Evolución tectonotermal de paragneises de alta-P y alta-T (sutura Varisca, NO del Macizo Ibérico)
- I. Novo-Fernández 1
- R. Arenas 1
- A. Garcia-Casco 2
- R. Díez Fernández 1
- R. Albert 3
- S. Sánchez Martínez 1
- A. Gerdes 3
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1
Universidad Complutense de Madrid
info
- 2 Univ. de Granada
- 3 Goethe-Universität
ISSN: 1576-5172
Any de publicació: 2021
Títol de l'exemplar: X Congreso Geológico de España
Número: 18
Pàgines: 1056
Tipus: Article
Altres publicacions en: Geotemas (Madrid)
Resum
The NW of the Iberian Massif is characterized by the presence of several allochthonous complexes that delineate a Variscan suture zone. The Upper Units crop out at top of the complexes and represent the remnants of a Cambrian peri-Gondwanan magmatic arc. They underwent an Early Devonian (c. 389 Ma, U-Pb on zircon) HP-HT metamorphic event during the con- vergence of Gondwana and Laurussia that assembled Pangea. In the Órdenes Complex, the Sobrado Unit is constituted by ultramafic rocks, eclogites, granulites and HP migmatitic paragneisses. The latter are composed of garnet + kyanite + bio- tite + plagioclase + K-feldspar + quartz + rutile + ilmenite + melt. Thermodynamic modelling of the residual composition reveals metamorphic peak conditions at 15 kbar and 825ºC. The prograde P-T path has been assessed by means of a melt-re- integration method. To do so, an appropriate composition of liquid in equilibrium with the residuum has been calculated to emulate the pre-melting composition of the rock. Thermodynamic modelling of this composition reveals the existence of an initial and colder high-P event. The geodynamic evolution proposed includes subduction to great depth of the rocks, where they were heated and then underwent almost isothermal decompression.