Tourmalinization in the Dartmoor granite

Abstract

On the basis of field relationships, the main types of the Dartmoor granite can be referred to four stages of intrusion, the sequence being from relatively basic to thoroughly acid.To this sequence is closely related an increase in the content of tourmaline and in the extent to which autopneumatolysis (with tourmalinization) was effective before solidification of the rock was complete.Autopneumatolysis is well displayed by many minor intrusions referred to the latest stage. Such an intrusive rock is reddened more or less uniformly throughout its entire mass, and volatile constituents exhaled from its margin have reddened a contact-zone of the grey granite into which it is intrusive.