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Combined Sm-Nd and Rb-Sr isotope systematics in the Donegal granitoids and their petrogenetic implications

Published online by Cambridge University Press:  01 May 2009

C. S. Dempsey ,
A. N. Halliday  and
I. G. Meighan
C. S. Dempsey
Affiliation:
Department of Geology, The Queen's University of Belfast, Belfast BT7 1NN, U.K.
A. N. Halliday
Affiliation:
Isotope Geology Unit, Scottish Universities Research and Reactor Centre, East Kilbride, Glasgow G75 0QU, U.K.
I. G. Meighan
Affiliation:
Department of Geology, The Queen's University of Belfast, Belfast BT7 1NN, U.K.
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Abstract

The metaluminous to peraluminous granitoids of the Donegal batholith, northwest Ireland, were emplaced at c. 400 Ma into greenschist-amphibolite facies metasediments of the Dalradian Supergroup. Sm-Nd and Rb-Sr isotopic data are provided for eleven granitoid samples from six of the plutons and one specimen from the northeast granodiorite pluton of the Newry complex, Co. Down; the Donegal results reveal essentially similar initial Sr isotope ratios (0.7051–0.7068) but highly variable initial eNd values, −1.2 to −8.3 (and −0.5 for Newry). Certain granitoids have distinctive Nd isotopic compositions characteristic of the involvement of old, LREE-enriched continental crust in some cases or young crust and/or mantle-derived magmas in others. The Nd and Sr isotopic variations can be explained by a variety of mixing hypotheses.

Type
Articles
Information
Geological Magazine , Volume 127 , Issue 1 , January 1990 , pp. 75 - 80
Copyright
Copyright © Cambridge University Press 1990

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