The Engineer Mine, British Columbia: An example of epithermal Au-Ag mineralization with mixed alkaline and subalkaline characteristics
The Engineer Mine epithermal precious metal deposit in British Columbia, Canada, is related to Eocene Sloko-Skukum-Group (SSG) volcanism and, according to previous studies, contains roscoelite in intimate association with electrum. Roscoelite, a vanadian mica, is considered characteristic of low-sul...
| Main Authors: | , , , , , , |
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| Format: | Journal Article |
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Elsevier Science BV
2017
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| Online Access: | http://hdl.handle.net/20.500.11937/53095 |
| _version_ | 1848759064362745856 |
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| author | Millonig, L. Beinlich, Andreas Raudsepp, M. Devine, F. Archibald, D. Linnen, R. Groat, L. |
| author_facet | Millonig, L. Beinlich, Andreas Raudsepp, M. Devine, F. Archibald, D. Linnen, R. Groat, L. |
| author_sort | Millonig, L. |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | The Engineer Mine epithermal precious metal deposit in British Columbia, Canada, is related to Eocene Sloko-Skukum-Group (SSG) volcanism and, according to previous studies, contains roscoelite in intimate association with electrum. Roscoelite, a vanadian mica, is considered characteristic of low-sulfidation epithermal deposits related to alkaline magmatism. This contradicts the fact that the SSG volcanics are subalkaline. In order to address this ambiguity and to accurately classify the style of epithermal mineralization at the Engineer Mine we conducted detailed petrographic, mineralogical, geochronological, fluid inclusion, and stable isotope studies. The principal ore assemblage of the Engineer Mine epithermal veins precipitated in response to boiling during a hydrothermal event at 49.90 Ma ± 0.25 Ma. During this event electrum, arsenopyrite, pyrite ± chalcopyrite ± sphalerite ± löllingite ± tetrahedrite-group phases ± allargentum ± acanthite ± hessite ± dyscrasite ± stibarsen ± galena and an unidentified Ag-rich phase were deposited in conjunction with amorphous silica, platy and rhombic calcite, K-feldspar, and vanadian illite. Fluid inclusion and stable isotope data suggest that the ore-forming fluid was boiling at ~220 °C during vein mineralization and had an isotopic composition derived from local meteoric water. Based on these results the Engineer Mine is classified as an epithermal low-sulfidation deposit, which shares similarities with alkaline and subalkaline epithermal low-sulfidation deposits. This is attributed to the fact that the SSG volcanic rocks are borderline subalkaline to alkaline in character and that the sedimentary host rocks are vanadium-bearing. These sedimentary rocks contributed the bulk of the vanadium to the Engineer Mine epithermal system. The presence of roscoelite at the Engineer Mine could not be confirmed during this study. The mica referred to as roscoelite in previous publications instead is vanadian illite. To our knowledge the only alkaline low-sulfidation epithermal precious metal deposit that contains V-mica which exclusively qualifies as true roscoelite is the Porgera deposit, Papua New Guinea. |
| first_indexed | 2025-11-14T09:53:56Z |
| format | Journal Article |
| id | curtin-20.500.11937-53095 |
| institution | Curtin University Malaysia |
| institution_category | Local University |
| last_indexed | 2025-11-14T09:53:56Z |
| publishDate | 2017 |
| publisher | Elsevier Science BV |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | curtin-20.500.11937-530952017-10-09T06:04:42Z The Engineer Mine, British Columbia: An example of epithermal Au-Ag mineralization with mixed alkaline and subalkaline characteristics Millonig, L. Beinlich, Andreas Raudsepp, M. Devine, F. Archibald, D. Linnen, R. Groat, L. The Engineer Mine epithermal precious metal deposit in British Columbia, Canada, is related to Eocene Sloko-Skukum-Group (SSG) volcanism and, according to previous studies, contains roscoelite in intimate association with electrum. Roscoelite, a vanadian mica, is considered characteristic of low-sulfidation epithermal deposits related to alkaline magmatism. This contradicts the fact that the SSG volcanics are subalkaline. In order to address this ambiguity and to accurately classify the style of epithermal mineralization at the Engineer Mine we conducted detailed petrographic, mineralogical, geochronological, fluid inclusion, and stable isotope studies. The principal ore assemblage of the Engineer Mine epithermal veins precipitated in response to boiling during a hydrothermal event at 49.90 Ma ± 0.25 Ma. During this event electrum, arsenopyrite, pyrite ± chalcopyrite ± sphalerite ± löllingite ± tetrahedrite-group phases ± allargentum ± acanthite ± hessite ± dyscrasite ± stibarsen ± galena and an unidentified Ag-rich phase were deposited in conjunction with amorphous silica, platy and rhombic calcite, K-feldspar, and vanadian illite. Fluid inclusion and stable isotope data suggest that the ore-forming fluid was boiling at ~220 °C during vein mineralization and had an isotopic composition derived from local meteoric water. Based on these results the Engineer Mine is classified as an epithermal low-sulfidation deposit, which shares similarities with alkaline and subalkaline epithermal low-sulfidation deposits. This is attributed to the fact that the SSG volcanic rocks are borderline subalkaline to alkaline in character and that the sedimentary host rocks are vanadium-bearing. These sedimentary rocks contributed the bulk of the vanadium to the Engineer Mine epithermal system. The presence of roscoelite at the Engineer Mine could not be confirmed during this study. The mica referred to as roscoelite in previous publications instead is vanadian illite. To our knowledge the only alkaline low-sulfidation epithermal precious metal deposit that contains V-mica which exclusively qualifies as true roscoelite is the Porgera deposit, Papua New Guinea. 2017 Journal Article http://hdl.handle.net/20.500.11937/53095 10.1016/j.oregeorev.2016.12.023 Elsevier Science BV restricted |
| spellingShingle | Millonig, L. Beinlich, Andreas Raudsepp, M. Devine, F. Archibald, D. Linnen, R. Groat, L. The Engineer Mine, British Columbia: An example of epithermal Au-Ag mineralization with mixed alkaline and subalkaline characteristics |
| title | The Engineer Mine, British Columbia: An example of epithermal Au-Ag mineralization with mixed alkaline and subalkaline characteristics |
| title_full | The Engineer Mine, British Columbia: An example of epithermal Au-Ag mineralization with mixed alkaline and subalkaline characteristics |
| title_fullStr | The Engineer Mine, British Columbia: An example of epithermal Au-Ag mineralization with mixed alkaline and subalkaline characteristics |
| title_full_unstemmed | The Engineer Mine, British Columbia: An example of epithermal Au-Ag mineralization with mixed alkaline and subalkaline characteristics |
| title_short | The Engineer Mine, British Columbia: An example of epithermal Au-Ag mineralization with mixed alkaline and subalkaline characteristics |
| title_sort | engineer mine, british columbia: an example of epithermal au-ag mineralization with mixed alkaline and subalkaline characteristics |
| url | http://hdl.handle.net/20.500.11937/53095 |