Les complexes leptyno-amphiboliques (C.I.A.); revue critique et suggestions pour un meilleur emploi de ce terme

Santallier, Danielle; Briand, B.; Ménot, René-Pierre; Piboule, Michel

doi:10.2113/gssgfbull.iv.1.3

Cited by 51 publications

(16 citation statements)

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“…They contain metre-to decametre-scale boudins of less deformed intermediate to mafic garnet-clinopyroxeneplagioclase granulites. In proximity to the Fautea village, the granulites pass abruptly to stromatic migmatites, that are intercalated with amphibolitefelsic gneisses sequences (previously referred to as leptynite-amphibolites: Pin & Piboule, 1988;Santallier et al, 1988) as well as with massive amphibolite . The foliation traces in the gneisses are extrapolated from local measurement and are only indicative of regional trends.…”

Section: Fautea-solenzara Unit: the Granulite-bearing Complexmentioning

confidence: 99%

Exhumation of a Variscan orogenic complex: insights into the composite granulitic–amphibolitic metamorphic basement of south‐east Corsica (France)

Giacomini

Dallai

Carminati

et al. 2008

Journal Metamorphic Geology

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A structural, petrological and geochronological (U-Th-Pb of zircon and monazite) study reveals that the lower crust sequences of the Variscan high-grade basement cropping out between Solenzara and Porto Vecchio, south-east Corsica (France) have been tectonically juxtaposed along with middle crustal rocks during the extrusion of the orogenic root of the Variscan chain. We propose that a system of hightemperature, orogen-parallel shear zones that developed under a transpressive dextral tectonic regime caused the exhumation of the entire sequence. This tectonic complex is thus made up of rocks having undergone different P-T conditions (eclogite-?, high-pressure granulite facies and amphibolite facies) at different times, reflecting the progressive foreland migration of the orogenic front. The Solenzara granulites were derived from burial of continental crust to high-pressure (1.8-1.4 GPa) and high-to ultrahigh-temperature conditions (900-1000°C) during the Variscan convergence: U-Pb ELA-ICPMS zircon dating constrained the timing of this metamorphism at c. 360 Ma. The gneisses cropping out at Porto Vecchio are middle crustal-level rocks that reached their peak temperature conditions (700-750°C at <1.0 GPa) at c. 340 Ma. The diachronism of the metamorphic events, the foliation patterns and their geometry suggest that the granulites were exhumed to middle crustal levels through channel flow tectonics under continuous compression. The amphibolite facies gneisses of Porto Vecchio and the granulites of Solenzara were accreted through the development of a major dextral mylonitic zone forming under amphibolite facies conditions: in situ monazite isotope dating (ELA-ICPMS) revealed that this deformation occurred at c. 320 Ma and was accompanied by the emplacement of syntectonic high-K melts. A final HTLP static overprint, constrained at 312-308 Ma by monazite U-Th-Pb isotope dating, is related to the emplacement of the igneous products of the Sardinia-Corsica batholith and marks the transition from the Variscan orogenic event to the Permian extension.

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Section: Fautea-solenzara Unit: the Granulite-bearing Complexmentioning

confidence: 99%

Exhumation of a Variscan orogenic complex: insights into the composite granulitic–amphibolitic metamorphic basement of south‐east Corsica (France)

Giacomini

Dallai

Carminati

et al. 2008

Journal Metamorphic Geology

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“…Two gneissic units are distinguished throughout most of the Massif Central (Burg et al, 1984;Santallier et al, 1988;Ledru et al, 1989Ledru et al, , 1994Ledru et al, 1994;Lardeaux et al, 2001) ( Fig. 2a): The upper gneiss unit (UGU) contains HP metamorphic assemblages (up to 28 kbar; Lardeaux et al, 2001).…”

Section: Major Tectono-metamorphic Eventsmentioning

confidence: 99%

Syntectonic crustal melting and high-grade metamorphism in a transpressional regime, Variscan Massif Central, France

2009

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Hot collisional orogens are characterized by abundant syn-kinematic granitic magmatism that profoundly affects their tectono-thermal evolutions. Voluminous granitic magmas, emplaced between 360 and 270 Ma, played a visibly important role in the evolution of the Variscan Orogen. In the Limousin region (western Massif Central, France), syntectonic granite plutons are spatially associated with major strike-slip shear zones that merge to the northwest with the South Armorican Shear Zone. This region allowed us to assess the role of magmatism in a hot transpressional orogen. Microstructural data and U/Pb zircon and monazite ages from a mylonitic leucogranite indicate synkinematic emplacement in a dextral transpressional shear zone at 313 +/- 4 Ma. Leucogranites are coeval with cordierite-bearing migmatitic gneisses and vertical lenses of leucosome in strike-slip shear zones. We interpret U/Pb monazite ages of 315 +/- 4 Ma for the gneisses and 316 +/- 2 Ma for the leucosomes as the minimum age of high-grade metamorphism and migmatization respectively. These data suggest a spatial and temporal relationship between transpression, crustal melting, rapid exhumation and magma ascent, and cooling of high-grade metamorphic rocks.;Some granites emplaced in the strike-slip shear zone are bounded at their roof by low dip normal faults that strike N-S, perpendicular to the E-W trend of the belt. The abundant crustal magmatism provided a low-viscosity zone that enhanced Variscan orogenic collapse during continued transpression, inducing the development of normal faults in the transpression zone and thrust faults at the front of the collapsed orogen

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“…[8] The Middle Devonian to Early Carboniferous recorded continental collision and nappe stacking. Two gneissic units are distinguished in most parts of Massif Central [Burg et al, 1984;Santallier et al, 1988Santallier et al, , 1994Ledru et al, 1989Ledru et al, , 1994aLardeaux et al, 2001]. The upper gneiss unit (UGU) contains HP metamorphic assemblages and is characterized, at its base, by a bimodal association, the so-called ''leptyno-amphibolite'' group.…”

Section: Geological Setting and Previous Workmentioning

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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[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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Les complexes leptyno-amphiboliques (C.I.A.); revue critique et suggestions pour un meilleur emploi de ce terme

Cited by 51 publications

References 0 publications

Exhumation of a Variscan orogenic complex: insights into the composite granulitic–amphibolitic metamorphic basement of south‐east Corsica (France)

Exhumation of a Variscan orogenic complex: insights into the composite granulitic–amphibolitic metamorphic basement of south‐east Corsica (France)

Syntectonic crustal melting and high-grade metamorphism in a transpressional regime, Variscan Massif Central, France

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

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Les complexes leptyno-amphiboliques (C.I.A.); revue critique et suggestions pour un meilleur emploi de ce terme

Cited by 51 publications

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Exhumation of a Variscan orogenic complex: insights into the composite granulitic–amphibolitic metamorphic basement of south‐east Corsica (France)

Exhumation of a Variscan orogenic complex: insights into the composite granulitic–amphibolitic metamorphic basement of south‐east Corsica (France)

Syntectonic crustal melting and high-grade metamorphism in a transpressional regime, Variscan Massif Central, France

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

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