Paper No. 7
Presentation Time: 9:50 AM


ALLAN, Murray M.1, MORTENSEN, James K.2, HART, Craig J.R.3 and SÁNCHEZ, Matías G.3, (1)Mineral Deposit Research Unit, University of British Columbia, 2020 - 2207 Main Mall, Vancouver, BC V6T1Z4, Canada, (2)Earth and Ocean Sciences, University of British Columbia, Vancouver, BC V6T 1Z4, Canada, (3)Mineral Deposit Research Unit, University of British Columbia, 2020 - 2207 Main Mall, Vancouver, BC V6T 1Z4, Canada,

The 2009-2012 exploration boom in the Yukon's White Gold and Dawson Range districts has facilitated an updated metallogenic framework for the northern Yukon-Tanana Terrane (YTT) of Yukon and Alaska. Numerous metallogenic events are recognized, including syngenetic, magmatic-hydrothermal, and orogenic styles of mineralization.

Syngenetic SEDEX Pb-Zn and VMS Pb-Zn-Cu-(Ag-Au) mineralization is associated with Devono-Mississippian and Late Permian phases of YTT arc construction, and has been overprinted by strong ductile deformation and low-grade metamorphism in the latest Permian. Six magmatic-hydrothermal metallogenic events are superimposed on the YTT: (1) syn- to post-metamorphic anatectic melts in the Late Permian (253 – 250 Ma) are accompanied by sparse gold mineralization; (2) Cu-Au mineralization formed during Early Jurassic (200 – 179 Ma) magmatism, and was accompanied by rapid crustal exhumation (e.g., Minto); (3) Au-mineralized breccias, skarns, epithermal systems, and polymetallic veins are associated with mid-Cretaceous (115 – 98 Ma) magnetite-series arc magmas in the Dawson Range; (4) variably Cu- and Au-rich porphyry systems intrude the mid-Cretaceous arc in the early Late Cretaceous (79 – 72 Ma; e.g., Casino); (5) porphyry Mo and Cu systems and Ag-rich polymetallic veins, carbonate-replacement, and skarn bodies are temporally and spatially associated with northeast-trending, sinistral fault systems in the latest Cretaceous (72 – 67 Ma); and (6) Cu-Pb-Ag skarn, and Au-Ag epithermal systems are associated with dominantly felsic Paleocene-Eocene (60 – 55 Ma) magmas emplaced into zones of extension associated with the Tintina fault zone.

Orogenic gold formed in exhuming crust during a Middle to Late Jurassic (163 - 155 Ma) magmatic lull, and was structurally controlled by small-displacement sinistral fault zones, high-angle reverse faults, and kink folds. This event is responsible for the recent gold discoveries of the White Gold district, and accounts for the majority of western Yukon’s placer gold endowment. A subsequent episode of orogenic gold mineralization (96 – 92 Ma) formed in structures that post-date emplacement of mid-Cretaceous granitoids along the Dawson Range.

  • MMA_GSADenver_2013.pdf (10.4 MB)