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TitleSuperimposed Late Cretaceous and earliest Eocene gold mineralization and deformation events along the Llewellyn-Tally Ho deformation corridor in northwest British Columbia and southern Yukon
LicencePlease note the adoption of the Open Government Licence - Canada supersedes any previous licences.
AuthorCastonguay, SORCID logo; Ootes, L; Devine, F; Friedman, R
SourceTargeted Geoscience Initiative 5: contributions to the understanding of Canadian gold systems; by Mercier-Langevin, P (ed.); Lawley, C J MORCID logo (ed.); Castonguay, SORCID logo (ed.); Geological Survey of Canada, Open File 8712, 2020 p. 223-236, Open Access logo Open Access
PublisherNatural Resources Canada
Documentopen file
Mediaon-line; digital
RelatedThis publication is contained in Targeted Geoscience Initiative 5: contributions to the understanding of Canadian gold systems
RelatedThis publication is related to Superimposed auriferous structural events along the Llewellyn-Tally Ho deformation corridor in southern Yukon and northwest British Columbia
File formatpdf
ProvinceBritish Columbia; Yukon
NTS104M/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
AreaCarcross; 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
Subjectseconomic 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
Illustrationslocation maps; geoscientific sketch maps; photographs; cross-sections; tables; geochronological charts
ProgramTargeted Geoscience Initiative (TGI-5) Gold ore systems
Released2020 06 11; 2023 03 17
AbstractA 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.

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