Tectonic evolution and global crustal architecture of the European Variscan belt constrained by geophysical data

Schulmann, Karel; Edel, Jean–Bernard; Catalán, José R. Martı́nez; Mazur, Stanisław; Alfonso, Guy; Lardeaux, Jean‐Marc; Ayarza, P.; Palomeras, Imma

doi:10.1016/j.earscirev.2022.104195

Cited by 31 publications

(14 citation statements)

References 240 publications

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“…The different architecture of the eastern part of the European Variscan belt is also supported by geophysical identification of two parallel and south‐dipping belts associated with dense bodies separating the Saxothuringian basement from the Teplá‐Barrandian Zone upper plate and the Central Armorican Domain from the French Massif Central (Schulmann et al., 2022; Figure 1). The structurally higher belt of reflectors is interpreted as a remnant of the Mid‐Variscan Ocean closed during Upper Devonian (Collett et al., 2022), while the structurally deeper reflectors are located above the high‐velocity and high‐density zone representing a deeply subducted continental margin of the Saxothruringian block beneath the Mid‐Variscan Allochthon during early Carboniferous (Konopásek et al., 2019).…”

Section: Discussionmentioning

confidence: 80%

Assembly of the Variscan Orogenic Wedge in the Bohemian Massif: Monazite U‐Pb Geochronology of the Tectonic Events Recorded in Saxothuringian Metasediments

et al. 2023

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The most spectacular manifestation of plate tectonics is the formation of orogenic belts. A popular geodynamic model explaining the formation of collisional orogens is the wedge model (e.g., Dahlen et al., 1984;Malavieille, 2010;Platt, 1986;Willett et al., 1993), originally applied to accretionary wedges formed above subducting plates. However, the geodynamic evolution of many collisional orogens involves the closure of oceanic domains followed by continental collision resulting in a protracted evolution and transition from accretionary to orogenic wedge systems. Such evolution then reflects the pre-collisional subduction of an oceanic lithosphere, the associated formation and exhumation of Ultra-High-Pressure (UHP) rocks and the subduction of buoyant crustal material (e.g., Beaumont et al., 1996;Burov et al., 2014;Sizova et al., 2014) leading to a complex polyphase structural and metamorphic record.European Variscides (Figure 1) are the major segment of a large orogenic system resulting from progressive closure of the Rheic Ocean which separated Gondwana and Laurussia. Despite the major along strike variations in orogenic architecture and provenience of individual tectono-metamorphic units (Martínez Catalán et al., 2020), the tectonic evolution and timing of major events could be successfully correlated (Catalan et al., 2021) between individual segments of the orogenic belt. The Erzgebirge Crystalline Complex, representing part of the Saxothuringian Domain in the Bohemian Massif, preserves numerous occurrences of eclogite-and blueschist-facies rocks with UHP relics pointing to a subduction environment in an orogenic wedge setting (e.g.,

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Section: Discussionmentioning

confidence: 80%

Assembly of the Variscan Orogenic Wedge in the Bohemian Massif: Monazite U‐Pb Geochronology of the Tectonic Events Recorded in Saxothuringian Metasediments

et al. 2023

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“…From the perspective of this model invoking a southward subduction and subsequent southward migration of the partially exhumed material, it is interesting to note that a similar southward flow of migmatite-hosted eclogites has been proposed in the southernmost part of the FMC, between the Lévézou and the Montagne Noire F I G U R E 1 4 Sketch of the main Variscan massifs and terranes of the European Variscan orogen (modified after Martínez Catal an et al, 2007, and Schulmann et al, 2022 highlighting the possible correlations between the eastern French Massif Central and the Bohemian Massif based on the occurrence and age of the Devono-Carboniferous HP-HT rocks and the location of the associated arc and back-arc systems. Differences between the correlations before and after the present contribution can be seen by comparison with Figure 1a.…”

Section: Implications For the Tectonic Evolution Of The Fmcmentioning

confidence: 96%

“…From this perspective, the lithological and geochemical zoning of the Morvan–Brévenne area suggesting a southward subduction may be regarded as carrying a first‐order message. The suture zone situated to the north of the FMC (e.g., Ballèvre et al, 2009; Baptiste et al, 2016; Schulmann et al, 2022) would result from a late Devonian subduction dipping to the south (e.g., Faure et al, 1997; Pin et al, 1982), which promoted the development of the arc and back‐arc domains in the Brévenne and Morvan areas (Pin & Paquette, 2002). The Devono–Carboniferous age of the eclogites determined here suits within the proposed timing of a north‐lying, south‐dipping subduction.…”

Section: Tectonic Implicationsmentioning

confidence: 99%

“…Sketch of the main Variscan massifs and terranes of the European Variscan orogen (modified after Martínez Catalán et al, 2007, 2021, and Schulmann et al, 2022) highlighting the possible correlations between the eastern French Massif Central and the Bohemian Massif based on the occurrence and age of the Devono–Carboniferous HP‐HT rocks and the location of the associated arc and back‐arc systems. Differences between the correlations before and after the present contribution can be seen by comparison with Figure 1a.…”

Section: Tectonic Implicationsmentioning

confidence: 99%

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Complex geochronological record of an emblematic Variscan eclogite (Haut‐Allier, French Massif Central)

Marien

Pitra

Poujol

et al. 2023

Journal Metamorphic Geology

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Two eclogite samples from the Haut-Allier record a prograde evolution from $20 kbar, 650 C to 750 C, 22-23 kbar followed by heating up to 850-875 C and partial melting. Incipient decompression in high-pressure granulite facies conditions (19.5 kbar, 875 C) was followed by exhumation to high-temperature amphibolite facies conditions (<9 kbar, 750-850 C). Following a detailed geochemical, petrological, and geochronological investigation using trace-element data and laser ablation inductively coupled plasma mass spectrometry U-Pb dating of zircon, apatite, and rutile, the eclogites reveal an Ordovician (c. 490 Ma) rifting event followed by Devonian (c. 370-360 Ma) subduction and Carboniferous (c. 350 Ma) exhumation in this part of the French Massif Central. The previously proposed Silurian age for the subduction, which strongly influenced many tectonic models, is definitively rejected. In the light of other geological data from the French Massif Central, including the lithological and geochemical zoning of calc-alkaline Devonian volcanism, we propose a southward polarity of the subduction and question the very existence of the so-called Massif Central Ocean. Furthermore, we infer that following subduction, the eclogites were relaminated to the upper plate and exhumed at the rear of the magmatic arc pointing to similarities with the geodynamics of the Bohemian Massif. The petrochronological record of zircon is particularly complex. Metamorphic zircon with clear eclogitic rare-earth elements patterns (no Eu anomaly and flat heavy rare-earth elements) and inclusions (garnet, rutile, and omphacite)shows concordant apparent ages that spread from c. 380 down to c. 310 Ma. This apparent age pattern strongly contrasts with the well-defined age of apatite and rutile of c. 350 Ma. Apparent zircon ages younger than 350 Ma unequivocally testify that zircon can recrystallize outside the conditions of the eclogite facies, which resets the U-Pb while preserving an apparent eclogitic signature. Local fractures filled by analcite, thomsonite, plagioclase, and biotite testify to late interaction of the eclogites with alkaline fluids at relatively low temperatures. This interaction, possibly at c. 310 Ma or later, could lead to the recrystallization of zircon while leaving apatite unaffected.

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“…Following these last studies, eclogite facies metamorphism is Devonian (400-365 Ma) and thus coeval with the development, at the scale of the entire European Variscan belt, of arc and back-arc magmatic systems drawing a nowadays hidden subduction system [Schulmann et al, 2022]. In this framework, the Montagne Noire eclogites (southern FMC) offer a different scenario, with conditions of higher temperature and an age of 310 Ma [Whitney et al, 2020].…”

Section: Continental Collision Zones With Hidden Subduction Pattern A...mentioning

confidence: 99%

Metamorphism and linked deformation in understanding tectonic processes at varied scales

Lardeaux¹

2024

Comptes Rendus. Géoscience

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This contribution presents a review exploring some aspects and issues surrounding the links between metamorphism and deformation at different scales. I first discuss the quantification methods of thermodynamics and the parameters able to overcome the kinetic barriers for metamorphic reactions. On the basis of some world's type iconic examples I discuss how metamorphism is likely to portray the thermo-mechanical evolution of lithosphere active zones, thus large-scale tectonic processes. Finally, I present the multiple interactions between metamorphism and deformation at rock and outcrop scales.

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Tectonic evolution and global crustal architecture of the European Variscan belt constrained by geophysical data

Cited by 31 publications

References 240 publications

Assembly of the Variscan Orogenic Wedge in the Bohemian Massif: Monazite U‐Pb Geochronology of the Tectonic Events Recorded in Saxothuringian Metasediments

Assembly of the Variscan Orogenic Wedge in the Bohemian Massif: Monazite U‐Pb Geochronology of the Tectonic Events Recorded in Saxothuringian Metasediments

Complex geochronological record of an emblematic Variscan eclogite (Haut‐Allier, French Massif Central)

Metamorphism and linked deformation in understanding tectonic processes at varied scales

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