Geochemistry and petrogenesis of volcanic clasts in the Permian breccias around Exeter

Abstract

Geochemical comparisons between volcanic clasts from the late Permian red beds and various granite plutons and granite porphyries ('elvans') from SW England show that the clasts have closest affinity with the poorly megacrystic granite of Dartmoor and the 'elvan-like' Godolphin granite. This affinity with the Dartmoor granite backs up recently published ɛ Nd data and age determinations. It is concluded that the clasts represent volcanic material derived from an evolving subsurface granitic magma, thereby conforming with conclusions/ideas of earlier workers for the former presence of a Dartmoor volcano.