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TitleLithogeochemical and sulfur isotope indicators of environment of formation and genesis of the Moss hyper-enriched black shale showing, Yukon
AuthorGadd, M GORCID logo; Peter, J MORCID logo
SourceGoldschmidt abstracts, 2019; 1061, 2019 p. 1 Open Access logo Open Access
LinksOnline - En ligne
Alt SeriesNatural Resources Canada, Contribution Series 20200416
PublisherEuropean Association of Geochemistry
PublisherGeochemical Society
MeetingGoldschmidt2019 Conference; Barcelona; ES; August 18-23, 2019
DocumentWeb site
Mediaon-line; digital
File formatpdf
NTS106E/09; 106E/10; 106E/11; 106E/12; 106E/13; 106E/14; 106E/15; 106E/16; 106F/11; 106F/12; 106F/13; 106F/14; 106K/03; 106K/04; 106K/05; 106K/06; 106K/11; 106K/12; 106K/13; 106K/14; 106L; 116H/09; 116H/10; 116H/11; 116H/12; 116H/13; 116H/14; 116H/15; 116H/16; 116I
AreaRichardson Mountains
Lat/Long WENS-138.0000 -133.0000 67.0000 65.5000
Subjectseconomic geology; geochemistry; stratigraphy; mineral deposits; nickel; molybdenum; zinc; platinum; palladium; gold; iron; sulphides; sedimentary ore deposits; strata-bound deposits; mineral exploration; mineral potential; ore mineral genesis; mineralization; ore controls; lithogeochemistry; isotopic studies; stable isotope studies; sulphur isotope ratios; sulphur geochemistry; sedimentary basins; bedrock geology; lithology; sedimentary rocks; black shales; cherts; shales; silts; structural features; faults; paleoenvironment; sedimentary environments; marine environments; sea water geochemistry; depositional environment; sedimentation; clastics; precipitation; whole rock analyses; geochemical analyses; bulk composition; spectrometric analyses; organic geochemistry; organic carbon analyses; paleogeography; Richardson Trough; Moss showing; Yukon Stable Block; Imperial Formation; Canol Formation; Road River Group; platinum group elements; Phanerozoic; Paleozoic; Devonian
ProgramTargeted Geoscience Initiative (TGI-5) Volcanic and sedimentary systems - volcanogenic massive sulphide ore systems
Released2019 08 01
AbstractThe Moss Ni-Mo-Zn-Pt-Pd-Re-Au hyper-enriched black shale (HEBS) showing is located the western Richardson Mountains and is one of several in northern Yukon. The mineralization consists of a thin (1-3 cm), stratiform, semi-massive sulfide horizon that occurs at the stratigraphic contact between the Road River Group and Canol Formation. We evaluate the ambient paleoenvironmental conditions using several robust lithogeochemical proxies. Prior to HEBS formation, clastic sedimentation predominated, whereas chemical sedimentation prevailed during and immediately after HEBS formation. Rare earth element-Y data indicate that the water column was (weakly) oxygenated (Ce/Ce*SN <1), that there was no hydrothermal venting (Eu/Eu*SN approx. Equal to 1), and that there was a significant seawater influence on the sedimentary environment (Y/Ho > 28) for the entire deposition interval. High (>10) authigenic Mo/U ratios indicate that seawater-sourced ferromanganese oxyhydroxide particles precipitated in the water column and were shuttled to (and sedimented on) the seafloor. The particles dissolved within the reducing, organic matter-rich sediments and precipitated as sulfides. Negative G34S values (-19.3 to -23 per mille) of the HEBS sulfides indicate that the sulfur originated by microbial reduction of seawater sulfate. Collectively, these data signify a basinal environment that experienced varying degrees of restriction and stratification, but fresh (i.e., unfractionated) marine waters delivered metals, metalloids, and sulfur [1]. Such a geological setting is considered critical for the formation and preservation of HEBS mineralization. [1] Gadd et al. 2019, Geological Survey of Canada Open File 8549, p. 163-178.
Summary(Plain Language Summary, not published)
This abstract summarizes recent TGI-related research on the formation of metal-rich shales in northern Yukon. The Moss showing is one of several deposits in Yukon are exceptionally rich in a variety of metals (Ni-Pt-Pd-Au-Re-Mo), but the mineralization is geographically widespread. This work explores in detail numerous geochemical signals recorded in the rocks, and contributes to the salient goal of developing an internally consistent hypothesis for how these deposits form.

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