Chemical variation in Hercynian basalts relative to plate tectonics

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doi: 10.1144/gsjgs.139.4.0505
Authors:Floyd, P. A.
Author Affiliations:Primary:
Univ. Keele, Dep. Geol., Keele, Staffs. ST5 5BG, United Kingdom
Volume Title:Journal of the Geological Society of London
Source:Journal of the Geological Society of London, 139(4), p.505-520. Publisher: Geological Society of London, London, United Kingdom. ISSN: 0016-7649
Publication Date:1982
Note:In English. 3 p. refs.Including thematic set of papers on Plate tectonics and the evolution of the British Isles; illus. incl. 2 tables, sketch map
Summary:Geochemically, Hercynian basalts have: 1) relative enrichment in incompatible elements, 2) fractionated REE patterns ranging from mildly to strongly light REE-enriched and 3) generally low LIL/high field strength (HFS) element ratios. They are predominantly tholeiites, though with some alkali basalts at trough margins. Basalts from different sedimentary troughs within the main Hercynian tectonic zones are characterized by specific incompatible element abundances and ratios. These variations are interpreted in terms of variable fractional crystallization, partial melting and mantle heterogeneity. Two systematic chemical changes have been recognized throughout the Devonian and Carboniferous, with both light/heavy REE and LIL/HFS element ratios increasing with time. These features may be related to the introduction of LIL-enriched fluids derived by dehydration of subducted lithosphere which caused progressive metasomatism of the overlying mantle wedge. [R.A.H.]
Subjects:Alkali basalts; Basalts; Carboniferous; Continental drift; Devonian; Differentiation; Fractional crystallization; Geochemistry; Heterogeneity; Igneous rocks; Magmas; Major elements; Mantle; Metals; Metasomatism; Moldanubian; Paleozoic; Partial melting; Permian; Petrology; Plate tectonics; Rare earths; Stratigraphy; Tectonophysics; Tholeiitic basalt; Trace elements; Volcanic rocks; England; Europe; Great Britain; South-West England; United Kingdom; Variscides; Western Europe; Rheno-Hercynian Zone; Saxo-Thuringian Zone
Abstract Numbers:83M/0515
Record ID:1983055890
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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