The Uplift of Armorica and the Bretonian Movements of the Variscan Orogeny-New Insights From Detrital Zircons in the Early Carboniferous Terrigenous Rocks of the Laval Basin (Armorican Massif, France)
Résumé
In the French Armorican Massif, the Bretonian phase of the Variscan orogeny has been defined by the Late Devonian (Famennian-Frasnian) erosion gap, and the Early Carboniferous (Tournaisian) syntectonic terrigenous deposits of the l'Huisserie formation in the Laval basin in the Central-North Armorican Domain, ascribed to the Armorica microcontinent. This phase is coeval with vertical (epeirogenic) movements. In addition to Neo-, and Paleo-Proterozoic peaks, ascribed to the Cadomian and Icartian events, respectively, the detrital zircon age populations of the l'Huisserie formation reveal the existence of a 388-358 Ma magmatic event previously recognized by the ca 367-360 Ma dolerite dyke swarms exposed in the N. part of the Central-North Armorican Domain. The isotopic (εHf) signature of these grains documents a pre-orogenic Variscan mantle contribution for the mafic magmatism interpreted here as the indication of the south-directed subduction of the Le Conquet-Teplá ocean, that is, a branch of the Rheic ocean, below the Armorica microcontinent during the Bretonian phase. The intraplate opening of the Laval, Ménez-Bélair, and Châteaulin basins was coeval with this subduction. In the Laval area, the final closure of the basin, accommodated by north-directed folds-andthrusts, took place after the Bashkirian (ca 320 Ma).
Mots clés
- Geosystems
- Geophysics
- 18FR95A Siltstone l'Huisserie formation Tournaisian 48°01′34.68″N 00°45′07.45″W 18FR95B Coarse grain sandstone l'Huisserie formation Tournaisian 48°01′34.68″N 00°45′07.45″W 18FR95C Black siltstone l'Huisserie formation Tournaisian 48°01′34.68″N 00°45′07.45″W 18FR96 Quartz-rich white sandstone l'Huisserie formation Tournaisian 48°00′58.35″N 00°42′15.10″W 18FR97 Quartz-rich sandstone l'Huisserie formation Tournaisian 48°00′00.93″N 00°40′38.19″W 18FR101 Massive white sandstone l'Huisserie formation Tournaisian 47°51′33.55″N 00°26′16.29″W Geochemistry
- 18FR95A Siltstone l'Huisserie formation Tournaisian 48°01′34.68″N 00°45′07.45″W 18FR95B Coarse grain sandstone l'Huisserie formation Tournaisian 48°01′34.68″N 00°45′07.45″W 18FR95C Black siltstone l'Huisserie formation Tournaisian 48°01′34.68″N 00°45′07.45″W 18FR96 Quartz-rich white sandstone l'Huisserie formation Tournaisian 48°00′58.35″N 00°42′15.10″W 18FR97 Quartz-rich sandstone l'Huisserie formation Tournaisian 48°00′00.93″N 00°40′38.19″W 18FR101 Massive white sandstone l'Huisserie formation Tournaisian 47°51′33.55″N 00°26′16.29″W Geochemistry Geophysics Geosystems
Domaines
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Cite 10.6084/m9.figshare.27157722 Jeu de données Lin, W., FAURE, M., & Meng, L. (2024). Supplemental Material: detrital zircon U-Pb ages and Lu-Hf isotopes in the early Carboniferous terrigenous rocks of the Laval basin (Armorican Massif, France) [Data set]. figshare. https://doi.org/10.6084/M9.FIGSHARE.27157722
