The BGS Lexicon of Named Rock Units — Result Details

Assynt Metapicrite Subswarm [Obsolete Name And Code: Use BMP]

Computer Code: AMP Preferred Map Code: notEntered
Status Code: Index Level
Age range: Palaeoproterozoic Era (AL) — Palaeoproterozoic Era (AL)
Lithological Description: Comprises the Mg-rich members of the Scourie Dyke Swarm. The dykes of the Subswarm are most abundant within the Lewisian Gneiss Complex in the Assynt region, and they typically have a broadly east-west trend.The dykes of the Subswarm are picritic and have the primary mineralogy olivine - orthopyroxene - clinopyroxene - plagioclase - phlogopite - chromite, although most have undergone amphibolite-facies metamorphism with replacement of the majority of the primary minerals.
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: As part of the Lewisian Gneiss Complex, the dykes 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  Occur in the Lewisian Gneiss Complex of Assynt, of which the most well-studied examples are at Lochs Beannach [NC 145 264], and Leothaid [NC 144 227]. 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. 
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.] 
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. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S101 S102 S107 S108