Description

From Hildreth and others (2007) ^[1] : "About 10 km southwest of Blue Mountain, an isolated 0.38-km-square-area exposure of olivine-basaltic lava (50 weight percent SiO2, 7 weight percent MgO) forms a subdued, glacially scoured ridge (Lone basalt) that rises 80 m above the surrounding muskeg. The rock contains 5 to 8 volume percent olivine phenocrysts (0.5-2 mm diam) and sparse oxide microphenocrysts in a holocrystalline groundmass of intergrown plagioclase laths and equant grains of olivine, oxides, and rare clinopyroxene. This subalkaline basalt is similar to, but not quite as primitive as, the basalt of Ukinrek Maars. It differs compositionally, however, from the mafic rocks of nearby Mount Peulik ^[2] and from those of the other arc-front centers nearby, and is not demonstrably related to Blue Mountain dacite. Nonetheless, the composition of the Lone basalt is not far from that of the mafic enclaves in Blue Mountain dacite, nor from that of the 500-ka subalkaline basaltic cone at Gertrude Creek northeast of Becharof Lake. Wilson and Shew (1992) ^[3] determined a whole-rock K-Ar age of 593+/-73 ka for the Lone basalt.