The Older Ortho-gneisses of Carn Chuinneag and Inchbae

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Abstract
A study of the ortho-gncisses in the Carn Chuinneag-Inchbae complex indicates that the main acid gneisses represent original pre-tectonic orthoclase granites. The earlier basic rocks have recrystallized to amphibolites characterized by a highly aluminous hornblende. The intermediate rocks of the complex are believed to have formed by a process of hybridization. The acid gneisses have been reclassified and mapped as separate divisions. The Lochan a'Chairn subdivision has been recognized. An analysis of the riebeckite from the riebeckite gneissic granite shows it to be similar to riebeckites from Nigeria and to contain more of the arfvedsonite component than riebeckite proper. An examination of the spread of albitization into the surrounding rocks from the garneti-ferous albite gneiss, and an analysis of the garnet, indicate that the emplacement of this gneiss, probably with the magnetite-cassiterite ore bands which are confined to it, took place late in the igneous cycle.

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