Geochronological constraints on the evolution of a suture: the Ossa-Morena/Central Iberian contact (Variscan Belt,south-west Iberian Peninsula) |
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Authors: | Antonio Azor Francisco González Lodeiro J Fernando Simancas Fernando Bea |
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Institution: | (1) Departamento de Geodinámica, Universidad de Granada, Campus de Fuentenueva S/N, E-18002 Granada, Spain;(2) Departamento de Mineralogía y Petrología, Universidad de Granada, Avenida de Fuentenueva S/N, E-18002 Granada, Spain |
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Abstract: | One of the main tectonic boundaries of the Variscan Belt in the Iberian Peninsula is the Ossa-Morena/Central Iberian contact. This contact is marked by a highly deformed unit (Central Unit) which recorded an initial high-pressure/high-temperature metamorphic evolution. Rb-Sr whole-rock isotopic data from three gneissic bodies cropping out in the Central Unit yield two Late Proterozoic ages (690 ± 134 and 632 ± 103 Ma) and an early Palaeozoic age (495 ± 13 Ma), which we interpret as protolith ages. The two Late Proterozoic orthogneisses show initial 87Sr/86Sr ratios typical of mantle-derived materials or those with significant mantle participation (87Sr/86Sr > 0.709). These new radiometric data, together with ages previously published and the structural evolution of the Central Unit, lead to the conclusions that: (1) there are magmatic protoliths of Late Proterozoic and Early Palaeozoic ages; (2) the metamorphic evolution of this area, including the high-pressure event, belongs to the Variscan orogenic cycle; (3) the deformations observed affect the rocks of the entire Central Unit, accordingly they are post-Ordovician, i.e. Variscan; and (4) consequently, the Ossa-Morena/Central Iberian contact is interpreted here as a Variscan suture. |
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Keywords: | IBERIAN Peninsula Variscan suture Rb-Sr whole-rock isotopic data Protolith ages Orthogneisses |
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