| Titre | The mineralogical evolution of the clastic dominant-type zn-pb ± ba deposits at macmillan pass (Yukon, Canada)-tracing subseafloor barite replacement in the layered mineralization |
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| Auteur | Magnall, J M; Gleeson, S A; Creaser, R A; Paradis, S; Glodny, J; Richard Kyle, J |
| Source | Economic Geology vol. 115, issue 5, 2020 p. 961-979, https://doi.org/10.5382/econgeo.4730 |
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| Année | 2020 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20200683 |
| Éditeur | Society of Economic Geologists |
| Document | publication en série |
| Lang. | anglais |
| DOI | https://doi.org/10.5382/econgeo.4730 |
| Media | papier; en ligne; numérique |
| Formats | pdf; html |
| Province | Yukon |
| Lat/Long OENS | -142.0000 -121.0000 65.0000 55.0000 |
| Sujets | barytine; feldspath; kaolinite; Bassin de Selwyn ; minéraux métalliques; Sciences et technologie; sédimentologie |
| Illustrations | cartes de localisation; coupes transversales; échelles stratigraphiques; diagrammes; photographies; tableaux; représentations graphiques combinées |
| Diffusé | 2020 08 01 |
| Résumé | (disponible en anglais seulement)
Clastic dominant-type massive sulfide deposits are well preserved in Upper Devonian carbonaceous mudstones in the Macmillan Pass district (Yukon, Canada). The
Macmillan Pass deposits have been considered to be type examples of sedimentary exhalative Zn-Pb mineralization, whereby sulfides precipitated when hydrothermal fluids were vented into a euxinic (H2S-bearing) water column. We propose a new
mineralization model, documenting the mineralogical evolution of layered mineralization. We show that textures previously interpreted to form via depositional processes actually formed by subseafloor replacement of diagenetic barite. Mineral
assemblages associated with barite dissolution in the layered mineralization include (1) barium carbonate phases (witherite, barytocalcite, and norsethite), which are intergrown with Zn-Pb sulfides and represent localized Ba mass transfer, and (2)
barium feldspar (celsian, hyalophane) that is abundant in the mudstones surrounding the layered mineralization. The barium feldspar formed following transport of Ba in low-sulfate fluids on the margins of the subseafloor replacement system. This
resulted in whole-rock Ba enrichments (up to 5 wt %) in mudstones 15 m below and above the layered mineralization. High Ba in these surrounding mudstones is coupled with decreasing K/Al ratios, indicative of secondary illite and kaolinite. The
source(s) of fluids related to the diagenetic (barite, barytocalcite) and hydrothermal (ankerite) assemblages can be constrained using Sr isotopes. Whereas highly radiogenic 87Sr/86Sr values (>0.714) in ankerite correspond with host-rock alteration
within the vent complex, the overlying barite and barytocalcite preserve lower 87Sr/86Sr values (<0.714), providing evidence of mixing between a radiogenic fluid (likely a formation water) and Late Devonian seawater. The complex mineralogy and
paragenesis contained within the layered mineralization are linked to a protracted history of diagenetic and hydrothermal fluid events, all of which took place in and peripheral to a subseafloor replacement hydrothermal system. |
| GEOSCAN ID | 327971 |
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