The Schichallion complex is situated in the Central Highlands of Scotland between the villages Struan and Kinloch Rannoch. The area is of considerable geological interest and has been investigated stratigraphically and structurally by E. M. Anderson and Bailey and McCallien. As a consequence of their researches a complete stratigraphical succession has been established. Thus, the metamorphic rocks of the area are classified into the Moinian and Dalradian systems, which are separated by a plane of tectonic discontinuity known as the Boundary Slide. The Moinian rocks are quartz-felspathic granulites, whereas the Dalradian system includes pelitic schists, quartzites, limestones as well as a variety of meta-igneous rocks.

In his previous research the present author has established the tectonic history of the complex. In particular three episodes of folding (F1 to F3) and a much later episode of faulting (F4) were recognized. Of these the F3 episode is of least significance. Consequently, events after the F2 movements can be in many cases regarded as post-folding.

The present contribution is concerned essentially with the mapping of the metamorphic zones (garnet and staurolite-kyanite) and with a detailed study of the mineralogical evolution of regionally metamorphosed rocks within these zones.

In the field it is possible to prove that the staurolite-kyanite zone is essentially post-folding, since the kyanitepegmatites are found to cut across the minor F2-folds. In this respect textural studies confirm the field observations. The study of the internal inclusions in garnets indicates that the garnet zone has a much longer history, since pre-F2 garnets are found in the southern part of the complex and throughout the central part of the area syn-tectonic F2 garnets are apparent. The pre-F2 garnets contain a very fine-grain F1 fabric. Hence the garnets in relation to the F1 movements are post-tectonic. Thus, the regional metamorphism can be subdivided into three phases: the F1 metamorphism, the F2 metamorphism and the post-F2 metamorphism. The latter, on structural evidence appears to be at least in part contemporaneous with the F3 movements.

The meta-igneous rocks of the area are grouped into the hornblende-schists and granular epidiorites. The hornblende-schists appear to have suffered deformation and recrystallization during F1 and F2 episodes of movement. On the other hand the granular epidiorites are later than the F1 and the F2 movements. Although in the southern parts of the district the epidiorites have been slightly deformed, elsewhere they preserve the original ophitic texture and cut across the F1 and F2 folds. The deformation in the south is attributed to the effects of the F3 folding. The epidiorites have been evidently emplaced as dolerites after the F2 movements and before the F3 metamorphism.

The localized retrogressive metamorphism is associated with the F4 movements, which are responsible for the Loch Tay Fault. The Fault is later than the minor intrusives associated with the Younger Granites of the Scottish Highlands and is suggested to be of a Lower or Middle O.R.S. age.

On the basis of the chemical composition of the plagioclase felspars it is proposed to include all the staurolite and kyanite bearing rocks into the epidote-amphibolite facies. In this respect temperature and the hydrostatic pressure are assumed to have been the main factors, since similar minerals came into existence during static and dynamic stages of metamorphism alike.