Tectonism and vulcanicity of the Permocarboniferous Basin and Range Province of Western Europe.

Abstract

During the Carboniferousdic elongatedSouth EuropePlate was bounded by two fold beltswhich migratedaway from a centralcontinentalridge, pointing to two subductionzonesalong the NW and SE ma¿rginsof South Europe retreatingocean-wards.Due to releaseof abondantwater during subduetion, dehydrationand probablepartial melting of former oceaniccrust at the two subductionzones,one or severalupper mantle diapirs formed. Ríse of this hot upper mantle material causedwidespreadpartial melting in the lower crust of SouthEuropeandhigh temperature-lowpressuremetamorphism,and is believed to have reducedthe thickness and rigidity of the South Europe Plate considerably. Subductionof the Mid-Europeanoceancrust northwestof South Europe finally lcd to collision with North America-Europeand subduction of the Tethys oceancrust lcd to collision of South Europewith Africa in the southwest. Both collisions terminatedthe orogenicactivity at the sites of the fold bites. Approaching North Amcrica-EuropeandAfrica, South Europecollided with the irregulary rifted continental margins of the two adjacent plates. Enabledto do so by its reducedrigidity the South Europe Plate consequently deformed in orderto fit the irregularitiesof the adjacentcontinentalmargins. The originally presumablecollinearstructuresof South Europewere distorted and through rotations and translationsa number of subplatesformed separated from cach other by major wrench faults. The late Hercyniangeodynamic history of the various subplatesdevelopedalong similar paths. The hot uppcr mantle diapir causedregional uplift of the crust of South Europe,retreal of the seaand extensiveerosion.In additionlateral spreading of the diapir lcd lo regional crustal extensionand formation of intermontane graben-likebasins.Crustal spreadingwas initiated in the central continental ridge in uppermostVisean time xvhile simultaneouslyin the northwest and southeastcompressivestressregimeswere maintainedbecauseof the continued activity of the subductionzones. Shortly afterwards the firsí basaltic