PERMO-CARBONIFEROUS VOLCANISM IN EUROPE AND NORTHWEST AFRICA - A SUPERPLUME EXHAUST VALVE IN THE CENTER OF PANGAEA

The Permo-Carboniferous transition in the European-northwest African p rovince was characterised by widespread volcanism (calc-alkaline with crustal and/or mantle lithospheric characteristics followed by alkalin e/subalkaline with HIMU-type signature) with a maximum in the Stephani an-Autunian (Late Pennsylvannian to Early Permian). Extrusion of volca nics was accompanied by massive S-type synextensional granitic intrusi ons and hydrothermal mineralisation. The geotectonic framework involve d the gravitational collapse of the Variscan Belt by extensional detac hment tectonics, and its final disruption by wrench faulting. The char acteristics of this volcanism are explained within progressively evolv ing extensional processes. It is suggested that this Permo-Carbonifero us Pangaean volcanic province might be interpreted in terms of a super plume impinging on the base of the lithosphere. This model envisages t hat magmatism acted as an exhaust valve releasing the heat accumulated beneath the Pangaean supercontinent by insulation and blanketing proc esses which triggered large-scale mantle-wide upward convection and ge neral instability of the supercontinent. (C) 1998 Elsevier Science Lim ited.