Timing of granite emplacement, crustal flow and gneiss dome formation in the Variscan segment of the Pyrenees

• DOI: 10.1144/sp405.5
• Publication Date: 2014-02-27T03:27:22Z
• Authors: Yoann Denèle; Bernard Laumonier; Jean-Louis Paquette; Philippe Olivier; Gérard Gleizes; Pierre Barbey
• Keywords: 01 natural sciences; 0105 earth and related environmental sciences

AbstractThe Variscan segment of the Pyrenees is well suited to study the timing of crustal-scale deformations as crustal flow and gneiss dome formation. This has been constrained from a synthesis of available structural and geochronological data of intrusive rocks, as well as new zircon U–Pb age determinations via laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). After a stage of moderate thickening by fold–thrust belt development in the upper crust between 323 and 308 Ma, the Variscan segment of the Pyrenees experienced crustal flow atc.306 Ma and then gneiss dome formation atc.304 Ma. Localization of the deformation along reverse-dextral shear zones occurred atc.300 Ma. The Variscan segment of the Pyrenees recorded a high-temperature regime, which allowed crustal flow of the middle crust, but with limited amounts of heat which induced rapid cooling. The development of this enigmatic orogenic segment of the Variscan belt is closely contemporaneous with the formation of the Cantabrian Orocline and could correspond to a lithospheric-scale shear zone that accommodated buckling of the orocline. Late Variscan lithospheric delamination and asthenospheric upwelling associated with buckling in the core of the Cantabrian Orocline could explain the short-period high-temperature regime in the Variscan segment of the Pyrenees.Supplementary material:Review of published U–Th–Pb, Ar–Ar and K–Ar ages of granites from the Axial Zone of the Pyrenees; LA-ICP-MS U–Pb dating methodology (Clermont-Ferrand, France); and zircon LA-ICP-MS U–Pb data for Ax-les-Thermes, Carançà, Mont-Louis and Cauterets granites are available athttp://www.geolsoc.org.uk/SUP18729.