Abstract: We report here the results of U-Pb zircon analyses for samples collected during regional mapping of the northern Whitehorse trough. Three samples of the Nordenskiold formation, a crystal-rich volcaniclastic unit that occurs at several stratigraphic horizons in the Laberge Group, yielded concordant U-Pb zircon ages of 188.1 ± 0.4 Ma, 187.2 ± 0.4 Ma and 186.5 ± 0.3 Ma, respectively. These results clearly indicate multiple eruptive events rather than recycling of the volcaniclastic material. Zircons from a thin layer of ash tuff in the Tanglefoot formation (Laberge Group) yielded a concordant U-Pb age of 187.1 ± 0.7 Ma, confirming correlation with the Nordenskiold formation. A sample of porphyritic granite from the only pluton intruding the northern Whitehorse trough, near Carmacks, yielded a concordant U-Pb zircon age of 112.8 ± 0.2 Ma, whereas a precise age could not be resolved from zircons extracted from a porphyry dyke intruding the Tantalus Formation in the southern Whitehorse trough.

Authors: Colpron, M. and Friedman, R.M.

Keywords: geochronology, Tanglefoot formation, Tantalus Formation, Zircon dating

NTS Mapsheet(s): 105E, 105L, 115I, 115N

Citation: Colpron, M. and Friedman, R.M., 2008. U-Pb zircon ages for the Nordenskiold formation (Laberge Group) and Cretaceous intrusive rocks, Whitehorse trough, Yukon. In: Yukon Exploration and Geology 2007, Emond, D.S., Blackburn, L.R., Hill, R.P., and Weston, L.H. (eds.), Yukon Geological Survey, p. 139-151.

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