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Trondhjemitic and granitic melts formed by fractional crystallization of an olivine tholeiite from Reykjanes Peninsula, Iceland

Published online by Cambridge University Press:  10 October 2005

E. MARTIN  and
O. SIGMARSSON
E. MARTIN
Affiliation:
Laboratoire Magmas et Volcans, OPGC – Université Blaise Pascal – CNRS, 5 rue Kessler, 63038 Clermont-Ferrand, France
O. SIGMARSSON
Affiliation:
Laboratoire Magmas et Volcans, OPGC – Université Blaise Pascal – CNRS, 5 rue Kessler, 63038 Clermont-Ferrand, France Institute of Earth Sciences, University of Iceland, 101 Reykjavik, Iceland
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Abstract

A pair of samples, from host lava and an included segregation vein from the Reykjanes Peninsula, Iceland, allows the assessment of a complete fractional crystallization of an olivine tholeiite at low pressure. The final product consists of silicic glasses with bimodal composition: trondhjemitic and more rarely granitic. Compilation of data on major element compositions of Icelandic silicic rocks reveals a clear difference from those of the segregation glasses. Fractional crystallization of basalts at low pressure is therefore not the most likely mechanism for the origin of silicic magmas in Iceland. Similar conclusions have been reached in studies on O- and Th-isotope compositions. On the other hand, the trondhjemitic compositions of the glasses in the segregation vein from Reykjanes Peninsula suggest that fractional crystallization of olivine tholeiites could have played a significant role during the formation of the very early continental crust.

Keywords

Icelandfractional crystallizationtrondhjemitesegregation veininterstitial glass
Type
Original Article
Information
Geological Magazine , Volume 142 , Issue 6 , November 2005 , pp. 651 - 658
Copyright
© 2005 Cambridge University Press

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