Keele Research Repository

Detailed mapping of 100 sq.km, around the Corrieyairack Pass, Inverness-shire, has revealed the presence of two distinct lithostrati- graphic successions within dominantly psammitic metasediments. The two successions have been lithologically subdivided into nine formations.
The upper Corrieyairack Succession is overlain conformably by Leven Schists of the Lochaber Subgroup of the Dalradian, and is in tectonic contact with the lower Glenshirra Succession. Both successions are geochemically and lithologically distinct from the Lower Dalradian and are considered to be part of the Grampian Division.
Three episodes of deformation are recorded. An early phase is represented by minor isoclinal folds, a penetrative schistosity and the development of the Gairbeinn Slide, which now separates the two successions. A model suggesting the presence of major recumbent D1 folds is proposed based on evidence obtained from the Tarff Gorge.
The second episode of deformation, represented by major NE-SW trending tight, upright folds and abundant congruent minor folds with an axial planar cleavage, is the dominant control on the regional outcrop pattern. The third episode consisting of major N-S trending open folds is recognised on a macroscopic scale as a result of the variation in attitude and trend of the D2 structures.
A geochemical study of the metasediments and associated calc-silicate bands was undertaken in an attempt to distinguish between the different formations and successions and as an aid to the interpretation of the metamorphic and sedimentary histories of the area. There is a systematic variation in petrology and geochemistry between the two successions which is a product of original sedimentary differences.
Two principal metamorphic peaks have been recognised, both of middle amphibolite facies, with kyanite locally developed in semi-pelites and bytownite and clinopyroxene in calc-silicate bands, during in the southeast of the area.
A brief survey of the igneous rocks was also undertaken.