Extensional Flow during Gravitational Collapse: A Tool for Setting Plate Convergence (Padrón Migmatitic Dome, Variscan Belt, NW Iberia)
Plate convergence analysis in collisional orogens is usually based on the study of major contractional structures and strike-slip shear zones. Here we show how the structural analysis of extensional structures may report the regional or far stress field during relatively local, gravity-driven extens...
| Authors: | , , , |
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| Format: | article |
| Publication Date: | 2012 |
| Country: | España |
| Institution: | Consejo Superior de Investigaciones Científicas (CSIC) |
| Repository: | DIGITAL.CSIC. Repositorio Institucional del CSIC |
| OAI Identifier: | oai:digital.csic.es:10261/75837 |
| Online Access: | http://hdl.handle.net/10261/75837 |
| Access Level: | Open access |
| Keyword: | Metamorphic core complexes Unit ordenes complex Late-orogenic collapse Gneiss domes Tectonic evolution Continental crust Tibetan plateau Geodynamic evolution Northern Gondwana Nortwest Iberia |
| Summary: | Plate convergence analysis in collisional orogens is usually based on the study of major contractional structures and strike-slip shear zones. Here we show how the structural analysis of extensional structures may report the regional or far stress field during relatively local, gravity-driven extensional collapse of a thickened continental crust and how this information may be used to constrain the broad vectors of plate convergence at that time. The Padrón migmatitic dome is a synconvergent extensional system developed in the axial zone of the Variscan belt exposed in the NW part of the Iberian Massif of Spain. This system affected the allochthonous and autochthonous sequences involved in Pangaea’s assembly in Southern Europe. It includes three major extensional shear zones, which have been analyzed in detail to provide a wide ground data set for the discussion of the proposed model. The tectonic flow in the Padrón migmatitic dome and in other coeval structures is characterized by vectors ranging from parallel to oblique, in the latter case with a counterclockwise azimuth in relation to the trend of the orogenic belt. Our model suggests that the extensional collapse of the Variscan belt in NW Iberia would have developed if the convergence between Gondwana and Laurussia had not stopped and that it would have included a dextral component. |
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