TY - JOUR
T1 - Timing of formation and exhumation of the montagne noire double dome, french massif central
AU - Roger, Françoise
AU - Teyssier, Christian
AU - Respaut, Jean Patrick
AU - Rey, Patrice F.
AU - Jolivet, Marc
AU - Whitney, Donna L.
AU - Paquette, Jean Louis
AU - Brunel, Maurice
N1 - Publisher Copyright:
© 2014 Elsevier B.V.
PY - 2015/1/20
Y1 - 2015/1/20
N2 - New U-Pb monazite, zircon, and xenotime ages date the Late Carboniferous crystallization of the anatectic Vialais granite in the Montagne Noire Axial Zone and the high-temperature deformation and metamorphism of the augen gneiss (Ordovician granite protolith) from which the granite was likely derived. The U-Pb monazite ages obtained from the augen gneiss (308. ±. 3. Ma), late kinematic Vialais granite (303. ±. 4. Ma), and post-kinematic leucogranite (298. ±. 2. Ma), bracket the high-temperature deformation and metamorphism at ~. 310-300. Ma, clearly postdating regional contraction and nappe emplacement (>. 320. Ma). The planar-linear and locally linear fabrics in the augen gneiss outline a regional-scale double dome structure (Caroux and Espinouse sub-domes) containing smaller (km-scale) upright folds. Compared to the Caroux sub-dome, the larger, migmatitic Espinouse sub-dome contains abundant leucosome, leucogranite bodies and late-kinematic intrusions (Vialais granite). The Vialais granite displays a weak magmatic foliation that defines the main layering of the Espinouse migmatite. Ellipsoidal quartz-sillimanite nodules concentrated above the roof of the granite recorded an increment of strain (vertical shortening, E-NE elongation) during granite emplacement and crystallization, consistent with the extension event that exhumed the domes. These new geochronological and structural data suggest that the Montagne Noire double dome formed in a pull-apart structure within a dextral strike-slip system. Upright folding in the sub-domes has been traditionally assigned to a regional contraction event; alternatively, we propose that local contraction is associated with the convergence of low-viscosity crust beneath the upper crust pull-apart. Dynamic models of extension of hot crust indicate that contraction at depth is generated by flow of low-viscosity orogenic crust converging and rising to fill the gap created by upper crust extension. This interpretation solves the long-standing problem of apparent coeval contraction and extension in the Montagne Noire double dome and establishes migmatite dome emplacement in strike-slip corridors as a style of late Variscan tectonics.
AB - New U-Pb monazite, zircon, and xenotime ages date the Late Carboniferous crystallization of the anatectic Vialais granite in the Montagne Noire Axial Zone and the high-temperature deformation and metamorphism of the augen gneiss (Ordovician granite protolith) from which the granite was likely derived. The U-Pb monazite ages obtained from the augen gneiss (308. ±. 3. Ma), late kinematic Vialais granite (303. ±. 4. Ma), and post-kinematic leucogranite (298. ±. 2. Ma), bracket the high-temperature deformation and metamorphism at ~. 310-300. Ma, clearly postdating regional contraction and nappe emplacement (>. 320. Ma). The planar-linear and locally linear fabrics in the augen gneiss outline a regional-scale double dome structure (Caroux and Espinouse sub-domes) containing smaller (km-scale) upright folds. Compared to the Caroux sub-dome, the larger, migmatitic Espinouse sub-dome contains abundant leucosome, leucogranite bodies and late-kinematic intrusions (Vialais granite). The Vialais granite displays a weak magmatic foliation that defines the main layering of the Espinouse migmatite. Ellipsoidal quartz-sillimanite nodules concentrated above the roof of the granite recorded an increment of strain (vertical shortening, E-NE elongation) during granite emplacement and crystallization, consistent with the extension event that exhumed the domes. These new geochronological and structural data suggest that the Montagne Noire double dome formed in a pull-apart structure within a dextral strike-slip system. Upright folding in the sub-domes has been traditionally assigned to a regional contraction event; alternatively, we propose that local contraction is associated with the convergence of low-viscosity crust beneath the upper crust pull-apart. Dynamic models of extension of hot crust indicate that contraction at depth is generated by flow of low-viscosity orogenic crust converging and rising to fill the gap created by upper crust extension. This interpretation solves the long-standing problem of apparent coeval contraction and extension in the Montagne Noire double dome and establishes migmatite dome emplacement in strike-slip corridors as a style of late Variscan tectonics.
KW - Extensional tectonics
KW - Gneiss dome
KW - ID-TIMS and LA-ICP-MS U/Pb dating
KW - Late carboniferous crustal flow
KW - Partial melting
KW - Variscan belt
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U2 - 10.1016/j.tecto.2014.12.002
DO - 10.1016/j.tecto.2014.12.002
M3 - Article
AN - SCOPUS:84921988956
SN - 0040-1951
VL - 640
SP - 53
EP - 69
JO - Tectonophysics
JF - Tectonophysics
ER -