Abstract
Synopsis Basic minor intrusions show cross-cutting relations to the regionally-developed Lewisian quartzo-feldspathic gneisses and amphibolites north of Loch Laxford. Their emplacement during the Laxfordian episode is indicated by the isotopic date of c. 1900 m.y. for the gneisses which they cut and the later emplacement of pegmatite and the development of crush-rock. Correspondence of chemical composition and mineralogy with other Lewisian basic igneous masses showing longer tectonic and metamorphic histories, together with difficulty of establishing whether concordance is the result of igneous or tectonic activity, makes such rock masses unsuitable for use as stratigraphic time-markers.
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