Short magma chamber residence time at an Icelandic volcano inferred from U-series disequilibria

THE questions of how quickly magmas can differentiate and how long they reside in magma chambers are fundamental to our understanding of magma evolution and the behaviour of volcanoes. Timescales of a few years to a few hundred years have been inferred from physical modelling of crystallization 1,2...

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Bibliographic Details
Published in:Nature (London) 1996-08, Vol.382 (6590), p.440-442
Main Author: Sigmarsson, Olgeir
Format: Article
Language:English
Subjects:
Basalt
Crystalline rocks
Crystallography
Earth sciences
Earth, ocean, space
Evolution
Exact sciences and technology
Fractionation
Geochronology
Humanities and Social Sciences
Igneous and metamorphic rocks petrology, volcanic processes, magmas
Isotope geochemistry. Geochronology
Lava
letter
Magma
multidisciplinary
Radium isotopes
Radium radioisotopes
Science
Science (multidisciplinary)
Volcanoes
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Summary:THE questions of how quickly magmas can differentiate and how long they reside in magma chambers are fundamental to our understanding of magma evolution and the behaviour of volcanoes. Timescales of a few years to a few hundred years have been inferred from physical modelling of crystallization 1,2 , and from variations in crystal sizes and magma compositions 3–5 . Shortlived disequilibria between daughter nuclides of the 238 U decay series yield information about the processes and timescales of magma differentiation 4,6–14 . Here I report excesses of 226 Ra over 230 Th and 210 Pb that decrease with differentiation, in lavas from the Vestmannaeyjar volcanic system (Iceland). The decreasing disequilibria can be explained by crystal fractionation of alkali basalt to form hawaiite and mugearite and a 10-year magma chamber residence time. Such rapid differentiation and so short a residence time in a deep reservoir probably result from the injection of a small volume of alkali basalt into a relatively cold crust.
ISSN:0028-0836
1476-4687
DOI:10.1038/382440a0