Ainsworth Bluebell, Slocan, and Moyie camps. Mixing of lead from two different sources, both of which follow simple growth-curve lead evolution. The more radiogenic source is thought to represent evolution of lead in the upper crustal, continentally derived sedimentary rocks which host these deposits. The two-stage Bluebell growth curve provides an estimate of the uranium-poor lead source which may be the lower crust, the upper mantle, or a mixture of both. Mixing line isochrons drawn between these two curves at ages corresponding to the best estimates for the mineralization ages at these three mining camps closely fit the lead isotope data. This supports the age estimates for all three camps and, in particular, substantiates a Lower Cambrian age for the original mineralization in the Ainsworth and Bluebell deposits. Mixing is assumed to take place at the time of mineralization and may be attributed to magmatic activity in the Moyie and Slocan camps. Applicability of the model to a large part of the Omineca Belt. May be used to date both epigenetic and syngenetic or penecontemporaneous deposits of unknown age.--Modified journal abstract.

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