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Structural relations between the Shuswap and "Cache Creek" complexes near Kalamalka Lake, southern British Columbia Solberg, Peter Harvey

Abstract

Five phases of deformation are recognized in Shuswap metamorphics south of Vernon, British Columbia. Phase 1 and 2 deformations are isoclinal gently dipping folds which trend N and ESE respectively. Some thermal activity may have occurred prior to phase 2 deformation but metamorphism culminated in the amphibolite facies during and following phase 2. Metamorphism waned prior to the development of NE trending phase 3, folds of which are angular and moderately tight with one steep and one shallowly dipping limb. Phase 4 and 5 deformations trend NE and N respectively, and comprise open upright buckle folds and fractures which are contemporaneous with abundant hydrothermal alteration. The 42- 10 m.y. B.P. sr/Rb whole rock age date secured from a phase 2 sill probably represents thermal upgrading. Low metamorphic grade "Cache Creek" metasediments west of Vernon have undergone 4 recognized deformational phases. Phase 1 folds are tight, steeply dipping, and trend WNW. Phase 2 comprises E trending, angular mesoscopic folds. Phase 3 and 4 comprise NE and N trending fracture sets. A large amphibolite sill defines the "Cache Creek" albite-epidote-amphi-bolite facies metamorphic culmination. Metamorphic hornblendes from the amphibolite yield a 178 + 6 m.y. B.P. age date, using the K/Ar method. Hydrothermal activity occurred in association with phase 3 and 4 deformations. The final four phases of Shuswap deformation appear to correlate with respective "Cache Creek" phases, based on structural similarities. This suggests that the two complexes may be, at least in part, structural equivalents.

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