Abstract
Recent work has revealed that the Montagne Noire dome, located in the foreland of the Variscan belt (French Massif Central), contains a record of nearly coeval, late Variscan eclogitization and migmatization. Given these new results, it is important to understand the chronology of events that produced high-grade metamorphism and exhumation. Using U-Th-Pb dating of monazite, this study confirms ages of ~315–300 Ma for high-T metamorphism in the augen gneiss that makes up a large fraction of the Montagne Noire dome, and documents for the first time ~295 Ma monazite ages in compositionally varied fine-grained gneisses that form folded continuous layers within the core of the dome. The fine-grained gneiss layers are intensely sheared and are interpreted to have localized late, high-T deformation in the core of the dome. These sheared fine-grained gneisses form a network of shear zones that were kinematically linked to the extensional and strike-slip deformation zones that exhumed the Montagne Noire dome in a pull-apart (s.l.) domain. Continued deformation-recrystallization and fluid flow within these shear zones likely drove rejuvenation of monazite for ~5 million years after much of the melt had crystallized in the Montagne Noire dome.
| Original language | English (US) |
|---|---|
| Article number | 228316 |
| Journal | Tectonophysics |
| Volume | 776 |
| DOIs | |
| State | Published - Feb 5 2020 |
Bibliographical note
Funding Information:This research was supported by National Science Foundation (US) grant EAR-1050020 to Teyssier and Whitney, including funds from NSF International Programs that helped facilitate international collaboration with scientists at the University of Montpellier. We thank Cyprien Astoury for mineral separation, Jennifer Wright and Roxanne Renedo (University of Minnesota) for early investigation of the FGG, Olivier Raynal for his accurate map and cross section of the Gorges d'Héric, and Maurice Brunel, Philippe Matte, Renaud Caby, André Leyreloup, Mickael Rabin, Pierre Trap, and Bénédicte Cenki-Tok for field trips and discussions in the Montagne Noire. We also thank Philippe Agard, Romain Tartèse, and an anonymous reviewer who helped improve the manuscript.
Funding Information:
This research was supported by National Science Foundation (US) grant EAR-1050020 to Teyssier and Whitney, including funds from NSF International Programs that helped facilitate international collaboration with scientists at the University of Montpellier. We thank Cyprien Astoury for mineral separation, Jennifer Wright and Roxanne Renedo (University of Minnesota) for early investigation of the FGG, Olivier Raynal for his accurate map and cross section of the Gorges d'H?ric, and Maurice Brunel, Philippe Matte, Renaud Caby, Andr? Leyreloup, Mickael Rabin, Pierre Trap, and B?n?dicte Cenki-Tok for field trips and discussions in the Montagne Noire. We also thank Philippe Agard, Romain Tart?se, and an anonymous reviewer who helped improve the manuscript. All the data used in this study are available in the main text and in the Supporting information of this manuscript.
Publisher Copyright:
© 2020 Elsevier B.V.
Keywords
- Exhumation of partially molten crust
- Fine grained gneisses
- High-T deformation
- Migmatite dome
- Monazite U-Th-Pb dating
- Montagne Noire, France