The BGS Lexicon of Named Rock Units — Result Details

Assynt Meta-Olivine Gabbro Subswarm [Obsolete Name And Code: Use SMOG]

Computer Code: AMOG Preferred Map Code: notEntered
Status Code: Index Level
Age range: Palaeoproterozoic Era (AL) — Palaeoproterozoic Era (AL)
Lithological Description: Comprises the Fe-rich members of the Scourie Dyke Swarm. The dykes of the Subswarm occur within the Lewisian Gneiss Complex in the Assynt region, and they typically have a broadly east-west trend. They have the primary mineralogy olivine - clinopyroxene - orthopyroxene - plagioclase - kaersutite - biotite - Fe-Ti oxide, although most have been subjected to amphibolite-facies metamorphism and thus many of the original minerals have been replaced.
Definition of Lower Boundary: Contacts are cross-cutting, and have been modified by subsequent metamorphism.
Definition of Upper Boundary: N/A.
Thickness: From about 50 cm to 50 m thick.
Geographical Limits: The dykes are part of the Lewisian Gneiss Complex and only occur within it. They have only been mapped as a separate subswarm in the Assynt area (between Loch Laxford in the north and Loch Lurgainn in the south).
Parent Unit: Scourie Dyke Swarm (SCOUR)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  The dykes of the Subswarm occur in the Lewisian Gneiss Complex of Assynt. The most well-studied examples are at Loch Sionascaig [NC 136 145]. Tarney, 1973; Tarney & Weaver, 1987. 
Reference(s):
Tarney, J. and Weaver, B L. 1987. Mineralogy, petrology and geochemistry of the Scourie dykes: petrogenesis and crystallization processes in dykes intruded at depth. p. 217-233 in Evolution of the Lewisian and Comparable Precambrian High Grade Terrains. Park, R.G. and Tarney, J. (eds.) Geological Society Special Publication No. 27. 
Weaver, B L and Tarney, J. 1981. The Scourie Dyke Suite: Petrogenesis and Geotechnical Nature of the Proterozoic Sub-Continental Mantle. Contributions to Mineralogy and Petrology, Vol.78, 175-188. 
Tarney, J. 1973. The Scourie Dyke Suite and the nature of the Inverian event in Assynt. 105-117 in Park, R G and Tarney, J (editors), The Early Precambrian of Scotland and related rocks of Greenland. [University of Keele.] 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S101 S102 S107 S108