Ordovician bimodal volcanism in SW Wales; geochemical evidence for petrogenesis of the silicic rocks

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doi: 10.1144/gsjgs.148.4.0719
Authors:Bevins, R. E.; Lees, G. J.; Roach, R. A.
Author Affiliations:Primary:
National Museum of Wales, Department of Geology, Cardiff, United Kingdom
Other:
University of Keele, United Kingdom
Volume Title:Journal of the Geological Society of London
Source:Journal of the Geological Society of London, Vol.148 (Part 4), p.719-729. Publisher: Geological Society of London, London, United Kingdom. ISSN: 0016-7649
Publication Date:1991
Note:In English. 37 refs.; illus. incl. 2 tables, geol. sketch map
Summary:Rhyolitic lavas, pyroclastic rocks and high-level intrusions are an important constituent of a bimodal tholeiitic basalt-rhyolite association of Llanvirn age exposed in N Pembrokeshire, Ramsey Island, the Fishguard area and on Mynydd Preseli. In the same region, a 400 m thick tholeiitic layered differentiated sill, the St David's Head intrusion, considered to be cogenetic, comprises a series of units ranging from basic, through intermediate to acidic composition. Analyses for major, trace and REE in these various units are reported and suggest that they are related via a crystal fractionation process. [R.A.H.]
Subjects:Basalts; Calc-alkalic composition; Crystal fractionation; Gabbros; Igneous rocks; Lava; Lower Ordovician; Mafic composition; Magmas; Major elements; Ordovician; Paleozoic; Plutonic rocks; Rhyolites; Siliceous composition; Tholeiitic composition; Trace elements; Volcanic rocks; Volcanism; Volcanology; Europe; Great Britain; Pembrokeshire Wales; United Kingdom; Wales; Western Europe; Dyfed Wales
Coordinates:N513500 N520500 W0043000 W0051500
Abstract Numbers:92M/0616
Record ID:1993027654
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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