Continental rift zone magmatism

Abstract

Basaltic magmatism appears to be a common manifestation of extensional tectonics within continental plates. In Chapter 10 we focused our attention on the dominantly fissure-fed sub-alkaline (tholeiitic) flood basalt provinces, whereas in this chapter we shall concentrate on those more alkaline provinces, closely associated with rift/graben structures, fed from both fissure and central vent activity. As we have previously stated, this is a totally artificial subdivision, and in reality there is a complete spectrum of intracontinental plate magmatic activity, from extensive sub-alkaline flood basalt provinces to largely amagmatic graben structures with localized centres of alkaline volcanism.