Abstract

A revised metamorphic history for the Chiwaukum Schist, North Cascades, Washington, consisting of dynamic contact metamorphism of Buchan style associated with the Mount Stuart batholith, followed closely by regional metamorphism of Barrovian style, is similar to that for rocks adjacent to the Sloan Creek intrusion 30 km to the north, and on the opposite (west) side of the Straight Creek/Fraser River fault system, to the Settler schist in the vicinity of the Spuzzum and Scuzzy intrusions 200–270 km north in British Columbia. The Late Cretaceous regional increase in lithostatic pressure implied by this history, whether caused by tectonic or magmatic processes, may be the same as that responsible for the crystallization of magmatic epidote in certain other intrusives in the North Cascades such as the Tenpeak. More radiometric crystallization ages as opposed to cooling ages are needed to resolve this point.

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