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
Other:
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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100 1 |a McConnell, B. J.  |e analytic author  |u Trinity College, Department of Geology, Dublin 
245 1 3 |a An Ordovician basalt to peralkaline rhyolite fractionation series from Avoca, Ireland 
300 |a p. 711-718 
500 |a In English. 49 refs. 
500 |a Abstract number: 91M/3448 
500 |a Abstractor: R.A.H. 
500 |a Affiliation: Trinity College, Department of Geology; Dublin; IRL; Ireland 
500 |a Affiliation: University of Leuven; ; BEL; Belgium 
500 |a Affiliation: University of Liverpool; ; GBR; United Kingdom 
500 |a Key title: Journal of the Geological Society of London 
500 |a Source note: 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 
500 |a Publication type: journal article 
504 |b 49 refs. 
510 3 |a GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom 
520 |a 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. 
650 7 |a Basalts  |2 georeft 
650 7 |a Crystal fractionation  |2 georeft 
650 7 |a Igneous rocks  |2 georeft 
650 7 |a Magmas  |2 georeft 
650 7 |a Major elements  |2 georeft 
650 7 |a Metals  |2 georeft 
650 7 |a Ordovician  |2 georeft 
650 7 |a Paleozoic  |2 georeft 
650 7 |a Peralkalic composition  |2 georeft 
650 7 |a Rare earths  |2 georeft 
650 7 |a Rhyolites  |2 georeft 
650 7 |a Trace elements  |2 georeft 
650 7 |a Upper Ordovician  |2 georeft 
650 7 |a Volcanic rocks  |2 georeft 
651 7 |a Europe  |2 georeft 
651 7 |a Ireland  |2 georeft 
651 7 |a Western Europe  |2 georeft 
651 7 |a Wicklow Ireland  |2 georeft 
653 |a Avoca Ireland 
700 1 |a Stillman, C. J.,  |e analytic author  |u University of Leuven 
700 1 |a Hertogen, J.,  |e analytic author  |u University of Liverpool 
773 0 |t Journal of the Geological Society of London  |d London : Geological Society of London, Jul. 1991  |x 0016-7649  |y JGSLAS  |n 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 type: journal article  |g Vol. 148 , Part 4  |h illus. incl. 1 table, geol. sketch map 
856 |u urn:doi: 10.1144/gsjgs.148.4.0711