Did the Variscides collapse or were they torn apart?: A quantitative evaluation of the driving forces for postconvergent extension in central Europe

Post-collisional rapid exhumation and erosion during continental sedimentation: the example of the late Variscan Salvan-Dor�naz basin (Western Alps)

“…Clastic sediments filling intra-and perimontane Permo-Carboniferous basins record the tectono-metamorphic and magmatic history at the end of the convergence (Henk 1999). Such basins are suitable for establishing the general tectonic setting as their texture and composition are primarily linked to the source-area geology, depositional environment and climate (e.g., Dickinson 1974;Bhatia and Crook 1986;Ingersoll 1988).…”

40 Ar/ 39 Ar phlogopite geochronology of lamprophyre dykes in Cornwall, UK: new age constraints on Early Permian post-collisional magmatism in the Rhenohercynian Zone, SW England

“…These similarities suggest that the processes responsible for post-collisional magma generation and emplacement in various parts of the orogen are genetically A transition from convergent to extensional/transtensional tectonics during the latest Carboniferous is recorded throughout most of NW Europe (e.g. Arthaud and Matte 1977;Henk 1999;Wilson et al 2004;Ziegler and Dèzes 2006) Extension in SW England is unlikely to be driven by orogenic collapse as there is little evidence for substantial crustal thickening and subsequent exhumation of high-grade metamorphic rocks. Extension of previously-thickened lithosphere due to latest Carboniferous changes in plate boundary stresses is a viable alternative (Henk, 1997;1999) that is broadly synchronous with intraplate extensional and transtensional rift processes operating across the post-Variscan foreland (Wilson et al 2004;Timmermann et al 2009).…”

“…Arthaud and Matte 1977;Henk 1999;Wilson et al 2004;Ziegler and Dèzes 2006) Extension in SW England is unlikely to be driven by orogenic collapse as there is little evidence for substantial crustal thickening and subsequent exhumation of high-grade metamorphic rocks. Extension of previously-thickened lithosphere due to latest Carboniferous changes in plate boundary stresses is a viable alternative (Henk, 1997;1999) that is broadly synchronous with intraplate extensional and transtensional rift processes operating across the post-Variscan foreland (Wilson et al 2004;Timmermann et al 2009). The distinction between changing plate boundary stresses, lithospheric delamination and slab detachment is problematical as all can result in lithospheric thinning, asthenosphere upwelling, partial melting, bimodal magmatism, uplift and extension centered on the suture zone.…”

Syn-convergent high-temperature metamorphism and magmatism in the Variscides: a discussion of potential heat sources

“…Rolet et al (1994) described a syn-collisional metamorphic evolution with progressive pressure decrease and temperature rise from the Armorican Massif (see also Brown & Dallmeyer (1996)) and, similarly, Santallier et al (1994) reported nappe stacking under decreasing pressures from the French Massif Central. For part of the Variscan Internides (Saxo-Thuringian Zone), a combination of petrological data, isotopic ages and thermal modelling (Henk 1995) suggest exhumation rates of several mm a -1 pointing to tectonic denudation as the dominant exhumation mechanism. The local palaeogeography and contemporaneous sedimentation do not support long-term erosion at such rates.…”

“…It should be noted that this discussion concentrates on only the heat sources for synconvergent metamorphism and magmatism. The geodynamic processes during the younger, postconvergent evolution (in Stephanian-Permian time) are not considered here but have been treated quantitatively by Henk (1999).…”