A contribution to the petrology of the Great Dyke of Nova Scotia

Abstract

A large steeply dipping, quartz-diabase dyke, over 170 miles long and up to 600 feet wide, cuts Paleozoic rocks in southwestern Nova Scotia. The main minerals are labradorite, pyroxene, quartz: alkali-feldspar and accessory magnetite, ilmenite, biotite and amphibole. The contacts show a chilled margin against relatively unmetamorphosed country rock. Chemical analyses indicate that the rock is derived from a tholeiitic magma slightly deficient in ferro-magnesian constituents. Indications are that the dyke was intruded in the late Triassic into a tension fissure. Potassium-argon date of the chilled margin of the dyke indicates194 m.y. The dyke is correlated with the North Mountain basalts of the Acadian Triassic basin on the basis of age, lithology and chemistry.