III.— The Petrology of the Ben Vrackie Epidiorites and their Contact Rocks

Abstract

I. HISTORY OF PREVIOUS WORK AND GEOLOGICAL SETTING Ben Vrackie (2,757 feet) is a conspicuous hill in the Perthshire Highlands, about two and a half miles east of the Pass of Killiecrankie. The country rocks belong to the Dalradian series, and are in the garnet zone of metamorphism. The stratigraphical succession in the district was elucidated by Bailey (1925, p. 673 and 1930, p. 90). Within the Dalradian series, there occur a number of metamorphosed basic intrusions known as epidiorites and such rocks are well-developed at Ben Vrackie. The epidiorites at this locality and their contact rocks were described by Barrow and others in the Geological Survey memoir on the Blair Atholl, Pitlochry and Aberfeldy district (1905, pp. 77, 79). Wiseman, following his study of the progressive metamorphism of epidiorites, remapped most of the area at Ben Vrackie where such rocks are found. The present map (Fig. 1) incorporates his work, and extends it for short distances to the east and south. The northern part of the map area is largely occupied by epidiorite and Ben Lawers Schists. In the east, the outcrop of the latter formation joins the main belt of Ben Lawers Schists, which runs north-east and south-west, and crosses the Ben Vrackie massif about half a mile south-east of the summit. On the north, west and south, the northern area of Ben Lawers Schists is bounded by an extensive development of the Ben Eagach Schist, with some epidiorite and quartzite. These rocks are involved in folding on This 250-word extract was created in the absence of an abstract In conclusion, the writer wishes to express his thanks to Professor C. E. Tilley, Dr. S. R. Nockolds and Professor K. C. Dunham, under whose guidance the work was carried out. He further wishes to thank Professor T. Neville George and Dr. B. C. King for helpful criticism of the script. The writer is greatly indebted to Dr. J. D. H. Wiseman for access to field maps covering the greater part of Ben Vrackie, and for the loan of rock specimens and thin sections. Finally, he desires to thank Trinity College, Cambridge, for the tenure of the Lees Knowles Exhibition during the first two years of the work.