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

Content Provider	Springer Nature Link
Author	Laurent, Oscar Couzinié, Simon Zeh, Armin Vanderhaeghe, Olivier Moyen, Jean François Villaros, Arnaud Gardien, Véronique Chelle Michou, Cyril
Copyright Year	2017
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.
Starting Page	421
Ending Page	451
Page Count	31
File Format	PDF
ISSN	14373254
Journal	International Journal of Earth Sciences
Volume Number	106
Issue Number	2
e-ISSN	14373262
Language	English
Publisher	Springer Berlin Heidelberg
Publisher Date	2017-01-06
Publisher Place	Berlin, Heidelberg
Access Restriction	One Nation One Subscription (ONOS)
Subject Keyword	U–Pb dating Zircon French Massif Central Granitoids Vaugnerites Variscan orogeny Geology Geophysics/Geodesy Sedimentology Structural Geology Mineral Resources Geochemistry
Content Type	Text
Resource Type	Article
Subject	Earth and Planetary Sciences

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