The BGS Lexicon of Named Rock Units — Result Details

Inchard Gneisses

Computer Code: ICGN Preferred Map Code: Oi
Status Code: Full
Age range: Archaean Eon (AR) — Archaean Eon (AR)
Lithological Description: Comprises grey to pink biotite- and locally hornblende-bearing, granodioritic to tonalitic felsic gneisses, with subordinate bodies of gneissose mafic and ultramafic rock. The general grade of metamorphism is amphobilite facies. The gneiss is comonly migmatitic.
Definition of Lower Boundary: Has a sheared contact with the Scourian Gneiss to the southwest. It is unconformably overlain by the Torridonian Group, and in the east, by the Eribol Formation. The unit is aso intruded by the Rubha Ruadh Granite.
Definition of Upper Boundary: Not applicable, but see details under "Lower Boundary".
Thickness: It is probably at least several kilometres thick, and it is thought that it potentially extends down to the Moho; i.e. greater than 5km.
Geographical Limits: Outcrops of the Inchard Gneiss stretch from approximately the Laxford River in the south to Cape Wrath in the north, from the Moine Thrust belt in the east to the coast in the west. Bodies of gneiss, belonging to he Lewisian Complex within the Moine Thrust belt to the north of Loch Stack are also likely to be part of the Inchard Gneiss.
Parent Unit: Lewisian Complex (L)
Previous Name(s): Laxfordian (-2257)
Rhiconich Gneisses (-1609)
Rhiconich Group (-2861)
Laxfordian (In Part Rhiconich Group) [Obsolete Name And Code: See ICGN And RUBR] (LLX)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Loch Inchard, Sutherland. 
Reference(s):
Friend, C R L and Kinny, P D. 2001. A re-appraisal of the Lewisian Gneiss Complex: geochronological evidence for its tectonic assembly from disparate terranes in the Proterozoic. Contributions to Mineralogy and Petrology, Vol.142, 198-218. 
Kinny, P D, Friend, C R L and Friend, J L G. 2005. Proposal for a terrane-based nomenclature for the Lewisian Complex of NW Scotland. Journal of the Geological Society of London, Vol.162, 175-186. 
Sutton, J and Watson, J V. 1951. The pre-Torridonian metamorphic history of the Loch Torridon and Scourie areas in the northwest Highlands, and its bearing on the chronological classification of the Lewisian. Quarterley Journal of the Geological Society of London, Vol.106, 241-307. 
Sheraton, J W, Skinner, A C and Tarney, J. 1973. The geochemistry of the Scourian gneisses of the Assynt district. 31-43 in Park, R G and Tarney, J (eds) The early Precambrian of Scotland and related rocks of Greenland. [Keele: University of Keele.] 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S107 S113 S108 S114