IV.—The Plutonic Rocks of Garabal Hill

Abstract

This complex of igneous rocks lies between Ardlui, at the head of Loch Lomond, and the head of Loch Fyne. In 1892 it was the subject of a fairly exhaustive paper by Teall & Dakyns, but in view of a number of new facts which we have discovered we venture to submit a re-examination of the problems connected with the complex. The mass is broken by a north-east fault. The country to the west of this fault is mainly porphyritic granite and tonalite; to the east there is tonalite and also more basic diorite and ultrabasic rocks. We shall concern ourselves mainly with the basic and ultrabasic groups, as they are somewhat unusual in the “Newer Plutonic Rocks of the Highlands”.