Constraints on duration, age and migration of the feeder systems of the Madagascan flood basalt province from high-precision 40Ar/39Ar chronology

The Late Cretaceous magmatism in Madagascar is correlated with the break-up between Madagascar and Greater India, with a presumed track of a hotspot from Madagascar towards the Marion Island. The lava succession and associated dike swarms and sills of western Madagascar (Mailaka area) represent a volumetrically important area of the igneous province. Using plagioclase separates, we obtained two plateau 40 Ar/ 39 Ar ages, and an inverse isochron age ranging from 91.2  ± 1.3 to 92.9  ± 3.8 Ma (2σ). These ages are close to the Cenomanian–Turonian (C–T; 93.9  ± 0.2 Ma) boundary and are indistinguishable from the U–Pb ages available for the capping rhyodacitic unit of the Mailaka lava succession. A filtered compilation of eight ages for northern and central-western Madagascar rocks suggests a duration of the magmatic activity in this part of province in the order of c.3 Ma. If the western Madagascar magmatism is plume-related, the Marion plume would be better located near the Mailaka area at c.93 Ma. The geochemistry of the mafic lavas and dykes of western Madagascar is barely distinguishable from MORB, with an increasing crustal contamination towards the evolved rocks, and does not constrain input of typical components derived by plume magmatism.