%0 Journal Article
%A Gómez Barreiro, Juan
%A Wijbrans, Jan R.
%A Castiñeiras García, Pedro
%A Martínez Catalán, José R.
%A Arenas Martín, Ricardo
%A Díaz García, Florentino
%A Abati Gómez, Jacobo
%T 40Ar/39Ar laserprobe dating of mylonitic fabrics in a polyorogenic terrane ofNW Iberia
%D 2006
%@ 0016-7649
%U https://hdl.handle.net/20.500.14352/49778
%X The tectonothermal evolution of a polyorogenic terrane in the Variscan belt of NW Spain has beenconstrained by 40Ar/39Ar laserprobe incremental heating experiments on mylonitic fabrics developed in majorstructures. Transitional levels between HP–HT and IP upper units in the O´ rdenes Complex wheremetamorphic and structural records demonstrate two cycles of burial and exhumation were selected for dating.Two groups of ages have been defined: (1) Silurian–Early Devonian, obtained from mylonites of the Forna´sextensional detachment, here considered as the minimum age for the start of tectonic exhumation of the HP–HT units and an upper age-limit for the HP–HT event itself; (2) Early to Mid-Devonian, from structuresrelated to the Variscan convergence in the area, which include top-to-the-east thrusts and extensionaldetachments. A single, younger Carboniferous age obtained from the uppermost allochthonous sequencespossibly reflects the final stages of emplacement of the allochthonous complexes. Our data indicate apolyorogenic character for a part of the Iberian allochthonous complexes, including Variscan (sensu stricto)and Early Variscan convergence, as well as an older, Early Palaeozoic cycle.
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