A stable isotope and petrographic study of the alkaline volcanic rocks related to continental extension in White Lake Basin of South-Central British Columbia

White Lake Basin in south-central British Columbia is the location of a well-exposed suite of early Tertiary analcime-bearing alkaline volcanic rocks associated with continental extension. The delta18 O values of these rocks (delta18O = +2.8 to +7.35), closely mirror the Coryell Suite (delta18O = +3.5 to +8.0), proving a cogenetic match between the volcanics and the parent magma. Rapid ascent of magma is confirmed in several petrographic thin section by "seive" textures within the abundant feldspar groups. Mineral assemblages indicate rapid magma ascent at high temperature. End-members of feldspar series show variation from sodic to potassic as the magma ascended, which indicates a primary source more sodic and matching with the cogenetic Coryell Suite. Data analyzed in this study provides proof that the parent magma for the White Lake Basin volcanics is the same material from the intrusive Coryell Suite.