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Science 4 September 1992:
Vol. 257. no. 5075, pp. 1368 - 1376
DOI: 10.1126/science.257.5075.1368
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Articles

Short-Lived Radioactivity and Magma Genesis

James Gill 1 and Michel Condomines 2

1 Earth Sciences Department, University of California, Santa Cruz, CA.
2 Centre de Recherches Volcanologiques et URA 10 CNRS, Université Blaise Pascal, 63038 Clermont-Ferrand, France

Short-lived decay products of uranium and thorium have half-lives and chemistries sensitive to the processes and time scales of magma genesis, including partial melting in the mantle and magmatic differentiation in the crust. Radioactive disequilibrium between 238U, 230Th, and 226Ra is widespread in volcanic rocks. These disequilibria and the isotopic composition of thorium depend especially on the extent and rate of melting as well as the presence and composition of vapor during melting. The duration of mantle melting may be several hundred millennia, whereas ascent times are a few decades to thousands of years. Differentiation of most magmas commonly occurs within a few millennia, but felsic ones can be tens of millennia old upon eruption.


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Constraints on the Genesis of Potassium-rich Italian Volcanic Rocks from U/Th Disequilibrium.
R. Avanzinelli, T. Elliott, S. Tommasini, and S. Conticelli (2008)
J. Petrology 49, 195-223
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Timescales of Magma Chamber Processes and Dating of Young Volcanic Rocks.
M. Condomines, M. Condomines, P.-J. Gauthier, and O. Sigmarsson (2003)
Reviews in Mineralogy and Geochemistry 52, 125-174
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References.
(1999)
Geological Society, London, Memoirs 19, 157-161
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Genesis of Evolved Ocean Island Magmas by Deep- and Shallow-Level Basement Recycling, Socorro Island, Mexico: Constraints from Th and other Isotope Signatures.
W. A. Bohrson and M. R. Reid (1998)
J. Petrology 39, 995-1008
   Abstract »    Full Text »    PDF »
Thorium-Uranium Fractionation by Garnet: Evidence for a Deep Source and Rapid Rise of Oceanic Basalts.
T. Z. LaTourrette, T. Z. LaTourrette, A. K. Kennedy, and G. J. Wasserburg (1993)
Science 261, 739-742
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