Deformation ductile extensive d'age namuro-westphalien dans le plateau d'Aigurande, Massif central francais

Faure, Michel; Prost, A. E.; Lasne, E.

doi:10.2113/gssgfbull.vi.1.189

Cited by 26 publications

(17 citation statements)

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“…The Brâme syntectonic leucogranites in the Limousin [ Mollier and Bouchez , 1982; Faure and Pons , 1991; Faure et al , 1990], emplaced at 324 ± 4 Ma (U‐Pb on zircon [ Holliger et al , 1986]), may share some similarities with the leucogranites of the Velay dome. According to Scaillet et al [1996a], these leucogranites record a progressive exhumation along N‐S normal faults such as Nantiat fault to the west and BMF to the east (Figure 1), with cooling ages varying between 301 Ma at the base, 305 Ma in the center and 314 Ma at the top of the pluton.…”

Section: Discussion In the Scope Of The Geology Of The French Massif mentioning

confidence: 99%

“…Postcollisional intracontinental tectonothermal events extended over a time span of 100 Myr, between 380 and 280 Ma [ Matte , 1991]. The Limousin area, in the northwest part of the Massif Central (France), first experienced crustal shortening and thickening [ Matte , 1986], followed by extension and crustal thinning [ Van den Driesche and Brun , 1989; Faure et al , 1990; Burg et al , 1990; Faure , 1995]. It is characterized by voluminous two‐mica leucogranites resulting from partial melting of the Variscan crustal basement [e.g., Cuney et al , 1990].…”

Section: Introductionmentioning

confidence: 99%

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Transpressional tectonics and Carboniferous magmatism in the Limousin, Massif Central, France: Structural and⁴⁰Ar/³⁹Ar investigations

Gébelin¹,

Brunel

Monié

et al. 2007

Tectonics

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[1] New structural, microstructural, and 40 Ar/ 39 Ar data from the NW Massif Central (France) provide additional constraints on the timing and tectonic setting of late Variscan granite magmatism. Previous studies had emphasized the role of late orogenic extension in the emplacement of granite plutons in the Limousin region. In contrast, the new data set is consistent with syntectonic emplacement of magma in a dextral simple shear active from 350 to 300 Ma in a transpressional regime. As an alternative hypothesis to late orogenic extension, we propose that magmas migrated into tensional bridges between active P shears associated with a lithospheric shear zone comparable to a pop-up structure. The Galician region, in the western end of the Ibero-Armorican tectonic arc, exhibits major left-lateral ductile shear zones which can be interpreted as conjugate structures to the Limousin and Armorican shear zones.

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Section: Discussion In the Scope Of The Geology Of The French Massif mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Transpressional tectonics and Carboniferous magmatism in the Limousin, Massif Central, France: Structural and⁴⁰Ar/³⁹Ar investigations

Gébelin¹,

Brunel

Monié

et al. 2007

Tectonics

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“…A preferred lattice orientation of quartz in gneisses indicates a top to the WNW sense of shear [Quenardel and Rolin, 1984], other criteria clearly support this shearing sense [i.e. sigmoidal pressure shadow, Faure et al, 1990]). …”

Section: The Normal Shear Zones Includementioning

confidence: 99%

“…4). The main movement along the Chambon shear zone [Quenardel and Rolin, 1984], which exhibits a top to the WNW sense of shear [Faure et al, 1990], appears to be synchronous with the intrusion of the Crozant massif (312 ± 20 Ma Rb-Sr datation [Rolin et al, 1982]). This intrusive exhibits a postsolidus foliation and a WNW-ESE stretching lineation.…”

Section: Peraluminous Middle-upper Visean To Namurian Magmatism (340-mentioning

confidence: 99%

Famenno-Carboniferous (370-320 Ma) strike slip tectonics monitored by syn-kinematic plutons in the French Variscan belt (Massif Armoricain and French Massif Central)

Rolin

Marquer

Colchen³

et al. 2009

Bulletin De La Société Géologique De France

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The Variscan continental collision has led to the development of large strike-slip shear zones in western Europe. Our study focuses on the regional deformation and shear zone patterns in the Massif Armoricain and the French Massif Central. The synthesis of granite emplacement ages associated to granite deformation fields, allow us to propose a geodynamic model for the tectonic evolution of this part of the Variscan belt between 370 Ma -320 Ma (Late Devonian -Namurian).After the first steps of the continental subduction-collision, leading to high temperature and anatexis associated with N-S shortening at 380-370 Ma (Frasnian to Famennian), the southern part of the Massif Armoricain and western part of French Massif Central underwent large dextral shearing along N100-N130 trending shear zones up to early Visean time. These large-scale displacements progressively decreased at around 350-340 Ma, during the first emplacements of biotite bearing granites (Moulins-les Aubiers-Gourgé massif and Guéret massif intrusions).During middle Visean times, the shortening axis direction rotated towards a NNE-SSW direction implying changes in the regional deformation field. The occurrence of N070-N100 sinistral and N110-N130 dextral conjugate shear zones within leucogranites are related to that time. Finally, new N150-N160 dextral shear zones appeared in middle to late Visean times: as for examples, the Parthenay and the Pradines shear zones in the SE Massif Armoricain and the Millevaches massif, respectively. These shear zones were conjugated to the sinistral N020 Sillon Houiller in the French Massif Central. They reflect large scale brittle continental indentation in the French Variscan belt during the middle to late Visean. Tectoniques transcurrentes famenno-namuriennes (370-320 Ma) enregistrées par les plutons syn-cinématiques dans la chaîne varisque française (Massifs armoricain et central) Mots-clés. -Varisque, Massif armoricain, Massif central, Zone de cisaillement, Granites, Datations.Résumé. -La collision continentale varisque évolue en Europe occidentale par le développement de zones de cisaillement d'échelle crustale jalonnées d'intrusions granitiques syn-et post-cinématiques. Cette étude se focalise sur les zones de cisaillement qui disloquent cet orogène varisque du Massif armoricain au Massif central, et sur la déformation des granites qui les jalonnent. La synthèse de nombreux âges récents obtenus sur ces granites syn-et post-cinématiques, qui ont enregistrés les différents champs de déformation, permet de proposer un modèle géodynamique pour cette partie de l'orogène entre 370-320 Ma, soit sur la période Dévonien supérieur -Carbonifère inférieur. Au Dévonien moyen-supérieur, la fin de la collision continentale varisque est marquée dans la partie méridionale du Massif armoricain (Vendée) et la partie occidentale du Massif central par une évolution métamorphique de haute température accompagnée d'une anatexie vers 380-370 Ma (Frasnien-Famennnien). Cette évolution est relayée par le développement d'une tectonique trans...

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“…The Variscan Massif Central, France, is known to be a collision belt which first experienced crustal stacking and thickening [Matte, 1986], followed by extension and thinning [Mattauer et al, 1988 ;Faure, 1989 ;Van den Driessche and Brun, 1989 ;Faure et al, 1990 ;Burg et al, 1990 ;Faure, 1995]. Syn-or post-tectonic leucogranite plutons related to the post thickening thermal event crop out over large areas within the Massif Central hiding the earlier crustal structures.…”

Section: Introductionmentioning

confidence: 99%

Late Hercynian leucogranites modelling as deduced from new gravity data : the example of the Millevaches massif (Massif Central, France)

Gébelin

Martelet²,

Brunel

et al. 2004

Bulletin De La Société Géologique De France

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The Millevaches granitic complex, located in the northern part of the French Massif Central, is elongated in a N-S direction, perpendicular to the main E-W trend of the Hercynian belt. It is affected on its limits and in its core by several ductile shear zones that have necessarily played a great role in the emplacement and exhumation of the massif. Based on gravity modelling and recent field observations, this study intends to highlight the massif structure at depth and discuss its mode of emplacement and relations with the surrounding terrains.The new gravity and density measurements on the north-east part of the Millevaches massif improve the gravity coverage of the northern Limousin. Using these new data we model the deep structure of the Millevaches plateau. The density measurements made on the different types of granites of the massif, and on the surrounding terrains improve the interpretation of the Bouguer anomaly. Analysis and inversion of the residual Bouguer anomaly in the area show that the Millevaches massif is 2 to 4 km-thick, from north to south and from west to east, locally rooting down to about 6 km deep in its eastern and southern terminations. These two zones coincide with porphyritic plutons and, because of the complex composite structure of the massif, cannot be definitively interpreted as feeding zones. In the field, the N-S-oriented Pradines vertical fault affects the core of the massif on 4 to 5 km width. Microstructural observations evidence that the faulting is contemporaneous of the granites emplacement. We suggest that this tectonic lineament could have triggered the migration of the magma, although it is not related to a clear gravity anomaly. AMS measurements in the north-central part of the Millevaches massif suggest that the magnetic foliation and lineation display a general sub-horizontal pattern. Moreover, on the western border of the Millevaches massif, the Argentat deep seismic profile shows sub-horizontal layering of gneisses and micaschists and evidences normal faulting offset of this layering along Argentat fault. This agrees fairly well with the gravity results, suggesting that (i) the Millevaches massif would be at a high structural level in the crust, (ii) the exhumation of the massif would have been favoured along the Argentat normal fault. As a whole, the massif can be described as a laccolith, 2 to 4 km-thick, emplaced as a "magmatic lens" into the sub-horizontally foliated gneisses and micaschists. Modélisation des leucogranites tardi-hercyniens à partir de nouvelles données gravimétriques : l'exemple du massif de Millevaches (Massif central)Mots-clés. -Gravimétrie, Densité, Laccolithe, Massif de Millevaches, Structure crustale.Résumé. -Le massif granitique de Millevaches orienté N-S est transverse aux grands chevauchements de la chaîne hercynienne. Il est affecté en son coeur et au niveau de ses bordures par de grandes zones de cisaillement ductiles. On propose que ces accidents aient joué un rôle significatif dans la mise en place et dans les mécanismes d'exhumatio...

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Deformation ductile extensive d'age namuro-westphalien dans le plateau d'Aigurande, Massif central francais

Cited by 26 publications

References 0 publications

Transpressional tectonics and Carboniferous magmatism in the Limousin, Massif Central, France: Structural and⁴⁰Ar/³⁹Ar investigations

Transpressional tectonics and Carboniferous magmatism in the Limousin, Massif Central, France: Structural and⁴⁰Ar/³⁹Ar investigations

Famenno-Carboniferous (370-320 Ma) strike slip tectonics monitored by syn-kinematic plutons in the French Variscan belt (Massif Armoricain and French Massif Central)

Late Hercynian leucogranites modelling as deduced from new gravity data : the example of the Millevaches massif (Massif Central, France)

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Deformation ductile extensive d'age namuro-westphalien dans le plateau d'Aigurande, Massif central francais

Cited by 26 publications

References 0 publications

Transpressional tectonics and Carboniferous magmatism in the Limousin, Massif Central, France: Structural and40Ar/39Ar investigations

Transpressional tectonics and Carboniferous magmatism in the Limousin, Massif Central, France: Structural and40Ar/39Ar investigations

Famenno-Carboniferous (370-320 Ma) strike slip tectonics monitored by syn-kinematic plutons in the French Variscan belt (Massif Armoricain and French Massif Central)

Late Hercynian leucogranites modelling as deduced from new gravity data : the example of the Millevaches massif (Massif Central, France)

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Transpressional tectonics and Carboniferous magmatism in the Limousin, Massif Central, France: Structural and⁴⁰Ar/³⁹Ar investigations

Transpressional tectonics and Carboniferous magmatism in the Limousin, Massif Central, France: Structural and⁴⁰Ar/³⁹Ar investigations