The contact between the Ossa Morena and the South Portuguese zones. Characteristics and significance of the Aracena metamorphic belt, in its central sector between Aroche and Aracena (Huelva)
The boundary between the Ossa Morena and the South Portuguese zones is outlined by the Aracena metamorphic belt. The main characteristics of this region of the Iberian Massif are divided into lithologic, structural, metamorphic, magmatic, geochemical, isotopic and experimental points of view and pre...
| Autores: | , , , , |
|---|---|
| Tipo de recurso: | artículo |
| Fecha de publicación: | 2004 |
| País: | España |
| Institución: | Universidad de Huelva (UHU) |
| Repositorio: | Arias Montano. Repositorio Institucional de la Universidad de Huelva |
| Idioma: | inglés |
| OAI Identifier: | oai:ariasmontano.uhu.es:10272/15542 |
| Acceso en línea: | http://hdl.handle.net/10272/15542 |
| Access Level: | acceso abierto |
| Palabra clave: | Iberian Massif Aracena metamorphic belt Shear deformation HT/LP metamorphism Boninitic affinities Triple junction Macizo Ibérico Banda metamórfica de Aracena Deformación por cizalla Metamorfismo de AT/BP Afinidad boninítica Unión triple |
| Sumario: | The boundary between the Ossa Morena and the South Portuguese zones is outlined by the Aracena metamorphic belt. The main characteristics of this region of the Iberian Massif are divided into lithologic, structural, metamorphic, magmatic, geochemical, isotopic and experimental points of view and presented in this paper. The Aracena metamorphic belt is divided into two main domains: the oceanic domain is composed of MORB-derived metabasites (the Acebuches metabasites) and a former accretionary prism. The continental domain comprises aluminous gneisses and migmatites, calc-silicate rocks, leucocratic gneisses, marbles, amphibolites, syn- to post-tectonic noritic intrusions with high-Mg andesite (boninitic affinities) composition, as well as post tectonic acid-to-basic intrusive rocks. The Acebuches metabasites were firstly affected by a high-temperature/low-pressure event, which currently shows an inverted metamorphic gradient, and is related to SW verging thrusting. The thermal peak related to this metamorphic event displays an age gradient in such a way that older ages have been obtained towards the west. The lower half of the Acebuches metabasite pile was later affected by a mylonitic deformation and a retrometamorphism related to the Southern Iberian Shear Zone. Four ductile deformation phases have been defined in the continental domain: CD-D1 was related to the formation of km-scale recumbent folds. CD-D2 could be associated with an extensional collapse or a gravity spreading, and is coeval with a high-temperature/low-pressure metamorphic event that affected the continental domain and gave place to several migmatitic complexes. CD-D3 produced symmetric upright folds and CD-D4 generated south-verging thrusts and thrusts accommodation folds. The main characteristics of the Aracena metamorphic belt are interpreted as the result of a trench-trench-ridge triple junction evolution. According to the proposed model, the oceanic ridge-trench interaction led to the formation of a slab-free window beneath the continental margin, which provoked the upwelling of the underlying astenosphere and a subsequent thermal rebound. This triple junction migrated along the continental margin towards the east, which gave place to the generation of a high-temperature/low-pressure metamorphic belt in the contact between the Ossa Morena and the South Portuguese zones. |
|---|