Layered ultramafic rocks within the Borralan Complex, Scotland

Synopsis Ground magnetic survey has delineated a 5000 γ anomaly over part of the south-western margin of the Borralan Complex. Drilling across the anomaly has revealed a suite of pyroxenites, cromaltites, and hornblendites similar to rocks known at outcrop and in addition olivine-, phlogopite-, diopside-, and tremolite-rich rocks not hitherto known from Borralan. Whole rock chemistry indicates a similarity to several other complexes. While textural and lithological evidence, including fine-scale layering, support a cumulus igneous origin for the pyroxenites, hornblendites, and olivine rocks, some or all of the other types are most probably due to metasomatic processes near the contact with marble.