Abstract: Paleomagnetic conglomerate tests were run at three localities in the Conglomerate formation of the Jurassic Laberge Group in the southern Yukon. The localities are located within the Whitehorse Trough about 5, 20 and 40 km east of its margin with the intruded Coast Plutonic Complex. At each locality, 2.5-cm-diameter cores were drilled from 32 clasts of mainly igneous provenance and 8 more from the conglomerate matrix, totaling 120 cores, and yielding 190 specimens in all. The specimens were analysed using standard paleomagnetic demagnetization and testing techniques. The matrix, mostly greywacke in composition, yields characteristic remanent magnetization (ChRM) directions carried by pyrrhotite that give coherent steep downward directions. The clasts, at all three localities, yield paleomagnetic conglomerate tests that show statistically random ChRM directions. This leads to the conclusion that the clasts were not remagnetized by the event that remagnetized the matrix, which was likely caused by hydrothermal fluid flow during the Late Cretaceous to Eocene Laramide Orogeny. Furthermore, these conclusions support earlier studies by demonstrating that felsic plutons in the Whitehorse Trough likely carry primary ChRM directions, e.g., the 75 Ma Mount Lorne stock, the 109 Ma Mount McIntyre pluton, the 112 Ma Whitehorse batholith, and the 186 Ma Teslin Crossing stock.

Authors: Harris, M.J., Symons, D.T.A., and Hart, C.J.R.

Keywords: Coast Plutonic Complex, geophysics

NTS Mapsheet(s): 105D

Citation: Harris, M.J., Symons, D.T.A., and Hart, C.J.R., 2002. No remagnetization in plutonic rocks of the Whitehorse Trough, southern Yukon: An extensive paleomagnetic conglomerate test. In: Yukon Exploration and Geology 2001, Emond, D.S., Weston, L.W., and Lewis, L.L. (eds.), Exploration and Geological Sciences Division, Yukon Region, Indian and Northern Affairs Canada, p. 111-124.

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