An Ordovician basalt to peralkaline rhyolite fractionation series from Avoca, Ireland

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doi: 10.1144/gsjgs.148.4.0711
Authors:McConnell, B. J.; Stillman, C. J.; Hertogen, J.
Author Affiliations:Primary:
Trinity College, Department of Geology, Dublin, Ireland
University of Leuven, Belgium
University of Liverpool, United Kingdom
Volume Title:Journal of the Geological Society of London
Source:Journal of the Geological Society of London, Vol.148 (Part 4), p.711-718. Publisher: Geological Society of London, London, United Kingdom. ISSN: 0016-7649
Publication Date:1991
Note:In English. 49 refs.; illus. incl. 1 table, geol. sketch map
Summary:The Upper Ordovician Avoca volcanic rocks host a Kuroko-type massive sulphide deposit. Immobile-element geochemistry of the lavas shows a bimodal subdivision into acid and basic groups; basalts are interpreted as products of the rifting of a volcanic arc, whereas the rhyolites are highly enriched in HFS elements and were originally peralkaline. Constant incompatible element ratios throughout the compositional spectrum indicate a fractional crystallization relationship between the basic and acid members. The basaltic magmas evolved by crystallization of plagioclase, producing large negative Eu anomalies. The transition to peralkalinity is marked by LREE depletion and no further increase in the Eu anomaly. A group of acidpyroclastic Avoca rocks are subalkaline and are probably unrelated to the main evolutionary series. The Avoca volcanic series was erupted in an extensional tectonic setting within a continental margin volcanic arc, similar to the contemporaneous Welsh marginal basin. [R.A.H.]
Subjects:Basalts; Crystal fractionation; Igneous rocks; Magmas; Major elements; Metals; Ordovician; Paleozoic; Peralkalic composition; Rare earths; Rhyolites; Trace elements; Upper Ordovician; Volcanic rocks; Europe; Ireland; Western Europe; Wicklow Ireland; Avoca Ireland
Coordinates:N524000 N531500 W0060000 W0064500
Abstract Numbers:91M/3448
Record ID:1993027653
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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