Isotopic and trace-element arguments for the lower-crustal origin of Hercynian granitoids and pre-Hercynian orthogneisses, Massif Central (France)

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doi: 10.1016/0009-2541(88)90027-7
Authors:Downes, Hilary; Duthou, Jean-Louis
Author Affiliations:Primary:
Birkbeck Coll., Dep. Geol., London, United Kingdom
CNRS, France
Volume Title:Chemical Geology
Source:Chemical Geology, 68(3-4), p.291-308. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0009-2541
Publication Date:1988
Note:In English. 44 refs.; illus. incl. 3 tables, sketch map
Summary:The Cadomian-Hercynian basement of the Massif Central contains both pre-metamorphic orthogneisses (600-410 m.y.) and post-metamorphic undeformed granitic rocks (360-275 m.y.). Major-, trace-element and Sr, Nd isotopic analyses of these intrusions indicate slight differences in source material for orthogneisses and two types of undeformed granitic rock: granodiorite/monzogranites, and evolved leucogranites. The two types are compared, and it is concluded that the source of the orthogneisses is dominated by a lower-crustal metasedimentary source. Granodiorites/monzogranites form the least evolved end-members of a series trending to highly-evolved leucogranites. Granodiorites and monzogranite have epsilont,nd between -6.5 and -3.4 and epsilont,sr values <+ 100. These values are similar to those of meta-igneous and some metasedimentary lower-crustal xenoliths and thus the granodiorites/monzogranites may have been derived from a mixture of these two components with the meta-igneous component dominating. [P.Br.]
Subjects:Alkaline earth metals; Analysis; Crust; Genesis; Geochemistry; Gneisses; Granites; Granodiorites; Igneous rocks; Inclusions; Intrusions; Isotopes; Lower crust; Major elements; Metals; Metamorphic rocks; Monzogranite; Nd-144/Nd-143; Neodymium; Orthogneiss; Plutonic rocks; Rare earths; Sr-87/Sr-86; Stable isotopes; Strontium; Trace elements; Variscan Orogeny; Xenoliths; Central Massif; Europe; France; Western Europe
Abstract Numbers:89M/1967
Record ID:1988047785
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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