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TitleAre there elephants hiding in the Jurassic of Yukon? A tectonomagmatic perspective on porphyry prospectivity
LicencePlease note the adoption of the Open Government Licence - Canada supersedes any previous licences.
AuthorChapman, J BORCID logo
SourceTGI 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, Open Access logo Open Access
LinksCanadian Database of Geochemical Surveys, downloadable files
LinksBanque de données de levés géochimiques du Canada, fichiers téléchargeables
PublisherNatural Resources Canada
Documentopen file
Mediaon-line; digital
RelatedThis publication is contained in TGI 4 - Intrusion Related Mineralisation Project: new vectors to buried porphyry-style mineralisation
File formatpdf
NTS105D; 105E; 105L; 115A; 115H; 115I
AreaWhitehorse; Carmacks
Lat/Long WENS-138.0000 -134.5000 63.0000 60.5000
Subjectseconomic 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
Illustrationslocation maps; photographs; plots; ternary diagrams
ProgramTargeted Geoscience Initiative (TGI-4) Intrusion/Porphyry Ore Systems
Released2015 06 11; 2023 03 17
AbstractWithin 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.

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