Mineralogy and geochemistry of proterozoic basaltic intrusions, Spionkop Ridge, southwestern Alberta

Three suites of basaltic intrusions occur on Spionkop Ridge in southwestern Alberta. The oldest consists of glomeroporphyritic, alkaline sills and dik es offset by Proterozoic faults, along which a second generation of amygdal oidal alkaline to transitional dikes have been emplaced. The youngest is a tholeiitic diabasic sill containing abundant epidote. The basaltic suites c an be distinguished by their TiO2, Al2O3, P2O5 and Yb concentrations. The g lomeroporphyritic intrusions have similar to 3.7% TiO2, 15% Al2O3, 0.74% P2 O5 and 4.1 ppm Yb, the amygdaloidal intrusions similar to 2.5% TiO2, 16% Al 2O3, 0.47% P2O5 and 3.3 ppm Yb, and the diabasic intrusions similar to 4% T iO2, 12% Al2O3, 0.49% P2O5 and 2.4 ppm Yb. Petrographic and geochemical dat a for similar intrusions and lava flows from locations throughout the Lewis Thrust Sheet are consistent with this three-fold subdivision.