title: Evidence for microbially mediated silver enrichment in a Middle Cambrian Burgess Shale-type deposit, Mackenzie Mountains, northwestern Canada
Affiliation: Pennsylvania State University, Department of Geosciences, University Park, PA, United States
Pages: 123-133
Published: 202202
Text Language: English
Summary Language: French
Publisher: National Research Council of Canada, Ottawa, ON, Canada
References: 100
Accession Number: 2022-012923
Categories: Geochemistry of rocks, soils, and sedimentsEconomic geology, geology of ore deposits
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. geol. sketch map, 2 tables, strat. col.
Secondary Affiliation: University of Saskatchewan, Department of Geological Sciences, Saskatoon, SK, CAN, Canada
Country of Publication: Canada
Secondary Affiliation: GeoRef, Copyright 2022, American Geosciences Institute. Reference includes data from Canadian Science Publishing, NRC Research Press, Ottawa, ON, Canada. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 2022
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