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TitleLatest Targeted Geoscience Initiative research results on sediment-hosted base metal sulfide deposits
AuthorGadd, M GORCID logo; Peter, J MORCID logo
SourceAME Roundup 2019, technical sessions abstract guide; 2019 p. 10
Alt SeriesNatural Resources Canada, Contribution Series 20200540
MeetingAME Roundup 2019; Vancouver, BC; CA; January 28-31, 2019
Mediaon-line; digital
File formatpdf
NTS106E; 106F; 106K; 106L; 116H; 116I
AreaPeel River; Nick River
Lat/Long WENS-138.0000 -133.0000 67.0000 65.5000
Subjectseconomic geology; geochemistry; Science and Technology; Nature and Environment; ore mineral genesis; ore controls; mineral deposits; base metals; sedimentary ore deposits; sulphide deposits; volcano-sedimentary ore deposits; nickel; molybdenum; zinc; gold; lead; silver; barium; host rocks; sedimentary rocks; shales; volcano-sedimentary strata; paleoenvironment; isotopic studies; mass spectrometer analysis; platinum group elements
ProgramTargeted Geoscience Initiative (TGI-5)
Released2019 01 01
AbstractThe authors present results from TGI research on hyperenriched black shale (HEBS) Ni-Mo-Zn-PGE-Au-Re deposits and sedimentary exhalative (SEDEX) Zn-Pb-(Ag-Ba) deposits.
North Yukon is host to several occurrences of HEBS Ni-Mo-Zn-PGE-Au mineralization, including Nick and Peel River. The redox conditions of marine water columns and sediments are thought to be a primary controlling factor in HEBS formation. To evaluate the ambient paleoenvironmental conditions, several robust lithogeochemical proxies have been applied to HEBS mineralization and host rocks. Additionally, traditional (sulphur) and non-traditional (molybdenum and thallium) stable isotopes have been measured in host rocks and mineralization to provide insights into metal and sulphur sources. Collectively, the data reveal that water column conditions during background sedimentation were suboxic. The HEBS sulphide mineralization, however, was precipitated in anoxic to euxinic conditions at or close to the seafloor in the sub-surface. The molybdenum and thallium isotopic values of the Peel River sedimentary rocks and HEBS mineralization, together with the other bulk paleoredox indicators and REE, indicate that the molybdenum and thallium were both sourced from seawater. Highly negative sulphur isotope compositions show that biogenically reduced seawater sulphate was the ultimate source of reduced sulphur in the mineralization. Laser ablation-ICP-MS reveals that pyrite within HEBS is the predominant mineral host for precious metals (palladium, platinum, gold, rhenium). Precious metals are absent in late-stage pyrite-marcasite veins, which effectively constrains the relative age of mineralization to diagenesis.
Research on SEDEX deposits has focused on pyrite chemistry in the MacMillan Pass zinc-lead-silver-barium district. Four pyrite generations are identified in mineralized and distal, age-equivalent, unmineralized rocks: syn-sedimentary (Py1), diagenetic (Py2), hydrothermal (Py3), and metamorphic (Py4). Significantly, a SEDEX mineralized element suite (Co-As-Ag-Bi-Tl-Pb-Zn) is recognized within Py3 in the distal (2-4 km), unmineralized samples. This recognition suggests that pyrite chemistry in MacMillan Pass may be useful in vectoring toward concealed mineralization.

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