Low- P metamorphism following a Barrovian-type evolution. Complex tectonic controls for a common transition, as deduced in the Mondoñedo thrust sheet (NW Iberian Massif)

摘要: The Mondonedo thrust sheet has been studied to investigate the complex dynamic relationships that may be involved in the development of low- and medium-P metamorphic domains. This unit underwent an initial event during initial stages Variscan convergence, related crustal thickening. Subsequently, evolved a low-P baric type of metamorphism, syn-convergence thinning exhumation. Its footwall, cropping out two tectonic windows, registered different evolution, with history from high-T under high geothermal gradient. Several different P–T paths Mondon˜edo its relative autochthon are traced interpreted according the structural evolution area. Following thickening, main extensional shear zones developed. One them occurs hangingwall, whereas other affects footwall unit. Both zones were contemporaneous ductile thrusting inner parts sheet, their activity is viewed as consequence the need for gravitational re-equilibration within orogenic wedge. The most commonly accepted models tectonothermal regions thickened continental crust assume low-P metamorphism essentially late phenomenon, linked late-orogenic activity. In sheet, our conclusions indicate metamorphism also develop this occur at least two cases. denudation allochthonous emplacement, other, extension the footwall advancing sheet. As consequence, show characteristics different units nappe pile.