Pressures and temperatures have been determined from locations in the eastern Dalradian using a number of different geothermometers and geobarometers. Temperatures range from 550°C in the low kyanite zone to about 800°C in the sillimanite–K feldspar zone. Pressures range from about 5.5 kbar in Glen Esk to 9–10 kbar in the Central Highlands. The barometric calibrations employed are consistent with the kyanite–sillimanite equilibrium. Evidence from mineral zoning suggests that rocks outside the Buchan area (in the Duchray Hill Gneiss, Glens Clova and Avon and in the Schichallion area) underwent a pressure decrease synchronous with the metamorphic peak. Regional temperature variations define a thermal high centred on the Cromar–Glen Muick–Duchray Hill Gneiss area. To the W of this high temperatures decrease rapidly. A sharp thermal break occurs between high grade sillimanite–K feldspar gneisses in Glen Muick and kyanite–staurolite schists to the W. This thermal contrast is attributed to a structural break which may be analogous to a number of other thermal features in the Dalradian.

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Metamorphic conditions of 8 ± 1.5 kbar and 820 ± 50°C are estimated for garnet-clinopyroxene-bearing mafic granulites and associated garnet-sillimanite migmatitic gneisses from the Dalradian sillimanite zone. Revised estimates for the kyanite zone in Glens Avon and Ey (W of the regional andalusite and sillimanite zones) are c . 7 kbar at 500-600°C. Results from rocks close to the kyanite-sillimanite isograd in Glen Clova testify to the accuracy of the barometric calibrations. Textural indications are that sillimanite preceded andalusite in the Glen Muick area: in this region the kyanite-andalusite isograd has no reality. In Glen Muick sillimanite grew synchronously with the development of the dominant steep foliation, and as part of a progressive evolution in metamorphic conditions, not as a separate late overprint. The western segment of the kyanite-andalusite isograd is thought to have developed before the attainment of the P-T conditions recorded in rocks from Glens Avon and Ey. Metamorphic and geochronological data are examined in the light of the Banff Nappe hypothesis. It is suggested that the eastern high-temperature zones were thrust over the present western kyanite zone and that rocks to the W of the kyanite-andalusite isograd were metamorphosed by thermal relaxation beneath this thrust sheet.

The preserved array of pressures in the eastern Dalradian indicates that considerable syn-to post-metamorphic differential uplift has occurred. This inferred differential uplift suggests that Buchan sillimanite zone rocks originally lay at higher structural levels than presently adjacent cooler kyanite zone rocks to the west. A number of features are believed to coincide with the western margin of the sillirnanite zone. These are a maximum in temperature, sharp thermal features, a high strain zone, and a train of metabasites. These features are explained by invoking synmetamorphic movement between the Buchan sillimanite zone and the kyanite zone to its west, involving some horizontal component of movement. It is suggested that the lateral, now eroded, equivalents of the Buchan area once provided part of the required tectonic thickening for other parts of the Dalradian. Areas surrounding the Buchan area suffered tectonic burial followed by metamorphism during uplift relative to the Buchan area.

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