| Title | Are there elephants hiding in the Jurassic of Yukon? A tectonomagmatic perspective on porphyry prospectivity |
| Download | Download (whole publication) |
| 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 |
| Year | 2015 |
| Publisher | Natural Resources Canada |
| Document | open file |
| Lang. | English |
| Media | on-line; digital |
| Related | This publication is contained in Rogers, N; (2015). TGI 4 -
Intrusion Related Mineralisation Project: new vectors to buried porphyry-style mineralisation, Geological Survey of Canada, Open File 7843 |
| 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 |
| Viewing | |
| Natural Resources Canada Library - Ottawa (Earth Sciences) |
| |
| Program | Intrusion/Porphyry Ore Systems, Targeted Geoscience Initiative (TGI-4) |
| Links | Canadian Database of Geochemical Surveys, downloadable
files
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| Links | Banque de données de levés géochimiques du Canada,
fichiers téléchargeables
|
| Released | 2015 06 11 |
| 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. |
| GEOSCAN ID | 296485 |
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