Crustal controls on the genesis of the 400 Ma old Caledonian granites

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doi: 10.1016/0031-9201(84)90036-0
Authors:Halliday, A. N.; Stephens, W. E.
Author Affiliations:Primary:
Scot. Univ., Res. and React. Cent., Glasgow, United Kingdom
Univ. Clermont II, Dep. Geol., France
Univ. St. Andrews, Dep. Geol., United Kingdom
Volume Title:Granitoids
Volume Authors:Allègre, Claude J., editor; Didier, Jean
Source:Physics of the Earth and Planetary Interiors, 35(1-3), p.89-104; Symposium to honor Maurice Roques ; Granitoids, Clermont-Ferrand, France, 1984, Claude J. Allègre and Jean Didier. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0031-9201
Publication Date:1984
Note:In English. 93 refs.; illus. incl. sketch map
Summary:The approx 400 m.y. Caledonian granitic rocks of the British Isles form a high-K calc-alkaline suite with low K/Na compared with European Hercynian or Australian Caledonian granites. Granites south of the Iapetus suture are largely S-types and occur within thick geosynclinal prisms of Lower Palaeozoic flysch. The granitic rocks north of the Iapetus suture are largely I-types with high Ba and Sr, with evidence of a significant component of continental crust. The overall isotopic features show similarities with Lower Palaeozoic sediments, because both represent averages of the available crust plus material derived from the mantle. Available data are compatible with only a small amount of Lewisian material incorporated in the magmas, and most of the crust involved was of late Precambrian or Lower Palaeozoic age. The high Sr characteristics of the British 400 m.y. granitic rocks (a feature generally coupled with absence of a major Eu anomaly) is best explained by melting of a feldspar- absent source which had not gone through a previous feldspar fractionation cycle. This is compatible with a mainly mantle source, and/or lower crust without an upper crustal history. The existence of a chemical province within the British Caledonian precludes the possibility that the granites have been brought into their present positions by large sinistral movements. The high Na nature of the province is not due to more extensive sea-water metasomatism in the source. [D.A.C.M.]
Subjects:Alkaline earth metals; Caledonian Orogeny; Controls; Crust; Differentiation; Emplacement; Fractional crystallization; Genesis; Geosynclines; Granites; Igneous rocks; Isotopes; Lead; Magmas; Mantle; Melting; Metals; Paleozoic; Pb-206/Pb-204; Pb-207/Pb-204; Petrology; Plutonic rocks; Pollution; Radioactive isotopes; Sr-87/Sr-86; Stable isotopes; Strontium; Europe; Great Britain; United Kingdom; Western Europe; Evolution; Ratios
Abstract Numbers:85M/4634
Record ID:1985048457
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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