Geochronology of Selected Igneous Rocks in the Alberta Rocky Mountains, with an Overview of the Age Constraints on the Host Formations

This report presents preliminary results of the first attempt at systematic sampling and dating of igneous rocks cropping out in the Alberta Rocky Mountains and Foothills. The Alberta Rocky Mountains expose over 1.4 billion years of stratigraphy from the Mesoproterozoic Purcell Supergroup to Cenozoic strata of the Paskapoo Formation, and encompass a huge area approximately 700 km in length and 50 to 120 km wide. Occurrences of igneous rocks in the Alberta Rocky Mountains are very limited (except for its southernmost portion, the Clark Range) and their ages poorly constrained.

From the southern Alberta Rockies, we have sampled selected Purcell mafic sills, felsic alkaline sills, and the Crowsnest alkaline volcanic suite. In addition, we have sampled the three known occurrences of small, isolated, hypabyssal mafic rocks in the northern and central Alberta Rocky Mountains.