The late Proterozoic Curaca mafic dyke swarm is one of the more alkaline swarms of the Brazilian Precambrian. Intra-dyke chemical variations are characterised by higher abundances of incompatible elements in dyke margins than in the dyke centres, a feature that may have resulted from flowage differentiation, from progressive evacuation of liquids from zoned magma chambers, or possibly through dynamic melting of an uprising diapir. Inter-dyke chemical differences are best interpreted by different extents of melting of a mantle source with a small modal proportion of garnet. This source was heterogeneous and had the trace element compositions of ocean island basalts with Dupal and non-Dupal characteristics. The emplacement of the Curaca dykes from 650-700 Ma may have been facilitated by the extensional tectonics perpendicular to the collision zone between the Sao Francisco craton and the Pernambuco-Alagoas massif during the evolution of the Sergipano orogen. The energy in the system was insufficient to promote much melting of, or interaction with, the continental lithosphere or overlying crust.53416992748