Abstract

U–Pb dates from zircons indicate that plutonic events occurred during the Paleozoic in the Omineca Crystalline Belt in southeastern British Columbia. In the Kootenay Arc, granitoid cobbles in conglomerate of the Carboniferous Milford Group were derived from quartz monzonite and diorite plutons of probable Ordovician age. Near Little Shuswap Lake, gneissic granitoid units have yielded Cambro-Ordovician ages. At least one episode of deformation affected country rocks of unknown age before intrusion. In the Monashee Complex south of Thor–Odin Nappe in South Fosthall Creek, lineated quartz monzonite is of probable Ordovician age. Comparison of fabrics suggests that at least one episode of metamorphism and deformation occurred prior to intrusion. No clear relationship between the cobbles and these plutons can be demonstrated because major faults lie between them, but substantial revision to accepted models of Paleozoic paleogeography of this region will have to be made. In the Clachnaeudainn tectonic slice east of the Monashee Complex, granitic gneiss is of Paleozoic, possibly Siluro-Devonian, age. This pluton appears to be involved in all phases of deformation that affected its country rocks. Near Quesnel Lake, parts of a composite gneissic granitoid pluton appear to be of Devonian or earliest Carboniferous age.

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