Lower Cambrian magmatism in the SW Iberian sector of the African–Gondwana margin: geochemical and isotopic keys to incipient tectonic switching

Abstract

Aspects of the evolution of the Pan-African–Cadomian arc have been recognized in several European massifs. The Ossa–Morena Complex (SW Iberian Massif) is one of the best-preserved sections of this palaeo-Gondwana margin. In this domain, recent studies suggest that arc magmatism followed a cyclical pattern during the Upper Ediacaran and Lower Cambrian. However, its initial and more mature stages remain unclear. Upper Ediacaran magmatism (c. 602 Ma) appears to be uninterrupted and driven by slab–mantle wedge–upper plate interactions. The early Paleozoic was a period of significant change along the Gondwana margin. In the Ossa–Morena Complex, the beginning of the Cambrian (c. 541 Ma) is marked by a strong unconformity over the Ediacaran basement, which is linked to destabilization of the arc. However, subduction-related magmatism continued with increasing mantle input, driving the geochemistry to more alkaline compositions. This paper summarizes the geochemical and isotopic evolution of the peri-Gondwana arc preserved in SW Iberia during this period. These results highlight shifts in geochemistry related to a higher slab angle during each magmatic episode, suggesting a tectonic switch toward an extensional regime in this section of the Gondwana margin.