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Structural, metamorphic and geochronological insights on the Variscan evolution of the Alpine basement in the Belledonne Massif (France)
- Source :
- Tectonophysics, Tectonophysics, 2018, 726, pp.14-42. ⟨10.1016/j.tecto.2018.01.017⟩, Tectonophysics, Elsevier, 2018, 726, pp.14-42. 〈10.1016/j.tecto.2018.01.017〉, Tectonophysics, Elsevier, 2018, 726, pp.14-42. ⟨10.1016/j.tecto.2018.01.017⟩
- Publication Year :
- 2018
- Publisher :
- HAL CCSD, 2018.
-
Abstract
- International audience; A structural and petrochronological study was carried out in the southern part of the Belledonne crystalline massif. A first tectonometamorphic event, Dx, corresponds to the eastward thrusting of the Chamrousse ophiolitic complex characterized by a low-temperature–moderate-pressure metamorphism reaching 0.535 ± 0.045 GPa and 427.5 ± 17.5 °C. A subsequent D1 deformation is defined by a penetrative S1 foliation that mostly dips toward the west and displays an E–W- to NE–SW-trending mineral and stretching lineation L1. D1 is associated with a top-to-the east shearing and is responsible for the crustal thickening accommodated by the eastward nappe stacking and the emplacement of the Chamrousse ophiolitic complex upon the Rioupéroux-Livet unit. This event is characterized by an amphibolite facies metamorphism (0.58 GPa ± 0.06; 608 ± 14 °C) that attains partial melting at the base of the nappe pile (0.78 ± 0.07 GPa; 680.5 ± 11.5 °C). LA-ICP-MS U-Pb dating of monazite grains from the mica schists of the Rioupéroux-Livet unit constrain the age of D1 to 337 ± 7 Ma. The D2 tectono-metamorphic event is characterized by NE–SW trending, upright to NE-verging synfolial folding. Folding associated with D2 is pervasively developed in all lithotectonic units with the development of a steeply-dipping S2 foliation. In particular, D2 involves the uppermost weakly metamorphosed Taillefer unit. LA-ICP-MS U-Pb dating performed on detrital zircon grains shows that the Taillefer conglomerates was deposited during the Visean. A zircon SIMS U-Pb age of 352 ± 1 Ma from a plagioglase-rich leucocratic sill of the Rioupéroux-Livet unit is interpreted as the age of magmatic emplacement. Our results suggest that the D2 event took place between 330 Ma and 310 Ma. We propose a new interpretation of the tectonometamorphic evolution of the southern part of the Belledonne massif, focusing on the Middle Carboniferous stages of the Variscan orogeny.
- Subjects :
- 010504 meteorology & atmospheric sciences
Geochemistry
Metamorphism
Thermobarometry
010502 geochemistry & geophysics
01 natural sciences
Nappe
Alpine External Crystalline Massifs
Lineation
SIMS and LA-ICP-MS dating
Metamorphic facies
0105 earth and related environmental sciences
Earth-Surface Processes
[SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics
geography
geography.geographical_feature_category
Schist
Orogeny
[ SDU.STU.TE ] Sciences of the Universe [physics]/Earth Sciences/Tectonics
Massif
Variscan Belt
Geophysics
Zircon and monazite dating
Geology
Zircon
Belledonne Massif
Subjects
Details
- Language :
- English
- ISSN :
- 00401951 and 18793266
- Database :
- OpenAIRE
- Journal :
- Tectonophysics, Tectonophysics, 2018, 726, pp.14-42. ⟨10.1016/j.tecto.2018.01.017⟩, Tectonophysics, Elsevier, 2018, 726, pp.14-42. 〈10.1016/j.tecto.2018.01.017〉, Tectonophysics, Elsevier, 2018, 726, pp.14-42. ⟨10.1016/j.tecto.2018.01.017⟩
- Accession number :
- edsair.doi.dedup.....2b2ab07f97a729b2d9d6dacf2ec8ce92