Late Visean hidden basins in the internal zones of the Variscan belt: U-Pb zircon evidence from the French Massif Central

Bruguier, Olivier; Becq-Giraudon, Jean-François; Bosch, Delphine; Lancelot, Joël

doi:10.1130/0091-7613(1998)026<0627:lvhbit>2.3.co;2

Cited by 39 publications

(27 citation statements)

References 16 publications

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“…Zircons extracted from fireclays in the lowermost part of the sedimentary sequence of the Bosmoreau coal basin at the northern end of the Argentat fault ( Fig. 6) also provide a Late Visean age of 332 4 Ma (Bruguier et al 1998). The Argentat fault is the western boundary of the Millevaches plateau ( Fig.…”

Section: Importance and Significance Of The Late Visean Tectono-thermmentioning

confidence: 97%

Late Visean thermal event in the northern part of the French Massif Central: new 40Ar/39Ar and Rb–Sr isotopic constraints on the Hercynian syn-orogenic extension

Faure

Monié

et al. 2000

Int J Earth Sci

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The French Massif Central belongs to the central metamorphic domain of the European Hercynian Belt. 40 Ar/ 39 Ar mica and amphibole dates have been obtained on magmatic and metamorphic rocks from the northern part of the French Massif Central (Sioule and BrØvenne-Violay series). The 336-to 337-Ma dates recorded by a granodiorite (the St. Gervais pluton) and its mylonitic border along the Ste Christine fault and the 3375-Ma muscovite ages from the BrØvenne series are consistent with the age of wrenching related to the late stage of the Hercynian compression. The remaining age spectra from the Sioule area provide ages ranging from 331 to 335 Ma that are interpreted as cooling ages related to rock exhumation after the main stages of metamorphism and deformation in the studied area. Late Visean dates widespread in North Massif Central correspond to a huge magmatic event characterized by the emplacement of ªred granitesº, granophyres and subaerial acidic volcanics known as the ªTufs anthracifresº formation. Rb±Sr isotopic data from volcanic and hypovolcanic rocks from the Sioule and Montagne Bourbonnaise areas place constraints on the source of the magmas. Simple metapelite crustal melting or a major contribution from depleted mantle sources are ruled out, and instead, mantle-derived magmas were probably involved, at least as a heat source, during the Late Visean magmatism. Exhumation and cooling of metamorphic rocks below 300 C occurred contemporaneously with this Late Visean magmatism. In the geodynamic evolution of the Hercynian Belt, the Late Visean (ca. 335±330 Ma) magmatism corresponds to a major break marking the onset of post-collisional extension in the inner zone which had been thickened by collision in Latest Devonian±Earliest Carboniferous. This Late Visean extension in the inner zone which is synchronous to compression in the northern and southern forelands of the belt appears as a synorogenic process.

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Section: Importance and Significance Of The Late Visean Tectono-thermmentioning

confidence: 97%

Late Visean thermal event in the northern part of the French Massif Central: new 40Ar/39Ar and Rb–Sr isotopic constraints on the Hercynian syn-orogenic extension

Faure

Monié

et al. 2000

Int J Earth Sci

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“…Lithological similarities have been drawn between the thick (>400 m) rhyodacitic ignimbrites and the Tuff Anthracifères of the Massif Central, which are also subaerial, sub-alkaline dacitic to rhyolitic ignimbrites (Delfour, 1989;Schneider et al, 1989;Lardeaux et al, 2014). The latter have been dated in two basins of the Massif Central using the U-Pb zircon ID-TIMS method and have yielded UPb dates of c. 332 -333 Ma (Bruguier et al, 1998;Fig. 9B).…”

Section: Possible Locations Of the Source Volcanoesmentioning

confidence: 99%

Geochemistry and origin of Carboniferous (Mississippian; Viséan) bentonites in the Namur-Dinant Basin, Belgium: evidence for a Variscan volcanic source

Pointon¹,

Chew²,

Delcambre³

et al. 2018

Geol. Belg.

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ABSTRACT. Several thin clay-rich horizons occur interbedded with Mississippian (Viséan) limestones in the Namur-Dinant Basin, southern Belgium. These have been interpreted as diagenetically altered volcanic ash layers (bentonites). Whole-rock geochemical analysis of several bentonites was undertaken to provide insight into their original magmatic composition. Ratios of several trace elements that are considered to be immobile during diagenetic alteration and indicators of petrogenetic processes suggest that most of the bentonites were originally trachyandesitic to trachytic ashes. Furthermore, the coarse grain size of euhedral zircon phenocrysts (up to 400 µm in length) suggests a proximal volcanic source. Zircon U-Pb isotopic ages and wholerock geochemical data from these bentonites were compared with literature data from volcanic and intrusive rocks in adjacent areas, and suggest that the bentonites were sourced from volcanoes within the Variscan orogenic belt.KEYWORDS: altered volcanic ash, cinerite, whole-rock geochemistry, trace element geochemistry, X-ray diffraction analysis.http://dx

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“…Therefore, the only Proterozoic component of the zircon age spectrum that cannot be readily matched with a source in the Variscides is that found at c. 1600 Ma. It is also possible to find a Variscan source for the zircons dated as 390-396 Ma, since this corresponds to the subduction-obduction cycle of the Rheic and Galicia-Massif Central Palaeozoic oceans (Matte, 1986); furthermore, grains of this age have been found in the Visean of the Massif Central (Bruguier et al 1998).…”

Section: Discussionmentioning

confidence: 96%

“…High-grade paragneisses in the Mid-German Crystalline Rise (adjacent to the Saxo-Thuringian Zone) contain small numbers of c. 1.0 Ga zircons in association with dominant c. 550 Ma and c. 2.06 Ga zircons (Zeh et al 2001). In the Massif Central of France, Visean volcanic rocks contain xenocrystic zircons dated as Mesoproterozoic, > 1.0 Ga (Bruguier et al 1998), approximately coeval with the late Mesoproterozoic to early Neoproterozoic group in the Canonbie Bridge Sandstone Formation. Therefore, there is evidence to indicate that late Mesoproterozoic to early Neoproterozoic zircons could have been derived from basement rocks in the Variscides.…”

Section: Discussionmentioning

confidence: 99%

Variscan sourcing of Westphalian (Pennsylvanian) sandstones in the Canonbie Coalfield, UK

Morton

Jones

2010

Geol. Mag.

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-The zircon age spectrum in a sample from the Canonbie Bridge Sandstone Formation (Asturian) of southern Scotland contains two main peaks. One is Early Carboniferous in age (348-318 Ma), and corresponds to the age of igneous activity during the Variscan Orogeny. The other is of late Neoproterozoic to early Cambrian age (693-523 Ma), corresponding to the Cadomian. Together, these two groups comprise 70 % of the zircon population. The presence of these two peaks shows unequivocally that a significant proportion of the sediment was derived from the Variscides of western or central Europe. The zircon population also contains a range of older Proterozoic zircons and a small Devonian component. These could have been derived from the Variscides, but it is possible that some were locally derived through recycling of northerly derived sandstones of Devonian-Carboniferous age. The zircon age data confirm previous suggestions of Variscide sourcing to the Canonbie area, made on the basis of petrographical, heavy mineral and palaeocurrent evidence, and extend the known northward distribution of Variscan-derived Westphalian sediment in the UK.

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Late Visean hidden basins in the internal zones of the Variscan belt: U-Pb zircon evidence from the French Massif Central

Cited by 39 publications

References 16 publications

Late Visean thermal event in the northern part of the French Massif Central: new 40Ar/39Ar and Rb–Sr isotopic constraints on the Hercynian syn-orogenic extension

Late Visean thermal event in the northern part of the French Massif Central: new 40Ar/39Ar and Rb–Sr isotopic constraints on the Hercynian syn-orogenic extension

Geochemistry and origin of Carboniferous (Mississippian; Viséan) bentonites in the Namur-Dinant Basin, Belgium: evidence for a Variscan volcanic source

Variscan sourcing of Westphalian (Pennsylvanian) sandstones in the Canonbie Coalfield, UK

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