OCCURRENCE OF A SHEETED DOLERITE DYKE COMPLEX IN THE BALLANTRAE OPHIOLITE, SCOTLAND

A sheeted dolerite dyke swarm has been discovered at Duniewick Fort, B allantrae. It forms part of the Early Ordovician Ballantrae Complex of Ayrshire, southwest Scotland. Asymmetric chilled margins, parallel to sub-parallel dykes and multiple dykes (dykes within dykes) are found. Although the mineralogy has been altered by metamorphism, the geochem istry is comparable with modern day back-are marginal basin basalt. Cr oss-cutting sills have the chemistry of within-plate basalt. The regio nal geological setting suggests that an ophiolite sequence has been di smembered and incorporated into a serpentinite melange. This is the fi rst description of a 100% sheeted dyke complex (senso stricto) from th e Ballantrae ophiolite.