II.—The Moinian and Dalradian Rocks between Glen Roy and the Monadhliath Mountains, Inverness-shire

Abstract

SynopsisThe paper provides the first detailed geological description of a portion of the Grampian Highlands between Glen Roy in the west and the Monadhliath Mountains in the east. Moinian metasediments comprising thick granulites (Eilde Flags = Central Highland Psammitic Group) followed by a variable series of pelites and impersistent quartzites (Monadhliath Schists = Transition Group) are succeeded by Dalradian Limestone (Kinlochlaggan or Ballachulish Limestone = Basal Calcareous Group). The Monadhliath Schists are shown to be stratigraphically equivalent to those of Lochaber below the Ballachulish Limestone.Structurally the area consists of north-easterly anticlines and synclines which are generally isoclinal and often overturned. Many formational junctions are clearly stratigraphical, but the point is discussed whether tectonic contacts (slides) may also be present. Most of the metasediments are of garnet grade, but in the east there is a poorly-developed kyanite zone, and a well-developed sillimanite zone. The high-grade zones are related to a major migmatite and pegmatite belt (the Strathspey Complex); another pegmatite belt occurs farther west around Loch Laggan. Post-tectonic granite, quartz-diorite, diorite and appinite intrusions are also present. The district is traversed by several important north-easterly faults which are later than both the metasediments and the intrusions.