Glen Garry vein complex

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Abstract
Synopsis: The vein complex is one of several phases of late Caledonian igneous activity NW of the Great Glen. It post-dates the regional suite of microdiorites and the Cluanie Granodiorite. The veins which are massive and cross-cutting are predominantly of granodiorite composition although they range from quartz-diorite to leucogranite. Cross-cutting relationships consistently indicate that the more acid members are the youngest in the intrusive sequence. Major element analysis defines the complex as a chemically coherent suite which is readily distinguishable from other Caledonian calc-alkaline rocks. The complex has evolved by fractional crystallization. Major and minor element analyses as well as textural relationships indicate that the suite was dominated by fractionation of firstly hornblende and then plagioclase. Comparisons of this sequence with published experimental data and consideration of feldspar analyses suggests that the suite may have evolved at relatively high water pressures. The source of the parent quartz-diorite magma is problematical. The Moine host rocks are too silicic and too potassic. Also, trace element chemistry indicates some differences from published analyses of Lewisian basement rocks. Intrusion of the suite may be related to late Caledonian stresses associated with faulting on the Great Glen Fault.