Abstract
Synopsis: Detailed petrochemical work on dolerites from, each of the three centres of Tertiary igneous activity in Ardnamurchan suggests that the (calculated) composition of the initial magmatic liquid giving rise to the Centre 1 dolerites is SiO 2 52.5%, TiO 2 1%, A1 2 O 3 13.5%, total iron 9.5%, MgO 8.5%, CaO 12%, Na 2 O 2% and K 2 O 1%, on a water-free basis. The early dolerites of Ardnamurchan (Centre 1) are relatively richer in SiO 2 , Cu and Ba, and poorer in A1 2 O 3 and Na 2 O than the late dolerites of Centres 2 and 3.