%0 Journal Article
%A Arenas Martín, Ricardo
%A Martínez Catalán, José Ramón
%T Low-P metamorphism following a Barrovian-type evolution.Complex tectonic controls for a common transition, as deducedin the Mondon˜edo thrust sheet (NW Iberian Massif)
%D 2003
%@ 0040-1951
%U https://hdl.handle.net/20.500.14352/50224
%X The Mondoñedo thrust sheet has been studied to investigate the complex dynamic relationships that may be involved in thedevelopment of low- and medium-P metamorphic domains. This unit underwent an initial medium-P event during the initialstages of Variscan convergence, related to crustal thickening. Subsequently, the thrust sheet evolved to a low-P baric type ofmetamorphism, related to syn-convergence thinning and exhumation. Its footwall, cropping out in two tectonic windows,registered a different evolution, with a low-P history that evolved from low- to high-T under a high geothermal gradient. Severaldifferent P–T paths of the Mondon˜edo thrust sheet and its relative autochthon are traced and interpreted according to thestructural evolution of the area. Following the initial crustal thickening, two main syn-convergence extensional shear zonesdeveloped. One of them occurs in the hangingwall, whereas the other affects the footwall unit. Both extensional shear zones werecontemporaneous with ductile thrusting in the inner parts of the thrust sheet, and their activity is viewed as a consequence of theneed for gravitational re-equilibration within the orogenic wedge.The most commonly accepted models of tectonothermal evolution in regions of thickened continental crust assume that low-Pmetamorphism is essentially a late phenomenon, and is linked to late-orogenic tectonic activity. In the Mondon˜edo thrust sheet,our conclusions indicate that low-P metamorphism may also develop during convergence, and that this may occur in at least twocases. One is tectonic denudation of an allochthonous unit during its emplacement, and the other, thinning and extension at thefootwall unit of an advancing thrust sheet. As a consequence, the low-P evolution may show different characteristics in differentunits of an orogenic nappe pile.
%~