Abstract: The 1.71 Ga Bonnet Plume River intrusions (BPRI) and related volcanics are preserved only as clasts in the 1.60 Ga Wernecke breccias of Yukon that host iron-oxide copper gold (IOCG) occurrences. Field work conducted in 2009 confirmed that they did not intrude the surrounding <1.64 Ga Wernecke Supergroup. Petrography shows that they are extensively altered and/or metasomatized, although relicts of primary igneous minerals remain. The major oxides are of little use in classification. Trace element geochemistry however, reveals a mafic to intermediate, calc-alkaline volcanic arc signature. Geochemical modelling has demonstrated that crystal fractionation was dominated by pyroxenes, plagioclase and olivine. The BPRI and related volcanic rocks are thought to have originated in a calc-alkaline volcanic arc that was obducted onto the Wernecke Supergroup, subsequently partially brecciated, and finally sank within the Wernecke breccias to the level of the Wernecke Supergroup.

Authors: Nielsen, A.B., Thorkelson, D.J., Marshall, D.D. and Gibson, H.D.

Keywords: geochemical modelling, metasomatized, Wernecke breccias, Wernecke Supergroup

NTS Mapsheet(s): 116G

Citation: Nielsen, A.B., Thorkelson, D.J., Marshall, D.D. and Gibson, H.D., 2011. Paleoproterozoic Bonnet Plume River intrusions: Evidence for a calc-alkaline arc at 1.7 Ga and its partial preservation in Yukon, Canada. In: Yukon Exploration and Geology 2010, MacFarlane, K.E., Weston, L.H., and Relf, C. (eds.), Yukon Geological Survey, p. 183-196.

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