Post-collisional Permian volcanism in northwestern Corsica: an assessment based on mineralogy and trace-element geochemistry

Abstract

Within the Western Mediterranean Permo-Triassic province, the Scandola-Senino area represents one of the best sites for the study of the successive volcanic episodes and their relationships. With this purpose, new mineralogical and geochemical data on basic and intermediate rocks are presented. The first volcanic episode, including andesites, dacites, and rhyolitic ignimbrites of Early Permian age, is calc-alkaline with a strong LILE enrichment, particularly in K, U and Th. Andesite evolution is controlled by fractional crystallization with an important crustal component. Subsequent permian volcanism corresponds to the emplacement of bimodal volcanic products (basalt-ignimbritic rhyolite) into a caldera structure. The basalts are interpreted as derived from a mantle source still modified by subduction component. The last volcanic episode is represented by doleritic dykes derived from a within plate or OIB-type source devoid of any arc signature (no Ta anomaly). Permian magmatism in Corsica is interpreted as the progressive fading-out of an arc-signature in favour of a primitive mantle source. The magmatic features and the structural setting agree with an inferred post-orogenic geotectonic regime during the period between the Hercynian and Early Alpine orogenic events.