Structure, metamorphism, and tectonism in the Soards Creek area, British Columbia

Rocks of the Neoproterozoic Horsethief Creek Group in the northern Monashee Mountains, southeastern British Columbia, have been exposed to P-T conditions up to 8 kbar and 750°C in the muscovite-out zone south of Soards Creek. Structural, stratigraphic, and metamorphic continuity has been established between the northern Monashee Mountains and the Selkirks to the east (Simony et al. 1980) and the Cariboos to the west (Pell and Simony 1987); this region is referred to as the Selkirk-Monashee-Cariboo Metamorphic Complex (SMC). This study verifies geologic continuity across the Columbia River at Mica Creek, and presents a reinterpretation of the Scrip Nappe (Raeside and Simony 1983), using new field data.;Recent work (e.g. Digel et al. 1998, Crowley et al. 2000, Gibson et al. 2005, Ghent and Villeneuve 2006) has revealed that metamorphic events occurred at 150-170 Ma, 120-135 Ma, 90-100 Ma, and 60-70 Ma. These events are not equally apparent in all parts of the SMC. Late Jurassic garnet grade metamorphism, preserved in the Encampment Creek area, was overprinted by Early Cretaceous kyanite-staurolite, kyanite, and sillimanite grade metamorphism, followed by middle-Cretaceous kyanite to sillimanite grade metamorphism south of Mica Creek. The "thermal front" of middle-Cretaceous metamorphism is likely within the kyanite-sillimanite zone in the Soards Creek area. A Paleocene thermal event introduced "pod sillimanite" west of the study area (Digel et al. 1998). These thermal events appear to have encroached on the region from the south and west. The heat source for these overprints is not yet known. Late-Paleocene to Early-Eocene uplift was likely related to thrusting on the underlying detachment surface; D3 buckle folds developed syn-tectonically.