Protracted felsic magmatic activity associated with the opening of the South Atlantic

Felsic magmatism is often observed in the final stages of the eruption of continental large igneous provinces. The occurrence of these felsic extrusive igneous rocks potentially provides key information on the complex interplay of magmatism and tectonics. In this paper we investigate the timing of eruption of Early Cretaceous felsic magmas associated with the Paraná-Etendeka flood basalt province using the ⁴⁰Ar/ ³⁹Ar technique and interpret the results in terms of the recently proposed petrogenetic histories and dominant stress factors. There appears to be a link between lithospheric thinning and a change in the origin of the felsic magmas, from open system fractional crystallization to mid/lower crustal melting, particularly in southern Uruguay.