Tectonics and geothermal gradients from subduction to collision in the NW Variscan Iberian Massif

The earliest tectonometamorphic record of tectonic slices incorporated to the base of an orogen holds the key to understand how an orogen is built. The tectonic pile of the NW Iberian section of the Variscan Orogen includes tectonic slices separated by crustal-scale thrusts. The earliest tectonometa...

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Bibliographic Details
Published in:International geology review 2024-01, Vol.66 (1), p.380-404
Main Authors: Rubio Pascual, Francisco J., Martín Parra, Luis M., Díez Fernández, Rubén, Valverde-Vaquero, Pablo, Díez-Montes, Alejandro, Hacar Rodríguez, Manuel P., Iglesias, Justo, Gallastegui, Gloria, Rodríguez Fernández, L. Roberto, Beranoaguirre, Aratz
Format: Article
Language:English
Subjects:
Accretion
continental collision
Crustal accretion
Deposition
Geochronology
Geochronometry
Geothermal gradient
Gradients
Massifs
Mathematical analysis
Monazite
NW Iberian Massif
Orogeny
Recrystallization
Subduction
Subduction (geology)
Subduction zones
Tectonics
Temperature gradients
thermal gradient
U-Pb monazite geochronology
Variscan Orogeny
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Summary:The earliest tectonometamorphic record of tectonic slices incorporated to the base of an orogen holds the key to understand how an orogen is built. The tectonic pile of the NW Iberian section of the Variscan Orogen includes tectonic slices separated by crustal-scale thrusts. The earliest tectonometamorphic record in the uppermost parautochthon is calculated at 11-14 kbar and 450-500°C (P-T gradient about 13°C/km), suggesting a subduction-related metamorphic recrystallization at lower pressure than the overlying Lower Allochthon. Early conditions calculated in the autochthon (9-10 kbar and 425-450°C; 16°C/km) point to a relatively 'cold' collisional setting. Higher thermal gradients obtained from some sections of the autochthon (11-12 kbar and 700-725°C; 21°C/km) and the Lower Parautochthon (7.5 kbar and 550-700°C; 24-31°C/km), correspond to more advanced and 'hot' stages of collision. New U-Pb monazite geochronology indicates a 318-311 Ma age for the final formation of HT domes in the region. We propose the rapid decrease in P-T gradient (from
ISSN:0020-6814
1938-2839
DOI:10.1080/00206814.2022.2073569