Sources of Hercynian granitoids from the French Massif Central: Inferences from Nd isotopes and consequences for crustal evolution

Pin, Christian; Duthou, Jean-Louis

doi:10.1016/0009-2541(90)90285-f

Cited by 98 publications

(65 citation statements)

References 54 publications

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“…Therefore the high-T Hercynian metamorphism did not completely destroy any heterogeneities. The preservation of Sm-Nd isotopic heterogeneity in zircons subjected to magmatic temperatures has also been noted by Paterson et al [1992]. Second, the presence of isotopic heterogeneity on a centimeter scale is on the same scale (centimeters) as that found in the mesosome·leucosome pairs in the migmatites; such a scale is common scale for granulitic terrains [Burton and O'Nions, 1990;McCulloch and Black, 1984].…”

Section: Premetamorphic Peak Granitoidsmentioning

confidence: 57%

“…Watson and Harrison [1983] state that at H20 contents above 2 wt %, zircon solubility in melts is independent of the water content, whereas highly undersaturated granitic melts with 0.2 wt % H20 dissolve 30-40% less zircon than a water saturated one. Pichavant et al [1992] found differences of 1 order of magnitude in P diffusion coefficient in apatite between water-saturated (6 wt % H20) and water-undersaturated conditions, although no great change in P apatite/melt interface concentration was observed between the two experiments. The water content of the ACT anatectic melts is likely to have been high only at the beginning of the melting process, becoming stable at values of around 2-3 wt % H20, typical of melts generated by fluid-absent biotite dehydration melting at the conditions estimated in the area [Clemens aru1 Vielzeuf, 1987].…”

Section: ----------------mentioning

confidence: 96%

“…A detailed discussion of the petrography, mineral chemistry and petrogenesis of these granitoids is given by Barbero and Villaseca [1992] and Barbero [1992]. These granites plot in the quartz rich fields of the modal QAP diagram [Barbero and Villaseca, 1992, Figure 3].…”

Section: Layos Restite-rich Granitesmentioning

confidence: 99%

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Geochemical and isotopic disequilibrium in crustal melting: An insight from the anatectic granitoids from Toledo, Spain

Barbero¹,

Villaseca²,

Rogers³

et al. 1995

J. Geophys. Res.

106

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Abstract. In the Hercynian Anatectic Complex of Toledo (ACT) the anatectic granitoids include leucogranitic leucosomes, leucogranitic massifs, and restite-rich granites. They show a broad range of initial Sr and Nd isotope ratios from 0.71 I to 0.720 and 0.51164 to 0.51203, respectively, which clearly indicate the absence of isotopic homogenization in the melts. Broadly, the ranges reflect the isotopic variation of the metapelitic protoliths. If crusta! melting occurs under water-undersaturated conditions, as is the case of the ACT, the generated melts do not isotopically and chemically equilibrate with the granulitic residuum. The preservation of heterogeneities could arise through a number of pmcesses. (1) duration of the process:in which the presence of melts with disequilibrium features, and the high solid content of several of the granites in the ACT point to a very short-lived magmatic system, (2) limited

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Section: Premetamorphic Peak Granitoidsmentioning

confidence: 57%

Section: ----------------mentioning

confidence: 96%

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Geochemical and isotopic disequilibrium in crustal melting: An insight from the anatectic granitoids from Toledo, Spain

Barbero¹,

Villaseca²,

Rogers³

et al. 1995

J. Geophys. Res.

106

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“…Post-thickening crustal melting responsible for Variscan magmatism and hightemperature regional metamorphism in the Cévennes area is geologically well documented (Duthou et al, 1984, Ledru et al, 1989, Pin and Duthou, 1990, Montel et al, 1992, Faure et al, 2001and Faure et al, 2002.…”

Section: Discussionmentioning

confidence: 99%

Electron microprobe monazite geochronology of magmatic events: Examples from Variscan migmatites and granitoids, Massif Central, France

Mézème

Cocherie

Faure³

et al. 2006

Lithos

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To cite this version:Eugène Abstract U-Th-Pb dating of monazite with the electron probe microanalyser (EPMA) is increasingly documented as a reliable geochronological method offering high spatial resolution. This method has been applied on monazite from the Cévennes migmatites and granitoids from the southeast of the French Massif Central. Measurements were performed on separated grains after systematic back-scattered electron (BSE) imaging. Monazites from migmatites record two main ages: (i) a protolith age of about 550-543 Ma obtained on inherited cores, and (ii) a migmatization event between 329 ± 5 and 323 ± 3 Ma recorded by monazite rims and all other monogenetic grains. Monazite from the peraluminous Rocles pluton yields a 318 ± 3 Ma age. Finally, three granite dykes are dated at 333 ± 6, 318 ± 5 and 311 ± 5 Ma; the older dyke is the most deformed of them and is interpreted as linked to the migmatization event; the two other dykes are geochronologically, petrologically and structurally coeval with the Rocles pluton. The data constrain the timing of crustal melting following Variscan thickening in the northern Cévennes area. Migmatization of Ordovician protoliths took place at 329-323 Ma and was shortly followed by intrusion of leucogranite at 318-311 Ma. The study shows that EPMA dating of monazite can be successfully used to resolve a close succession of regional melting events.

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“…These authors propose that the gabbro-norite rocks, although having a primitive character, show Sr-Nd isotope composition (Sr i =0.7049-0.7053, ε Nd =−2.1 to −2.5) suggesting the existence of a sub-Iberian enriched mantle during the Variscan event. The enriched nature of subcontinental mantle domains is also present in other sectors within the Variscan Belt (Fernández-Suárez et al, 2011;Janousek et al, 2000;Moreno-Ventas et al, 1995;Orejana et al, 2009;Pin and Duthou, 1990;Villaseca et al, 2011). Further constraints about the hybridisation process in the genesis of granitoids are given by the presence of mafic microgranular enclaves associated with granitic rocks, as they are generally considered as representing a mantle-derived component (Barbarin and Didier, 1992;Bea et al, 1999;Bonin, 2004;Cocherie et al, 1994;Collins et al, 2000;Dias and Leterrier, 1994;Dias et al, 2002;Didier, 1987;Janousek et al, 2004;Moreno-Ventas et al, 1995;Orsini et al, 1991;Renna et al, 2006;Silva and Neiva, 2004;Slaby and Martin, 2008;Vernon, 1984).…”

Section: Nature Of the Granite Sourcesmentioning

confidence: 99%

Late-Variscan emplacement and genesis of the Vieira do Minho composite pluton, Central Iberian Zone: Constraints from U–Pb zircon geochronology, AMS data and Sr–Nd–O isotope geochemistry

Martins

Ovaia

Noronha

2013

Lithos

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In the Central Iberian Zone synorogenic (syn-and late-D 3 , the last deformation phase) composite batholiths of biotite-rich granitods with peraluminous character are well represented. We report here U-Pb zircon and monazite ages, geochemical, Sr-Nd-O isotopic data and Anisotropy of Magnetic Susceptibility (AMS) studies for the late-D 3 Vieira do Minho pluton, in northern Portugal. AMS reveals the paramagnetic behaviour of these granites and the magnetic fabric enhances the major role of NW-SE regional anisotropies on controlling the ascent and emplacement of the magmas. Magnetic anisotropy and medium temperature microstructures also point out the evolution of regional tectonics during crystallization of the magma. U-Pb zircon and monazite analyses yield consistent ages of 310 ± 2 Ma and 312 ± 2 Ma, interpreted as emplacement age. The Vieira do Minho pluton consists of two peraluminous monzogranites, the VMG and the MRG. Both have similar ε Nd values (VMG= −5.2 to −5.7; MRG =−4.98 to −5.96) but the VMG is slightly enriched in 87 Sr/ 86 i = 0.7087-0.7098 as well as in δ 18 O in the range of 10.6‰ to 11.0‰ than the MRG with 87 Sr/ 86 i =0.7064-0.7075 and δ 18 O=9.9‰-10.5‰. These granites are associated with coeval scarce grabroic intrusions and/or mafic microgranular enclaves which are not considered as mafic precursors of the associated granitic magmatism. Instead, a lower metaigneous crustal source, at different levels, is proposed based on the available data set.

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Sources of Hercynian granitoids from the French Massif Central: Inferences from Nd isotopes and consequences for crustal evolution

Cited by 98 publications

References 54 publications

Geochemical and isotopic disequilibrium in crustal melting: An insight from the anatectic granitoids from Toledo, Spain

Geochemical and isotopic disequilibrium in crustal melting: An insight from the anatectic granitoids from Toledo, Spain

Electron microprobe monazite geochronology of magmatic events: Examples from Variscan migmatites and granitoids, Massif Central, France

Late-Variscan emplacement and genesis of the Vieira do Minho composite pluton, Central Iberian Zone: Constraints from U–Pb zircon geochronology, AMS data and Sr–Nd–O isotope geochemistry

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