Lead isotopic composition of Hercynian granitic K-feldspars constrains continental genesis

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Authors:Vitrac, A. M.; Albarede, F.; Allegre, C. J.
Author Affiliations:Primary:
Inst. phys. globe, Paris 75230, France
Volume Title:Nature (London)
Source:Nature (London), 291(5815), p.460-464. Publisher: Macmillan Journals, London, United Kingdom. ISSN: 0028-0836
Publication Date:1981
Note:In English. 60 refs.; illus. incl. 2 tables
Summary:Lead isotopic compositions have been determined in many K-feldspars from granitic rocks emplaced during the Variscan (Hercynian) orogeny sensu lato (around 300 m.y.) in various parts of Europe and the eastern US. The ratios show a regular geographical pattern with mu contours arched around S France and parallel to the Atlantic coast of the US. This distribution parallels predrift palaeogeographical zones during the Palaeozoic. The Pb-isotope pattern of Variscan granitic rocks is similar to that of some orogenic volcanic suites but is better explained by crustal melting than by a Hercynian mantle-crust material mixing. The continental crust from these areas must be older than 3000 m.y. Large-scale fluid circulation in the crust during orogenic processes apparently explains the observed geographical patterns of Pb isotopes. (Authors' abstract) [T.R.]
Subjects:Alkali feldspar; Continental crust; Crust; Feldspar group; Framework silicates; Geochemistry; Granites; Igneous rocks; Isotopes; K-feldspar; Lead; Mechanism; Metals; Orogeny; Pb-206/Pb-204; Pb-207/Pb-204; Pb-208/Pb-204; Plutonic rocks; Radioactive isotopes; Silicates; Stable isotopes; Variscan Orogeny; Africa; Appalachians; Armorican Massif; Central Massif; Corsica; Europe; France; Iberian Peninsula; Morocco; North Africa; North America; Pyrenees; Southern Europe; Spain; Vosges Mountains; Western Europe; Ratios; Remobilization
Abstract Numbers:83M/0516
Record ID:1982052881
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom, Reference includes data from PASCAL, Institute de l'Information Scientifique et Technique
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