Keele Research Repository

Detailed mapping of 120 sq.km, has been carried out within the Moine rocks of the Loch Eil area, West Inverpess-shire. The meta- sedimentary rocks of the Loch Eil Division Moine are composed of a series of psammites, quartzites and 'banded' units with minor semi- pelites. This sequence has been lithologically subdivided into ten lithostratigraphic units. Sedimentological analysis suggests that the metasediments accumulated in a shallow-marine environment.
The Loch Eil Division has been subjected to five phases of deformation (D1-D5). Minor recumbent folding and tectonic sliding occurred during Dl, and resulted in the interleaving of the Loch Eil Division rocks with gneissose lithologies of the underlying Glenfinnan Division Moine. Major folding occurred during D2-D4, and brittle faulting and thrusting during D5.
Amphibolite facies metamorphism (Ml) accompanied Dl: grade was of upper to mid-amphibolite facies in the W of the Loch Eil area and declined eastwards to mid- to low amphibolite facies. Subsequent metamorphic events (M2-M4) only involved the recrystallisation and local retrogression of Ml assemblages during metamorphism of amphibolite and greenschist facies.
The Loch Eil Division lies in tectonic contact with the underlying Glenfinnan Division which, in the Loch Eil area, is composed mainly of migmatitic semi-pelitic gneiss. Structural observations along the E margin of the Glenfinnan Division suggest that it possesses an earlier structural history than that which is apparent in the Loch Eil Division.
The granitic gneisses and amphibolites of the Loch Eil area are considered to be meta-igneous bodies emplaced at an early stage in the tectono-metamorphic history outlined above.