40Ar–39Ar ages and isotope geochemistry of Cretaceous basalts in northern Madagascar: refining eruption ages, extent of crustal contamination and parental magmas in a flood basalt province

40Ar–39Ar ages and isotope geochemistry of Cretaceous basalts in northern Madagascar: refining eruption ages, extent of crustal contamination and parental magmas in a flood basalt province