Yukon‑Tanana Terrane

Yukon‑Tanana Terrane
Name	Yukon‑Tanana Terrane
Type	Terrane
Region	Yukon, Alaska, British Columbia
Coordinates	64°N 138°W

Yukon‑Tanana Terrane The Yukon‑Tanana Terrane is an accreted geological tract in northwestern North America encompassing parts of Yukon, Alaska, and British Columbia. It underlies extensive exposures of Paleozoic to Mesozoic rocks adjacent to the North American Plate, the Fairweather Fault, and the Tintina Fault, and is important to studies of terrane accretion, regional mineralization, and Cordilleran tectonics. The terrane is bounded by major structural features such as the Denali Fault, the Kluane Ranges, and the Ogilvie Mountains and has been the focus of geological mapping by agencies including the United States Geological Survey, the Geological Survey of Canada, and university teams from University of Alaska Fairbanks and University of British Columbia.

Geological setting and extent

The Yukon‑Tanana Terrane occupies a swath extending from the Aleutian Range margin near Cook Inlet through interior Alaska across Yukon into northern British Columbia, juxtaposed against the Cache Creek Terrane, the Alexander Terrane, and the Wrangellia Terrane along sutures defined by the Denali Fault and the Tintina Fault. Its map expression includes the Tanana River basin, the Whitehorse Trough, and the Big Salmon Range, and it overlies basement domains traditionally correlated with the Northwest Territories and the Canadian Shield in paleogeographic reconstructions used by researchers at the Smithsonian Institution and the Royal Society of Canada. Regional correlations invoke paleomagnetic work tied to the Geological Society of America and stratigraphic comparisons used in syntheses prepared for the Intergovernmental Panel on Climate Change paleogeography sections.

Lithology and stratigraphy

Exposures in the terrane comprise heterogeneous assemblages of metasedimentary and metavolcanic sequences including schist, phyllite, quartzite, and amphibolite, intruded by granitic plutons of Ordovician to Jurassic age mapped by the United States Geological Survey and the Geological Survey of Canada. Notable stratigraphic packages include carbonate units, turbidites, and volcaniclastics correlated with sequences described in studies from Yale University, Harvard University, and the University of Cambridge, and fossiliferous horizons that have been compared to assemblages from the Appalachian Mountains, the Caledonides, and the Siberian Platform in efforts by paleontologists at the Natural History Museum, London. Detrital zircon geochronology performed at laboratories such as the Isotope Geochemistry Laboratory, University of British Columbia and the Arizona LaserChron Center has constrained depositional ages and provenance, linking parts of the terrane to sources proposed in studies associated with the Lamont–Doherty Earth Observatory and the Max Planck Institute for Chemistry.

Tectonic history and evolution

Tectonic reconstructions interpret the terrane as having formed through a complex history of rifting, arc magmatism, subduction, and accretion during the Paleozoic and Mesozoic, with models advanced by scientists affiliated with the Geological Society of America, the American Geophysical Union, and the Canadian Society of Petroleum Geologists. Proposed scenarios involve displacement along major strike‑slip faults like the Denali Fault and interactions with exotic blocks such as the Alexander Terrane and fragments correlated with the Insular Superterrane, as discussed in papers by researchers from the University of Alaska Fairbanks and the University of Toronto. Paleomagnetic and structural studies published in journals of the European Geosciences Union and the Geological Magazine have debated whether parts of the terrane originated near the Paleo‑Pacific Realm or were proximal to the Laurentian margin before transcurrent transport linked to events recorded at the Laramide Orogeny and the Sevier Orogeny.

Metamorphism and structural features

Metamorphic grades within the Yukon‑Tanana Terrane range from greenschist to amphibolite facies, with localized higher‑grade zones identified in structural studies by teams at the University of Saskatchewan and the University of Calgary. Barrovian and contact metamorphism associated with syn‑ to post‑tectonic intrusions from plutons correlated with the Coast Plutonic Complex have produced mineral assemblages analyzed by researchers at the Geological Survey of Canada and the USGS Alaska Science Center. Structural mapping documents recumbent folds, north‑ and south‑vergent thrusts, and mylonitic fabrics related to strike‑slip motion along the Tintina Fault, the Fairweather Fault, and subsidiary splays explored in monographs from the American Association of Petroleum Geologists and case studies conducted by the Canadian Journal of Earth Sciences.

Economic geology and mineralization

The terrane hosts diverse mineral deposits including orogenic gold, polymetallic vein systems, porphyry copper‑gold occurrences, and skarn assemblages studied by the British Columbia Ministry of Energy, Mines and Petroleum Resources and the Yukon Geological Survey. Prominent mining districts and prospects within or adjacent to the terrane have attracted companies listed on the Toronto Stock Exchange, the NASDAQ, and the London Stock Exchange, and have been the focus of mineral exploration by firms collaborating with the Canadian Mining Innovation Council and the Alaska Industrial Development and Export Authority. Geochemical studies conducted at labs like the Geological Survey of Canada geochemistry facility and the USGS National Minerals Information Center have documented pathfinder elements and alteration halos similar to deposits in the Carlin Trend, the Porgera field, and the Kennecott mines studied in comparative economic geology syntheses.

Research history and controversies

Research on the Yukon‑Tanana Terrane has involved multiple generations of fieldwork, mapping campaigns, and analytical advances led by institutions such as the United States Geological Survey, the Geological Survey of Canada, the University of Alaska Fairbanks, and the University of British Columbia. Controversies have centered on its paleogeographic origin, the magnitude and timing of strike‑slip displacement along the Tintina Fault, and correlations with terranes like the Alexander Terrane and Wrangellia Terrane debated in symposia of the Geological Society of America and papers in the Journal of Geophysical Research. Ongoing debates continue in conference proceedings of the American Geophysical Union and collaborative projects funded by agencies including the Natural Sciences and Engineering Research Council of Canada and the National Science Foundation.

Category:Geology of Yukon Category:Terranes of North America