Rhaetian tectono-magmatic evolution of the Central Atlantic Magmatic Province volcanism in the Betic Cordillera, South Iberia

Abstract

Volcanic rocks of the Zamoranos Formation exposed in the Betic Cordillera of southern Spain reveal Late Triassic CAMP volcanism extending from southwest to southeast of the Iberian massif. Comparison with volcanic rocks from the Upper Triassic of the Algarve region in Portugal enables correlation between these different magmatic provinces based on the striking geochemical similarity. The studied mafic magmatic rocks in the Betic Cordillera reveal three volcanic episodes during the deposition of the Zamoranos Formation with two types of geochemical affinity: alkaline (Group 1) and sub-alkaline (Group 2 and 3). The sub-alkaline rocks resemble the studied Triassic rocks of Portugal and the magmatism described as CAMP on a global scale. In the present study, the identification of alkaline rocks preceding the main CAMP sub-alkaline phase by ca. 15 Ma, is the first evidence of alkaline precursors prior to CAMP magmatism and indicates a change from a prior deeper enriched mantle source to a subsequent, shallower one. The temporal evolution of alkaline magmatism followed by a CAMP-type sub-alkaline magmatism is best explained in a context of initial rifting during Norian-Rhaetian times. It is inferred that rifting gradually developed from west to east in the southern area of Iberia.