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Long-term thermo-tectonic evolution of the Montes de Toledo area\ud (Central Hercynian Belt, Spain): constraints from apatite fission-track\ud analysis

By Luis C. Barbero González, U. A. Glasmacher, Carlos Villaseca González, José Ángel López García and Cristina Martín Romera


Abstract In the Montes de Toledo area, located in the\ud axial part of the Central Hercynian zone, a long-term\ud thermo-tectonic evolution can be deduced from apatite\ud fission-track (AFT) data in conjunction with tight geological\ud constraints derived from the knowledge of regional\ud geology and other independent chronometers.\ud The area is composed of two different blocks separated\ud by the Toledo Shear Zone (TSZ). The northern block is\ud a granulite facies anatectic terrane. The southern block\ud is composed of greenschist facies Paleozoic sediments\ud intruded by a late Hercynian granitic pluton. A total of\ud 13 samples have been recovered for AFT analysis. AFT\ud ages in both blocks cluster around 189–221 Ma, with\ud mean confined track lengths between 11.4 lm and\ud 12.4 lm. Modeling of the AFT data indicates that the\ud thermal history is broadly similar in both blocks, which\ud constrains the main movement of the TSZ, as essentially\ud before the Upper Permian. AFT ages in the TSZ cluster\ud around 124–164 Ma, and the track lengths vary between\ud 11.4 lm and 12.4 lm. These data reveal that the fault\ud must have been affected by a later thermal overprint as\ud AFT ages are significantly younger than those of the\ud footwall and hangingwall blocks. This differential thermal\ud resetting is likely related to the advection of localized\ud hydrothermal fluids that are responsible for the\ud widespread Pb–Zn mineralization along the TSZ. These\ud results give an example of resetting AFT data by\ud hydrothermal events. The long-term evolution suggests a\ud lack of important Alpine tectonism in the Montes de\ud Toledo block, in clear contrast to other nearby Hercynian\ud areas such as the Sierra de Guadarrama, where the\ud important effect of Alpine tectonism has almost totally\ud erased the previous thermal signal in the AFT system

Topics: Petrología, Geodinámica
Publisher: Springer Science Business Media
Year: 2005
DOI identifier: 10.1007/s00531-004-0455-y
OAI identifier: oai:www.ucm.es:12305
Provided by: EPrints Complutense

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