| Title | Superimposed Late Cretaceous and earliest Eocene gold mineralization and deformation events along the
Llewellyn-Tally Ho deformation corridor in northwest British Columbia and southern Yukon |
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| Licence | Please note the adoption of the Open Government Licence - Canada
supersedes any previous licences. |
| Author | Castonguay, S ;
Ootes, L; Devine, F; Friedman, R |
| Source | Targeted Geoscience Initiative 5: contributions to the understanding of Canadian gold systems; by Mercier-Langevin, P (ed.); Lawley, C J M (ed.); Castonguay, S (ed.); Geological Survey of Canada, Open File 8712, 2020 p. 223-236, https://doi.org/10.4095/326039  Open Access |
| Image |  |
| Year | 2020 |
| Publisher | Natural Resources Canada |
| Document | open file |
| Lang. | English |
| Media | on-line; digital |
| Related | This publication is contained in Targeted Geoscience
Initiative 5: contributions to the understanding of Canadian gold systems |
| Related | This publication is related to Superimposed auriferous
structural events along the Llewellyn-Tally Ho deformation corridor in southern Yukon and northwest British Columbia |
| File format | pdf |
| Province | British Columbia; Yukon |
| NTS | 104M/07; 104M/08; 104M/09; 104M/10; 104M/11; 104M/12; 104M/13; 104M/14; 104M/15; 104M/16; 105D/01; 105D/02; 105D/03; 105D/04; 105D/05; 105D/06; 105D/07; 105D/08 |
| Area | Carcross; Fraser; Engineer; Wann River; Taglish lake; Racine Lake; Moon Lake; Tutshi Lake; Bennett Lake; Wheaton River; Mount Hodnett; Tally-Ho Mountain; Annie Lake |
| Lat/Long WENS | -135.5833 -134.0000 60.3667 59.2500 |
| Subjects | economic geology; tectonics; structural geology; geochronology; Science and Technology; Nature and Environment; Paleogene; Eocene; Upper Cretaceous; mineral deposits; gold; epithermal deposits;
mesothermal deposits; skarn deposits; vein deposits; mineral exploration; exploration guidelines; ore mineral genesis; mineralization; ore controls; structural controls; metallogeny; tectonic history; metamorphism; deformation; foliation; mylonites;
lineations; strain; faulting; magmatism; intrusions; plutons; dykes; hydrothermal alteration; host rocks; bedrock geology; structural features; fault zones; faults; faults, strike-slip; splays; shear zones; fractures; lithology; igneous rocks;
intrusive rocks; granodiorites; porphyries; monzonites; granites; monzodiorites; mafic intrusive rocks; ultramafic rocks; volcanic rocks; rhyolites; andesites; tuffs; lava flows; basalts; sedimentary rocks; argillites; greywackes; metamorphic rocks;
amphibolites; metasedimentary rocks; marbles; skarns; breccias; radiometric dating; uranium lead dating; zircon dates; mineral occurrences; fabric analyses; field relations; Canadian Cordillera; Intermontane Belt; Coastal Belt; Nisling Terrane;
Yukon-Tanana Terrane; Tally-Ho Shear Zone; Engineer Mine; Llewellyn Fault; Stikine Terrane; Stuhini Group; Juneau Gold Camp; Sloko Group; Windy Table Coplex; Carmacks Group; Laberge Group; Boundary Ranges Metamorphic Suite; Whitehorse Suite; Casino
Suite; Bennett Granite; Lewes River Group; Povoas Formation; Skarn Zone Prospect; Tannis Prospect; Engineer Mountain Volcanic Complex; Mount Skukum Mine; Big Creek Fault Zone; Dawson Range Polymetallic Belt; Phanerozoic; Cenozoic; Tertiary; Mesozoic;
Cretaceous; Jurassic; Triassic; Paleozoic; Permian; Carboniferous; Devonian |
| Illustrations | location maps; geoscientific sketch maps; photographs; cross-sections; tables; geochronological charts |
| Program | Targeted Geoscience Initiative (TGI-5) Gold ore systems |
| Released | 2020 06 11; 2023 03 17 |
| Abstract | A revised geological and metallogenic framework for the Llewellyn-Tally Ho deformation corridor in southern Yukon and northwest British Columbia is proposed. The long-lived fault zone generally
demarcates the eastern and western limits of the Nisling (Yukon-Tanana) and Stikine terrane, respectively. Epithermal (e.g. Engineer mine), intrusion-related and 'mesothermal' (e.g. Bennett plateau - Middle Ridge areas and part of the Wheaton
district and Wann River area) gold deposits and occurrences are spatially associated with the Llewellyn-Tally Ho deformation corridor.
The Llewellyn fault is a southeast-striking, steeply dipping, brittle and dextral strike-slip structure that
overprints penetrative fabrics and ductile deformation. The Tally Ho shear zone, Yukon, represents a ductile deformation zone with a penetrative foliation and local mylonite zones. The Tally Ho shear zone is overprinted by late brittle faults, which
likely correspond to the northern extension of the Llewellyn fault. Previous work and this study demonstrate that brittle strike-slip deformation along the Llewellyn fault occurred between ca. 56 and 50 Ma.
Two unfoliated ca. 75 Ma granodiorite
intrusions crosscut the earlier ductile fabrics, which deform a ca. 98 Ma porphyry dyke in the Tally Ho shear zone and a ca. 98 Ma granodiorite pluton along its western limit, indicating that parts of the early ductile fabrics formed between ca. 98
and 75 Ma. At Bennett plateau, the Skarn Zone represents one of the 'early' gold mineralization styles consisting of an amphibole-sulphide skarn with structurally controlled quartz-actinolite-carbonate veins within metasedimentary rocks of the
Stuhini Group adjacent to Late (?) Cretaceous intrusions. A massive ca. 76 Ma dyke crosscuts the highly strained and hydrothermally altered host rock and hence provides a minimum age for the mineralization and ductile fabrics. To the south, the
Engineer mine is a structurally controlled epithermal vein system related to second-order splays of the Llewellyn fault. A ca. 54 Ma dyke is cut and offset by the main-stage veins and related fractures locally providing a maximum age for
mineralization. Vanadian-illite, dated at ca. 50 Ma and intergrown with gold from the Engineer vein constrains the timing of the main-stage veining and mineralization.
The ca. 20 Myr time-gap between the early and late deformation events and their
respective gold mineralization not only confirms these occurred at different times and at different structural levels, but also suggest they are related to distinct tectonic events. The intrusion-related and 'mesothermal' gold mineralization along
the Llewellyn-Tally Ho deformation corridor is associated with Late Cretaceous deformation and magmatism, and as such, is broadly coeval and analogous with some of the mineral occurrences of Dawson Range polymetallic belt in west-central Yukon. The
epithermal mineralization and late brittle event are related to the earliest Eocene magmatism and the Llewellyn fault, and match the timing and tectonic framework of the Juneau gold camp in southeastern Alaska. |
| Summary | (Plain Language Summary, not published)
The main objective of phase 5 (2015-2020) of Natural Resources Canada and Geological Survey of Canada's Targeted Geoscientific Initiative (TGI) program
was to generate new knowledge, methodologies and models to enhance the exploration industry's ability to detect buried ore deposits. This synthesis volume contains 20 individual papers that discuss craton to deposit-scale characteristics of
auriferous deposits, plus some support material pertaining to the TGI-5 Gold project. |
| GEOSCAN ID | 326039 |
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