Extent and significance of the Upper Ordovician felsic volcanism in the Pyrenees and Mouthoumet Massifs, SW Europe

Abstract

Abstract New geochronological (U–Pb isotope dilution thermal ionization mass spectrometry), geochemical and isotopic data from Upper Ordovician felsic volcanic rocks recorded in the Pyrenees and Mouthoumet massifs, SW Europe, suggest that this volcanic activity is more widely represented than previously accepted, and allows a better refinement of the age span involved in the Sardic Unconformity. This Sandbian volcanism represents the final pulse of the Sardic tectonothermal event, starting with the Floian–Darriwilian emplacement of voluminous plutonic rocks and the contemporaneous erosion of the uplifted pre–Upper Ordovician basement, and followed by a tholeiitic volcanism contemporaneous with extensional features and the opening of (half-)grabens finally sealed by Hirnantian glaciomarine deposits. The Sardic-related lithospheric extension may be linked to thermal doming originated by a superplume activity that caused, in turn, an extensive crustal melting responsible for the onset of the felsic (calc-alkaline-dominated), Floian–Darriwilian intrusive and Sandbian extrusive magmatism along the northern margin of Gondwana.