The Petrogenesis of Hornblende-mica-lamprophyre Dykes at South Hill, Jersey, C. I.

Abstract

AbstractAt South Hill, 1/2 mile south-east of St. Helier, two hornblende-mica-lamprophyre dykes cut the Fort Regent granophyre. They are themselves displaced by two gently dipping shear zones and a dolerite dyke belonging to the main Jersey dyke swarm cuts the granophyre, lamprophyres, and shears, Petrographically the lamprophyres are of the spessartite-kersantite type, but the presence of euhedral brown amphibole invites comparison with the camptonites. The genesis of the lamprophyres is discussed and a significant role is assigned to volatile constituents.