Isotopic age of the Nevadan orogeny and older plutonic and metamorphicevents in the Klamath Mountains, California

Abstract

Several metamorphic and plutonic events have been recognized on thebasis of K-Ar and Rb-Sr mineral and whole-rock ages. The primarymetamorphism of the Abram's Mica Schist and the co-extensive SalmonHornblende Schist was approximately 380 m.y. ago (Devonian), based onstrontium evolution diagrams. The Stuart Fork Formation, the schistsof Condrey Mountain, and related schists were produced during Middleand Late Jurassic metamorphism. The Pit River stock, grouped with theCastle Crags pluton, has a minimum age of 246 m.y. (Permian). Threeother plutonic groups are Middle to Late Jurassic, as follows: 165 to167 m.y., 145 to 155 m.y., and 127 to 140 m.y. The Nevadan orogeny ishere restricted to the Middle and Late Jurassic deformational,metamorphic, and plutonic events.

38 samples from this reference