Abstract: The Rau deposit in central Yukon is a gold-rich carbonate replacement deposit hosted in mid-Paleozoic carbonate rocks of the Mackenzie Platform in the footwall of the Dawson thrust. Gold-bearing sulphide mineralization is peripheral to a zone of hornfels and local tungsten-bearing skarn that is associated with several small bodies of granitic aplite and pegmatite that have yielded 40Ar/39Ar muscovite ages of 62.3 ± 0.7 Ma, 62.4 ± 1.8 Ma and 59.1 ± 2.0 Ma. These intrusions are geochemically different and slightly younger than the 65.2 ± 2.0 Ma McQuesten plutonic suite farther to the south. Most Pb isotopic analyses of sulphides from the Rau deposit cluster within compositions of igneous feldspars from the associated intrusions; however, some analyses fall on a trend toward more radiogenic compositions that were determined for the host carbonate rocks. The data are consistent with the Rau sulphide mineralization being genetically related to the early Paleocene felsic intrusions, and forming peripheral to more proximal zones of hornfelsing and tungsten-bearing skarns.

Authors: Kingston, S., Mortensen, J.K., Dumala, J.K., and Gabites, J.

Keywords: carbonate rocks, Dawson thrust, Mackenzie platform, McQuesten plutonic suite, mineralization, Rau deposit, skarn

NTS Mapsheet(s): 106D

Citation: Kingston, S., Mortensen, J.K., Dumala, J.K., and Gabites, J. , 2010. Ar-Ar geochronology and Pb isotopic constraints on the origin of the Rau gold-rich carbonate replacement deposit, central Yukon. In: Yukon Exploration and Geology 2009, MacFarlane, K.E., Weston, L.H. and Blackburn, L.R. (eds.), Yukon Geological Survey, p. 213-222.

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