Collapse of the thickened Variscan crust in the French Massif Central: Mont Pilat extensional shear zone and St. Etienne Late Carboniferous basin

Malavieille, Jacques; Guihot, P.; Costa, Sylvie; Lardeaux, Jean‐Marc; Gardien, Véronique

doi:10.1016/0040-1951(90)90278-g

Cited by 195 publications

(100 citation statements)

References 47 publications

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“…S-type granites were intruded at the end of the process, between 330 and 275 m. y. Similar processes took place in other segments of the Hercynian Belt (Malavielle et al, 1990 ;Se ranne, 1992 ). High relief and thick crust are stable while compression at the edges of the belt is maintained, but after its ce ssation, gravitational instability re sults in a short period of time (Bird, 1979;Houseman et al ., 1981;Glazer and Bartley, 1985).…”

Section: The Orientation Of the Iberian Basin And Its Relations With mentioning

confidence: 60%

Origin of the Permian-Triassic Iberian Basin, central-eastern Spain

Arché¹,

López-Gómez²

1996

Tectonophysics

128

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The Iberian Basin was an intracratonic rift basin in central-eastern Spain developed since Early Permian times. The basin boundary faults were normal, listric faults controlling an asymmetric extension propagating northeast with time.Hercynian or older lineaments controlled the orientation of the Iberian Basin and extension was accommodated basically in the hanging wall block by the formation of secondary grabens and a central high. The basin was related with the coeval Ebro, Catalan and Cuenca-Mancha Basins and their connections are discussed.Subsidence curves show that the Early Permian-Early Jurassic period of extension can be subdivided into three rifting episodes and a flexural one. Extension factor increases from 1.17 in the northwest to 1.29 near the Mediterranean coast.The increasing extension rate was accommodated by transfer faults trending NNE-SSW, more important in the Levante area. The rift evolution is intermittent and seems to reflect distinct stress fields.The collapse of the late Hercynian orogen and related increased heat flux, extension and rifting is the most probable origin of the Iberian Basin and related basins. The origin of the Catalan and the Valencia-Prebetic Basins is related to the southwards migration of the Hesse-Burgundy Rift along the eastern margin of the Iberian Microplate.

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Section: The Orientation Of the Iberian Basin And Its Relations With mentioning

confidence: 60%

Origin of the Permian-Triassic Iberian Basin, central-eastern Spain

Arché¹,

López-Gómez²

1996

Tectonophysics

128

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“…Therefore, it is hard to decide whether they are a volumetrically minor, or significant, component; and how much heat they could have transferred to the crust. Alternately, vaugnerites could just be the result of the same process that independently caused the heating of the crust: slab breakoff (Davies and von Blanckenburg 1995;van de Zedde and Wortel 2001;Atherton and Ghani 2002;Janoušek and Holub 2007), delamination of a lithospheric mantle root (Houseman et al 1981;Houseman and Molnar 2001;Molnar and Houseman 2004) or orogenic collapse (England and Thompson 1984;Malavieille et al 1990;Gardien et al 1997;Rey et al 2001;Vanderhaeghe and Teyssier 2001). All these processes would result in sudden heating of the crust, as well as concomitant generation of mafic melts (Arnold et al 2001;Clark et al 2011;Lexa et al 2011).…”

Section: Vaugnerites and The M 3 -M 4 Transitionmentioning

confidence: 99%

Temporal relationships between Mg-K mafic magmatism and catastrophic melting of the Variscan crust in the southern part of Velay Complex (Massif Central, France)

Couzinié¹,

Moyen²,

Villaros³

et al. 2014

Jour. Geosci.

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Mg-K mafic intrusive rocks are commonly observed during the late stages of the evolution of orogenic belts. The Variscan French Massif Central has many outcrops of these rocks, locally called vaugnerites. Such magmas have a mantle-derived origin and therefore allow discussion of the role of mantle melting and crust-mantle interactions during late-orogenic processes. In the Southern Velay area of the French Massif Central, LA-ICPMS U-Pb dating on zircons and monazites from three vaugnerites and four coeval granites reveals that the two igneous suites formed simultaneously, at c. 305 Ma. This major igneous event followed after an early, protracted melting stage that lasted for 20-30 My and generated migmatites, but the melt was not extracted efficiently and therefore no granite plutons were formed. This demonstrates that widespread crustal anatexis, melt extraction and granite production were synchronous with the intrusion of vaugneritic mantle-derived melts in the crust. The rapid heating and subsequent melting of the crust led to upward flow of partially molten rocks, doming and collapse of the belt.

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“…In the marginal zones, low-grade metamorphic rocks commonly have a steep-dipping foliation, whereas high-grade rocks near the core of the dome commonly display a shallow-dipping foliation. The tectonic models evoked for dome development fall into four * Author for correspondence: mezger@uni-mainz.de broader categories: (1) compression, which includes the diapirism (Ramberg, 1980;Soula, 1982) and transpression (Carreras & Capella, 1994;Gleizes, Leblanc & Bouchez, 1997) models; (2) extension, which comprises models of crustal thinning in an extensional setting, known as metamorphic core complexes (Lister & Davis, 1989;Malavielle et al 1990;Oliver, 1994;Hetzel et al 1995;Dirks, Zhang & Passchier, 1997) and coupled crustal thinning and diapirism (Teyssier & Whitney, 2002); (3) a combination of compression followed by extension or doming (Zwart, 1986;Gibson, 1989Gibson, , 1991Aerden, 1994Aerden, , 1998; and (4) interference of polyphase intrusions with large-scale folds and flat-lying shear zones (Passchier, 1994;Myers, 1995;Zegers et al 1998). Eeckhout & Zwart (1988) and Gleizes, Leblanc & Bouchez (1997).…”

Section: Introductionmentioning

confidence: 99%

Polymetamorphism and ductile deformation of staurolite–cordierite schist of the Bossòst dome: indication for Variscan extension in the Axial Zone of the central Pyrenees

Mezger

Passchier

2003

Geol. Mag.

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-The Bossòst dome is an E-W-trending elongated structural and metamorphic dome developed in Cambro-Ordovician metasedimentary rocks in the Variscan Axial Zone of the central Pyrenees. A steep fault separates a northern half-dome, cored by massif granite, from an E-W-trending doubly plunging antiform with granitic sills and dykes in the core to the south. The main foliation is a flat-lying S 1/2 schistosity that grades into a steeper-dipping slaty cleavage at the dome margins. Three major deformational and two metamorphic phases can be differentiated. S 1/2 schistosity is an axial planar cleavage to W-vergent recumbent folding that probably occurred in mid-Westphalian time. Peak regional metamorphism M 1 is characterized by static growth of staurolite and garnet following thermal relaxation of the previously thickened crust. Strong non-coaxial deformation recording uniform topto-the-SE extension during D 2a is preserved in staurolite-garnet schists in a 1.5 km thick, shallowly SE-dipping zone in the southeastern dome. A 500 m thick contact aureole (M 2 ) was imprinted on the regionally metamorphosed rocks following the intrusion the Bossòst granite during D 2b . More coaxial deformation prevailed during synkinematic growth of M 2 phases in the inner part of the contact aureole around the northern part of the dome, where it obliterated D 2a fabrics. Progressive non-coaxial deformation continued in the southeastern antiform and is recorded by late-synkinematic growth of cordierite. Successive overprinting of the M 1 staurolite-garnet assemblage by andalusite and cordierite of M 2 is preserved in the southern part. The assemblage muscovite + cordierite + staurolite + biotite is considered metastable, given the low Mn and Zn contents of staurolite and cordierite, and interpreted as the result of prograde metamorphism during decompression. P-T conditions during M 2 were approximately 3 kbar and 600• C. Pervasive crenulations and mesoscopic to regional southerly verging folds are the result of D 3 NNE-SSW compression post-dating ductile deformation and contact metamorphism. Polymetamorphic assemblages of the Bossòst dome preserve a regionally confined zone of ESE-directed extensional shearing within an overall N-S compressional setting. Exact timing of extensional shearing is not known, but can be constrained by recumbent folding during the midWestphalian and granitic intrusions, which confine it to Late Carboniferous time (c. 305 Ma). Crustalscale flat-lying extensional shear zones with similar orientation and time frame are observed in the Hospitalêt massif of the eastern Axial Zone. This suggests that crustal extension, though probably restricted by regional strain partitioning over orthogneiss or intruding granitic bodies within an overall compressive setting, was not uncommon in Late Carboniferous time in the Axial Zone of the Pyrenees.

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Collapse of the thickened Variscan crust in the French Massif Central: Mont Pilat extensional shear zone and St. Etienne Late Carboniferous basin

Cited by 195 publications

References 47 publications

Origin of the Permian-Triassic Iberian Basin, central-eastern Spain

Origin of the Permian-Triassic Iberian Basin, central-eastern Spain

Temporal relationships between Mg-K mafic magmatism and catastrophic melting of the Variscan crust in the southern part of Velay Complex (Massif Central, France)

Polymetamorphism and ductile deformation of staurolite–cordierite schist of the Bossòst dome: indication for Variscan extension in the Axial Zone of the central Pyrenees

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