The Variscan orogeny: extent, timescale and the formation of the European crust

Schulmann, Karel; Catalán, José R. Martı́nez; Lardeaux, J. M.; Janoušek, Vojtěch; Oggiano, G.

doi:10.1144/sp405.15

Cited by 60 publications

(28 citation statements)

References 24 publications

(17 reference statements)

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“…The zircon U-Pb age of 473.4 ± 2 Ma obtained in this study, similar to the age of the emplacement of the adjacent granite dated at 468.2 ± 2.7 , provides new evidence of the bimodal character of this massive magmatic event recorded during the Ordovician (e.g., Iberian Massif -e.g., Sánchez-García et al, 2003, 2008Villaseca et al, 2015;Del Grecco et al, 2016;Gutiérrez-Alonso et al, 2016;García-Arias et al, 2018; Armorican Massif -e.g.,, Ballèvre et al, 2012French Massif Centrale.g.,, Pitra et al, 2012;Chelle-Michou et al, 2017;Lotout et al, 2017;Sardinia -e.g.,, Helbing & Tieppolo, 2005;Oggiano et al, 2010;Caggero et al, 2012;Bohemian Massife.g., Košler et al, 2004;Linnemann et al, 2008), related to the extreme stretching of the lithosphere (e.g., Bard et al, 1980;Matte & Burg, 1981;Matte, 1986;Pin, 1990;Ribeiro et al, 2007;Martínez Catalán et al, 2009;Lardeaux, 2014;Schulmann et al, 2014).…”

Section: Eclogite Protoliths: Origin and Emplacement Settingmentioning

confidence: 99%

From Burial to Exhumation: Emplacement and Metamorphism of Mafic Eclogitic Terranes Constrained Through Multimethod Petrochronology, Case Study from the Lévézou Massif (French Massif Central, Variscan Belt)

Lotout

Poujol

Pitra

et al. 2020

Journal of Petrology

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Linking mineral growth and time is required to unravel the evolution of metamorphic rocks. However, dating early metamorphic stages is a challenge due to subsequent retrograde overprinting. A fresh eclogite and a former eclogite retrogressed under amphibolite facies from the southern French Massif Central (Lévézou massif, Variscan belt) were investigated with a large panel of geochronometers (U–Pb in zircon, rutile and apatite, Lu–Hf and Sm–Nd in garnet) in a petrological context tightly constrained by petrographic observations, trace element analyses and phase equilibrium modelling. Both samples recorded similar HP conditions at 18–23 kbar and 680–800°C, whereas the retrogressed eclogite later equilibrated at 8–9·5 kbar and c.600°C. In the retrogressed sample, most of the zircon grains are characterized by negative Eu anomalies and HREE enrichment, and yield an Ordovician U–Pb date of 472·3 ± 1·7 Ma, interpreted as the emplacement age of the mafic protolith. In agreement with other data available for the Variscan belt, and based on zircon trace element record and whole-rock geochemistry, this age is considered to represent the magmatism associated with the extreme thinning of the continental margins during the Ordovician. In the same sample, a few zircon rims show a weaker HREE enrichment and yield a date of 378 ± 5·7 Ma, interpreted as a prograde pre-eclogitic age. Lu–Hf garnet dating from both samples yields identical dates of 357 ± 13 Ma and 358·0 ± 1·5 Ma inferred to approximate the age of the high-pressure metamorphic peak. Fresh and retrogressed samples yield respectively 350·4 ± 7·7 Ma and 352 ± 20 Ma dates for Sm–Nd garnet dating, and 367·8 ± 9·1 Ma and 354·9 ± 9·5 Ma for U–Pb rutile dating. Apatite grains from the retrogressed sample give a mean age of 351·8 ± 2·8 Ma. The similarity between all recorded ages from distinct chronometers and radiometric methods (U–Pb, rutile, apatite; Lu–Hf, garnet; Sm–Nd, garnet) combined with P–T estimations from high-pressure metamorphic rocks equilibrated under different conditions testifies to very fast processes that occurred during the Variscan orogeny, highlighting a major decompression of 15–8·5 kbar in less than 7 Myr, and suggesting mean exhumation rates in excess of 6·3 mm/yr.

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Section: Eclogite Protoliths: Origin and Emplacement Settingmentioning

confidence: 99%

From Burial to Exhumation: Emplacement and Metamorphism of Mafic Eclogitic Terranes Constrained Through Multimethod Petrochronology, Case Study from the Lévézou Massif (French Massif Central, Variscan Belt)

Lotout

Poujol

Pitra

et al. 2020

Journal of Petrology

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“…Throughout the Vosges, a complex suite of Carboniferous magmatic rocks intruded into the early Palaeozoic-Carboniferous basement, predominantly comprising clastic metasedimentary rocks. Over the last three decades, these distinct magmatic suites have instigated significant interest and research into the study of Variscan tectonics and magmatic evolution [13]. et Minières (BRGM) public domain data [4,5] led to the delineation of a distinct W anomaly in the Natzwiller Granite, which is located in the northern domain of the Vosges Mountains.…”

Section: Regional Geological Settingmentioning

confidence: 99%

“…Throughout the Vosges, a complex suite of Carboniferous magmatic rocks intruded into the early Palaeozoic-Carboniferous basement, predominantly comprising clastic metasedimentary rocks. Over the last three decades, these distinct magmatic suites have instigated significant interest and research into the study of Variscan tectonics and magmatic evolution [13]. [12] and (b) geological map of the northern Vosges Mountains with focus on the Champ du Feu area, NE France (modified from Bureau de Recherches Géologiques et Minières (BRGM) InfoTerre [4]).…”

Section: Regional Geological Settingmentioning

confidence: 99%

An Exploration Study of the Kagenfels and Natzwiller Granites, Northern Vosges Mountains, France: A Combined Approach of Stream Sediment Geochemistry and Automated Mineralogy

2019

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Following a regional reconnaissance stream sediment survey that was carried out in the northern Vosges Mountains in 1983, a total of 20 stream sediment samples were collected with the aim of assessing the regional prospectivity for the granite-hosted base and rare metal mineralisation of the northern Vosges magmatic suite near Schirmeck. A particular focus of the investigation was the suspected presence of W, Nb and Ta geochemical occurrences in S-type (Kagenfels) and I-S-type (Natzwiller) granites outlined in public domain data. Multi-element geochemical assays revealed the presence of fault-controlled Sn, W, Nb mineralisation assemblages along the margins of the Natzwiller and Kagenfels granites. Characteristic geochemical fractionation and principal component analysis (PCA) trends along with mineralogical evidence in the form of cassiterite, wolframite, ilmenorutile and columbite phases and muscovite–chlorite–tourmaline hydrothermal alteration association assemblages in stream sediments demonstrate that, in the northern Vosges, S-type and fractionated hybrid I-S-type granites are enriched in incompatible, late-stage magmatic elements. This is attributed to magmatic fractionation and hydrothermal alteration trends and the presence of fluxing elements in late-stage granitic melts. This study shows that the fractionated granite suites in the northern Vosges Mountains contain rare metal mineralisation indicators and therefore represent possible targets for follow-up mineral exploration. The application of automated mineralogy (QEMSCAN®) in regional stream sediment sampling added significant value by linking geochemistry and mineralogy.

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“…Variscan fragments are recognized all over the Alpine Belt of Europe (Dallmeyer et al 1998;Neubauer & Handler 1999;Franke et al 2000;Kroner et al 2008;Froitzheim et al 2008;Schulmann et al 2014 and references therein). Although in the Balkans high-grade metamorphic rocks from the deep structural levels of the European Variscan Belt are well-exposed (Ivanov 1988;Kräutner & Kristic 2002;Iancu et al 2005;Yanev et al 2006;Kounov et al 2012;Gerdjikov et al 2013) (Fig.…”

Section: Introductionmentioning

confidence: 99%

Cambrian magmatism, Variscan high-grade metamorphism and imposed greenschist facies shearing in the Central Sredna Gora basement units (Bulgaria)

Lazarova¹,

Naydenov²,

Petrov³

et al. 2015

Geologica Carpathica

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Gneisses from the deep structural levels of the European Variscan Belt are well exposed in the Central Sredna Gora in Bulgaria. In general, migmatites predominate, but unmigmatized domains (or domains with incipient migmatization) are also documented in this area. This paper presents new structural, petrographic and U-Pb isotope geochronological data from such an unmigmatized part of the Variscan high-grade metamorphic basement (the Koprivshtitsa Unit). A predominant part of this unit represents an alternation of metagranitoids and metabasites. The protolith crystallization age of the metagranitoids is constrained at 491.5 ± 7.6 Ma by U-Pb laser ablation method on zircons. This age coincides with the previously available Late Cambrian protolith ages of metabasic rocks that crop out within the adjacent migmatitic unit. The Korpivshtitsa Unit comprises also lesser orthogneisses with Late Neoproterozoic protoliths. Based on the available local and regional paleogeographic reconstruction schemes, we suggest that the Upper Cambrian magmatic rocks intruded Upper Neoproterozoic crust during the initial opening stages of the Rheic Ocean or a related basin. Subsequently, both were involved in the Variscan high-grade deformation. The contact of the Koprivshitsa Unit with the migmatitic part of the metamorphic complex coincides with a north-vergent greenschist facies thrust zone – the Chuminska Shear Zone. The exact time of the shearing is still not well constrained but it clearly postdates the Variscan high-temperature metamorphism of the gneisses.

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The Variscan orogeny: extent, timescale and the formation of the European crust

Cited by 60 publications

References 24 publications

From Burial to Exhumation: Emplacement and Metamorphism of Mafic Eclogitic Terranes Constrained Through Multimethod Petrochronology, Case Study from the Lévézou Massif (French Massif Central, Variscan Belt)

From Burial to Exhumation: Emplacement and Metamorphism of Mafic Eclogitic Terranes Constrained Through Multimethod Petrochronology, Case Study from the Lévézou Massif (French Massif Central, Variscan Belt)

An Exploration Study of the Kagenfels and Natzwiller Granites, Northern Vosges Mountains, France: A Combined Approach of Stream Sediment Geochemistry and Automated Mineralogy

Cambrian magmatism, Variscan high-grade metamorphism and imposed greenschist facies shearing in the Central Sredna Gora basement units (Bulgaria)

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