Ordovician intrusions of the Strumble Head-Mynydd Preseli region, Wales; lateral extensions of the Fishguard volcanic complex

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doi: 10.1144/gsjgs.146.1.0113
Authors:Bevins, R. E.; Lees, G. J.; Roach, R. A.
Author Affiliations:Primary:
Natl. Mus. Wales, Dep. Geol., Cardiff, United Kingdom
Other:
Univ. Keele, United Kingdom
Volume Title:Journal of the Geological Society of London
Source:Journal of the Geological Society of London, 146(1), p.113-123. Publisher: Geological Society of London, London, United Kingdom. ISSN: 0016-7649
Publication Date:1989
Note:In English. 35 refs.; illus. incl. 2 tables, geol. sketch map
Summary:New geochemical data, combined with petrographic analyses, indicate that a major doleritic and gabbroic sill complex with minor microtonalitic components which cuts Ordovician strata to the E of Fishguard, represent an eastward extension of the Ordovician (Llanvirn) Fishguard volcanic complex lavas and high- level intrusions of the Strumble Head region. Similar doleritic intrusions crop out to the W of Strumble Head as far as Traeth Llynfn. The data confirm that the Fishguard volcanic complex has tholeiitic affinities and that compositional variations largely result from low-P fractional crystallization. Incompatible element discriminant diagrams indicate that the parental basic magmas were derived by melting of a slightly depleted mantle source similar to N-Type MORB, to which had been added a minor supra-subduction zone LIL element composition. The data are consistent with emplacement of the magmas in a marginal basin environment. [R.A.H.]
Subjects:Diabase; Diorites; Fractional crystallization; Gabbros; Geochemistry; Igneous rocks; Intrusions; Llanvirnian; Middle Ordovician; Ordovician; Paleozoic; Petrology; Plutonic rocks; Rhyolites; Sills; Stratigraphy; Tonalite; Volcanic rocks; Europe; Great Britain; United Kingdom; Wales; Welsh Basin; Western Europe; Fishguard Volcanic Complex; Mynydd Preseli region; Strumble Head region
Abstract Numbers:89M/4938
Record ID:1989062427
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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