International Journal of Earth Sciences

, Volume 106, Issue 2, pp 421–451

Protracted, coeval crust and mantle melting during Variscan late-orogenic evolution: U–Pb dating in the eastern French Massif Central

  • Oscar Laurent
  • Simon Couzinié
  • Armin Zeh
  • Olivier Vanderhaeghe
  • Jean-François Moyen
  • Arnaud Villaros
  • Véronique Gardien
  • Cyril Chelle-Michou
Original Paper

DOI: 10.1007/s00531-016-1434-9

Cite this article as:
Laurent, O., Couzinié, S., Zeh, A. et al. Int J Earth Sci (Geol Rundsch) (2017) 106: 421. doi:10.1007/s00531-016-1434-9

Abstract

The late stages of the Variscan orogeny are characterized by middle to lower crustal melting and intrusion of voluminous granitoids throughout the belt, which makes it akin to “hot” orogens. These processes resulted in the development of large granite–migmatite complexes, the largest of which being the 305–300-Ma-old Velay dome in the eastern French Massif Central (FMC). This area also hosts a wide range of late-Variscan plutonic rocks that can be subdivided into four groups: (i) cordierite-bearing peraluminous granites (CPG); (ii) muscovite-bearing peraluminous granites (MPG); (iii) K-feldspar porphyritic, calc-alkaline granitoids (KCG) and (iv) Mg–K-rich (monzo)diorites and lamprophyres (“vaugnerites”). New results of LA-SF-ICP-MS U–Pb zircon and monazite dating on 33 samples from all groups indicate that both granites and mafic rocks emplaced together over a long period of ~40 million years throughout the Carboniferous, as shown by intrusion ages between 337.4 ± 1.0 and 298.9 ± 1.8 Ma for the granitoids, and between 335.7 ± 2.1 and 299.1 ± 1.3 Ma for the vaugnerites. Low zircon saturation temperatures and abundant inherited zircons with predominant late Ediacaran to early Cambrian ages indicate that the CPG and MPG formed through muscovite or biotite dehydration melting of ortho- and paragneisses from the Lower Gneiss Unit. The KCG and vaugnerites contain very few inherited zircons, if any, suggesting higher magma temperatures and consistent with a metasomatized lithospheric mantle source for the vaugnerites. The KCG can be explained by interactions between the CPG/MPG and the vaugnerites, or extensive differentiation of the latter. The new dataset provides clear evidence that the eastern FMC was affected by a long-lived magmatic episode characterized by coeval melting of both crustal and mantle sources. This feature is suggested here to result from a lithospheric-scale thermal anomaly, triggered by the removal of the lithospheric mantle root. The spatial distribution of the dated samples points to a progressive southward delamination of the lithospheric mantle, perhaps in response to rollback following continental subduction, or to “retro-delamination” owing to the retreat of a south-verging subduction zone.

Keywords

U–Pb dating Zircon French Massif Central Granitoids Vaugnerites Variscan orogeny 

Supplementary material

531_2016_1434_MOESM1_ESM.pdf (8.1 mb)
Supplementary material 1 (PDF 8257 kb)
531_2016_1434_MOESM2_ESM.xlsx (1009 kb)
Supplementary material 2 (XLSX 1008 kb)
531_2016_1434_MOESM3_ESM.xlsx (368 kb)
Supplementary material 3 (XLSX 368 kb)

Copyright information

© Springer-Verlag Berlin Heidelberg 2017

Authors and Affiliations

  • Oscar Laurent
    • 1
    • 2
    • 12
  • Simon Couzinié
    • 3
    • 4
  • Armin Zeh
    • 1
    • 5
  • Olivier Vanderhaeghe
    • 6
  • Jean-François Moyen
    • 3
  • Arnaud Villaros
    • 7
    • 8
    • 9
  • Véronique Gardien
    • 10
  • Cyril Chelle-Michou
    • 3
    • 11
  1. 1.Institut für GeowissenschaftenJ.W. Goethe UniversitätFrankfurt Am MainGermany
  2. 2.Département de Géologie B20Université de LiègeLiègeBelgium
  3. 3.Département de GéologieUniversité Jean MonnetSaint-ÉtienneFrance
  4. 4.Department of Earth SciencesUniversity of StellenboschMatielandSouth Africa
  5. 5.Abteilung Mineralogie und Petrologie, Institut für Angewandte GeowissenschaftenKarlsruher Institut für Technologie, Campus SüdKarlsruheGermany
  6. 6.Géosciences Environnement ToulouseUniversité Paul SabatierToulouseFrance
  7. 7.Université d’Orléans, ISTO, UMR 7327OrléansFrance
  8. 8.CNRS, ISTO, UMR 7327OrléansFrance
  9. 9.BRGM, ISTO, UMR 7327OrléansFrance
  10. 10.LGL, TPE UMR5276Université Lyon 1LyonFrance
  11. 11.Department of Earth SciencesUniversity of GenevaGenevaSwitzerland
  12. 12.Institute for Geochemistry and PetrologyETH ZürichZurichSwitzerland