40Ar/39Ar laserprobe dating of mylonitic fabrics in a polyorogenic terrane of NW Iberia
The tectonothermal evolution of a polyorogenic terrane in the Variscan belt of NW Spain has been constrained by 40Ar/39Ar laserprobe incremental heating experiments on mylonitic fabrics developed in major structures. Transitional levels between HP–HT and IP upper units in the O´ rdenes Complex where...
| Autores: | , , , , , , |
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| Tipo de documento: | artigo |
| Data de publicação: | 2006 |
| País: | España |
| Recursos: | Universidad Complutense de Madrid (UCM) |
| Repositório: | Docta Complutense |
| Idioma: | inglês |
| OAI Identifier: | oai:docta.ucm.es:20.500.14352/49778 |
| Acesso em linha: | https://hdl.handle.net/20.500.14352/49778 |
| Access Level: | Acceso aberto |
| Palavra-chave: | 552.3 Polyorogenic terrane Variscan belt NW Iberian Petrología |
| Resumo: | The tectonothermal evolution of a polyorogenic terrane in the Variscan belt of NW Spain has been constrained by 40Ar/39Ar laserprobe incremental heating experiments on mylonitic fabrics developed in major structures. Transitional levels between HP–HT and IP upper units in the O´ rdenes Complex where metamorphic 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´s extensional 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 structures related to the Variscan convergence in the area, which include top-to-the-east thrusts and extensional detachments. A single, younger Carboniferous age obtained from the uppermost allochthonous sequences possibly reflects the final stages of emplacement of the allochthonous complexes. Our data indicate a polyorogenic 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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