| Title | Are there elephants hiding in the Jurassic of Yukon? A tectonomagmatic perspective on porphyry prospectivity |
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| Licence | Please note the adoption of the Open Government Licence - Canada
supersedes any previous licences. |
| Author | Chapman, J B |
| Source | TGI 4 - Intrusion Related Mineralisation Project: new vectors to buried porphyry-style mineralisation; by Rogers, N (ed.); Geological Survey of Canada, Open File 7843, 2015 p. 493-506, https://doi.org/10.4095/296485  Open Access |
| Links | Canadian Database of Geochemical Surveys, downloadable
files
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| Links | Banque de données de levés géochimiques du Canada,
fichiers téléchargeables
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| Image |  |
| Year | 2015 |
| Publisher | Natural Resources Canada |
| Document | open file |
| Lang. | English |
| Media | on-line; digital |
| Related | This publication is contained in TGI 4 - Intrusion Related
Mineralisation Project: new vectors to buried porphyry-style mineralisation |
| File format | pdf |
| Province | Yukon |
| NTS | 105D; 105E; 105L; 115A; 115H; 115I |
| Area | Whitehorse; Carmacks |
| Lat/Long WENS | -138.0000 -134.5000 63.0000 60.5000 |
| Subjects | economic geology; tectonics; porphyry deposits; porphyry copper; mineral exploration; mineralization; tungsten; molybdenum; copper; gold; tectonic environments; tectonic setting; magmatic deposits;
magmatic rocks; Sisson deposit; Nashwaak Granite; Mesozoic; Jurassic |
| Illustrations | location maps; photographs; plots; ternary diagrams |
| Program | Targeted Geoscience Initiative (TGI-4) Intrusion/Porphyry Ore Systems |
| Released | 2015 06 11; 2023 03 17 |
| Abstract | Within British Columbia, Triassic-Jurassic felsic plutonic and intrusive rocks of the Stikinia and Quesnellia terranes are very much considered “elephant country”, and are spatially and genetically
associated with some of the most significant porphyry Cu-Mo deposits in North America. However, where these terranes meet and merge in central Yukon, little significant mineralization has been discovered in similarly aged felsic plutonic rocks and
they host only one operating Cu mine, despite outcrop covering hundreds of square kilometres. The reasons for this discrepancy are not clear. In order to provide assessment of the tectonomagmatic setting and porphyry prospectivity of Jurassic
plutonic rocks within Yukon, 65 unmineralized samples from across the district have been analyzed for their whole rock major and trace element geochemistry, and their zircon Ce4+/Ce3+ ratios were determined by laser ablation ICP-MS. Most samples plot
within calc-alkaline to high K calc-alkaline fields within a plot of SiO2 vs. K2O, although data display significant scatter and lack any strong trend, suggestive of later disturbance of the K content. Rocks from all sampling locations show HFSE
depletions and negative Nb anomalies characteristic of suprasubduction zone environments, and commonly depleted HREE patterns are suggestive of melt generated below the depth of garnet stability. Plots of Sr/Y vs. Y and La/YbN vs. YbN both indicate
significant adakite-like and adakitic characteristics in a subset of the samples analysed. Taken together, the suprasubduction zone character and presence of adakite-like magmatism have been suggested as strong indicators of high porphyry potential
in other parts of the world. Zircon Ce4+/Ce3+ values were highly variable and ranged up to more than 2100, an order of magnitude greater than previous studies have suggested as a porphyry prospectivity threshold. However, aluminum-inhornblende data
and Cu and Mo contents well below crustal abundances suggest that Jurassic plutonic rocks may represent the mid-crustal, volatile-depleted residue of porphyry-related magmatism that has been eroded away. Future exploration for Cu-Mo-Au mineralization
within Yukon will depend on understanding of tectonic uplift across the region, and better constraint on the genesis of known mineralization. |
| Summary | (Plain Language Summary, not published)
The Targeted Geoscience Initiative (TGI-4) is a collaborative federal geoscience program that provides industry with the next generation of geoscience
knowledge and innovative techniques to better detect buried mineral deposits, thereby reducing some of the risks of exploration. This volume summarises research activities completed under the TGI 4 Intrusion Related Mineralisation Project that
focused on porphyry-style ore systems related to the Cu- and Cu-Mo deposits of South-Central British Columbia and the Sn-W-Mo-In deposits in New Brunswick, Nova Scotia and Newfoundland. |
| GEOSCAN ID | 296485 |
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