The geochemistry of the Devonian lavas of northern Lorne

SUMMARY. Chemical nalyses of the Lorne volcanic rocks show that the basalts and andesites are a closely related suite of lavas, notably rich in alkalis, especially potassium. The rhyolites of the Lorne area do not appear to form a continuous series with the more basic rocks. The various lava types are compared with the plutonic rocks of the area, and a relationship s suggested between the basic lavas and appinitic intrusions. The acid lavas are not comparable togranites inthe area. The late orogenic gneous activity in this part of the Caledonides therefore appears to involve three generations of magma, produced separately but within a short ime of one another. The assumption that all the late Caledonian igneous rocks of the Scottish Highlands are differentiates of a common parent magma isnot justified. THE DEVONIAN lavas of the west of Scotland are an example of the volcanic associa-tion described by Turner and Verhoogen (I96O) as the basalt-andesite-rhyolite association of orogenic regions. They show a close temporal and spatial relationship to a wide variety of acid and basic, plutonic and hypabyssal igneous rocks, all of which were produced uring the latest stages of the Caledonian orogeny. The purpose of this study was to ascertain from chemical evidence whether the Caledonian igneous rock