The tectonic evolution of the the Lewisian Complex in northern Lewis, Outer Hebrides

The earliest tectonic and metamorphic events recorded in northern Lewis, perhaps of early Scourian (c. 2800 Ma.) age, led to the formation of a gneiss complex in which large areas of banded quartzofeldspathic gneisses were interleaved with narrow belts incorporating metamorphosed supracrustal and intrusive igneous rock. The later (late Scourian and Laxfordian) stages of tectonic evolution were controlled by the development of a north-westerly and a north-easterly lineament which are followed by the present coastlines. The bulk strains recorded in these lineaments are high relative to those in the block which lies between them and a wide concentric zoning is recorded by both structural and metamorphic features. Contrasts between the style and orientation of structures in the lineaments and those of the intervening block appear to have been established at an early stage and enhanced during successive phases. Both fold-structures and fabrics appear to have undergone progressive changes and to be adjusted to the bulk strain rather than to particular strain increments