Rb-Sr isochron study of the Thorr and Main Donegal Granites, Ireland

Autor: P. J. O'Connor, J. C. Roddick, Alex N. Halliday, M. D. Max, C. B. Long, P. S. Kennan
Rok vydání: 2007
Předmět:
Zdroj: Geological Journal. 17:279-295
ISSN: 1099-1034
0072-1050
DOI: 10.1002/gj.3350170403
Popis: A Rb-Sr whole-rock isochron study indicates that the entire Donegal granite suite was emplaced into orthotectonic Caledonian (Dalradian) rocks over a short interval during mid-Silurian to earliest-Devonian times. The Thorr pluton, probably the earliest member of the suite, yields an age of 418 ± 26 Myr and initial 87Sr/86Sr ratio of 0·7055 ± 4, while the latest member, the Main Donegal pluton has an age of 407 ± 23 Myr and initial 87Sr/86Sr ratio of 0·7063 ± 5 (Λ87Rb = 1·42 ± 10−11 yr−1). Errors on both the age and initial Sr isotope ratios incorporate both a priori and geological scatter components and are quoted at the 2-sigma level. The low and restricted range of initial Sr isotope ratios suggests small but significant differences in the composition of the parental granitic magmas which were derived from a low Rb/Sr, low 87Sr/86Sr source.
Databáze: OpenAIRE
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