| Title | Paleoredox conditions, hydrothermal history, and target vectoring in the MacMillan Pass base-metal district, Yukon, Canada: 1 - lithogeochemistry of proximal and distal shales |
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| Author | Leighton, C; Leybourne, M I; Layton-Matthews, D; Peter, J M ; Gadd, G M; Voinot, A |
| Source | Canadian Mineralogist vol. 59, no. 5, 2021 p. 1207-1232, https://doi.org/10.3749/canmin.2000075 |
| Image |  |
| Year | 2021 |
| Alt Series | Natural Resources Canada, Contribution Series 20200586 |
| Publisher | Mineralogical Association of Canada |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| Related | This publication is related to Paleoredox conditions,
hydrothermal history, and target vectoring in the MacMillan Pass base-metal district, Yukon, Canada: 2 - pyrite paragenesis and mineral chemistry |
| File format | pdf; html |
| Province | Yukon |
| NTS | 105I; 105J; 105K; 105N; 105O; 105P |
| Area | MacMillan Pass |
| Lat/Long WENS | -134.0000 -128.0000 64.0000 62.0000 |
| Subjects | economic geology; geochemistry; tectonics; Science and Technology; Nature and Environment; mineral exploration; mineral potential; mineral deposits; base metals; zinc; lead; silver; barium; uranium;
molybdenum; ore mineral genesis; mineralization; lithogeochemistry; bedrock geology; lithology; sedimentary rocks; clasts; shales; tectonic history; hydrothermal systems; fluid flow; fluid dynamics; host rocks; geochemical anomalies; thermal
analyses; mineral enrichment; organic carbon; isotopic studies; isotopes; sulphur; strontium; barite; remobilization; precipitation; MacMillan Pass District; Earn Group; Tom Deposit; Jason Deposit; Phanerozoic; Paleozoic; Devonian |
| Illustrations | location maps; geoscientific sketch maps; photographs; tables; profiles; plots; ternary diagrams |
| Program | Targeted Geoscience Initiative (TGI-5) Volcanic and sedimentary systems - sedimentary exhalative ore systems |
| Released | 2021 10 07 |
| Abstract | The MacMillan Pass District in Yukon, Canada, hosts the Tom and Jason clastic sediment-hosted Zn-Pb-Ag-(Ba) deposits. Bulk geochemical paleoredox proxies (Eu/Eu*, Ce/Ce*, Mo, Re/Mo, and Ni/Co) indicate
anoxic-dysoxic water column and sulfidic porewater conditions persisted during the Late Devonian deposition of the Lower Earn Group host rocks. Positive Eu/Eu* anomalies (up to 3.31) in sulfide mineralization at the Tom deposit are consistent with
relatively high temperature (probably >250 °C), reducing, acidic hydrothermal fluids that infiltrated laterally through unconsolidated sediments proximal to the hydrothermal upflow zone and/or exhaled at the seafloor as moderate- to high-density
brines. Molybdenum and U enrichment factors (relative to upper continental crust) and Mo/organic C values are consistent with a moderately restricted basin; Mo/C values fall between those of the Black Sea (highly restricted) and the Framvaren Inlet
(moderately restricted). A Ba-rich shale was identified in rocks that are distal and time-equivalent units to the Pb-Zn mineralization; based on the bulk chemical compositions and on previous S and Sr isotope studies, we interpret the baryte in this
unit to be largely hydrothermal in origin and perhaps remobilized and reprecipitated during hydrothermal base-metal mineralization. |
| Summary | (Plain Language Summary, not published)
This contribution focuses on one of Canada's premiere lead-zinc mineralized districts in Yukon. The impetus for this work was to decipher the mechanisms
of deposit formation and development of methods and methodologies that can be used to explore for additional deposits in the district, and elsewhere. Whole-rock geochemical analyses of the immediate host rocks (above and below mineralization) both
within the deposit and further away were used to determine the conditions of the mineralizing fluid (hot, reducing, acidic), the water column (nil to little free oxygen), and the immediate subsurface muds (sulfidic). Certain geochemical parameters
indicate that the deposits formed in a moderately restricted basin. Barium in the host rocks is interpreted to have originated from the mineralizing fluid. Similar analyses of other areas can be used to make inferences about the mechanisms of
emplacement of mineralization, and the setting under which these occurred. |
| GEOSCAN ID | 327840 |
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