Abstract: The Cassiar and Seagull batholiths are mainly post-tectonic felsic intrusions emplaced into the North American miogeocline and Yukon-Tanana Terrane, respectively, near the British Columbia-Yukon boundary. The two bodies range in composition from granodiorite and quartz monzonite to granite. Previous studies reported K-Ar and Rb-Sr dates of ~100 Ma for Seagull batholith and about 110 Ma for Cassiar batholith. Two samples of massive quartz monzonite from the interior of the Cassiar batholith, and a strongly foliated and lineated augen gneiss within a ductile shear zone near the western margin of the batholith, yield overlapping U-Pb monazite and/or zircon ages of 112.3 ± 2.0 Ma, 113.2 ± 2.2 Ma, and 110.2 ± 1.0 Ma respectively, by ID-TIMS methods. Samples of aplitic biotite granite and megacrystic biotite granite from the Seagull batholith give distinctly younger U-Pb zircon ages of 99.3 ± 2.2 Ma and 95.7 ± 2.1 Ma, respectively, using LA-ICP-MS methods.

Authors: Mortensen, J.K., Sluggett, C., Liverton, T., and Roots, C.F.

Keywords: geochronology

NTS Mapsheet(s): 105B

Citation: Mortensen, J.K., Sluggett, C., Liverton, T., and Roots, C.F., 2006. Uranium-lead ID-TI MS and LA-ICP-MS ages for the Cassiar and Seagull batholiths, Wolf Lake map area, southern Yukon. In: Yukon Exploration and Geology 2005, Emond, D.S., Bradshaw, G.D., Lewis, L.L., and Weston, L.H. (eds.), Yukon Geological Survey, p. 257-266.

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