Ultramafic inclusions in anorthite megacrysts from the Isle of Skye

1–15 μm diameter ultramafic inclusions in anorthitic plagioclase megacrysts from Skye were analyzed by electron microprobe and tentatively identified as sub-calcic augite, or sub-calcic augite submicroscopically intergrown with amphibole. The inclusions nucleated in Ca-Al-depleted, Fe-Mg-H₂O-enriched magma adjacent to the interface between plagioclase crystals and basalt and were rapidly enveloped by the growing plagioclase. The inclusions may be important in the fractional crystallization of the Skye alkali olivine basalt suite.