Petrography and mineral chemistry as indicators of variations of crystallization conditions in the Loch Lomond and Appin appinite suites, western Scotland

Petrography together with rock and mineral chemistry of the appinite suite and associated lamprophyres in the Loch Lomond district of western Scotland assist in elucidating the nature of the parent magma and the evolutionary history of the rock types, and provide a basis for comparison with the appinite suite in its type locality (Appin district), also in the Scottish Caledonides. In both suites there are intrusions that are pipe-like and emplaced into subvolcanic pipes of explosion-breccia formed when structural traps were breached following the build up of gas pressure during magmatic crystallization. The Loch Lomond suite crystallized from a magma that was calc-alkaline, but with less alkalinity than the magma from which the Appin suite developed. The Ca contents of the clinopyroxenes in it are lower, Ca-rich plagioclase appeared earlier in its crystallization history and the gas pressure (PH2O