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Science 18 May 2001:
Vol. 292. no. 5520, pp. 1363 - 1366
DOI: 10.1126/science.1059904
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Reports

Ultrafast Source-to-Surface Movement of Melt at Island Arcs from 226Ra-230Th Systematics

Simon Turner,12* Peter Evans,13 Chris Hawkesworth12

Island arc lavas have radium-226 excesses that extend to higher values than those observed in mid-ocean ridge or ocean island basalts. The initial ratio of radium-226 to thorium-230 is largest in the most primitive lavas, which also have the highest barium/thorium ratios, and decreases with increasing magmatic differentiation. Therefore, the radium-226 excesses appear to have been introduced into the base of the mantle melting column by fluids released from the subducting plate. Preservation of this signal requires transport to the surface arguably in only a few hundreds of years and directly constrains the average melt velocity to the order of 1000 meters per year. Thus, melt segregation and channel formation can occur rapidly in the mantle.

1 Department of Earth Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK.
2 Department of Earth Sciences, Wills Memorial Building, University of Bristol, Bristol BS8 1RJ, UK.
3 Laboratories of the Government Geochemist, Queens Road, Teddington, Middlesex PW11 0LY, UK.
*   To whom correspondence should be addressed. E-mail: simon.turner{at}bristol.ac.uk

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Generation of Rear-arc Magmas Induced by Influx of Slab-derived Supercritical Liquids: Implications from Alkali Basalt Lavas from Rishiri Volcano, Kurile Arc.
T. Kuritani, T. Yokoyama, and E. Nakamura (2008)
J. Petrology 49, 1319-1342
   Abstract »    Full Text »    PDF »
Some first-order observations on magma transfer from mantle wedge to upper crust at volcanic arcs.
G. F. Zellmer (2008)
Geological Society, London, Special Publications 304, 15-31
   Abstract »    Full Text »    PDF »
Uranium-series isotope and thermal constraints on the rate and depth of silicic magma genesis.
A. Dosseto, S. P. Turner, M. Sandiford, and J. Davidson (2008)
Geological Society, London, Special Publications 304, 169-181
   Abstract »    Full Text »    PDF »
226Ra/230Th excess generated in the lower crust: Implications for magma transport and storage time scales.
J. Dufek and K. M. Cooper (2005)
Geology 33, 833-836
   Abstract »    Full Text »    PDF »
Time scale of magma differentiation in arcs from protactinium-radium isotopic data.
Y. Asmerom, S. A. DuFrane, S. B. Mukasa, H. Cheng, and R. L. Edwards (2005)
Geology 33, 633-636
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Fluid-metasedimentary rock interactions in subduction-zone melange: Implications for the chemical composition of arc magmas.
(2004)
Geology 32, 1041-1044
Chemical versus Temporal Controls on the Evolution of Tholeiitic and Calc-alkaline Magmas at Two Volcanoes in the Alaska-Aleutian Arc.
R. GEORGE, S. TURNER, C. HAWKESWORTH, C. R. BACON, C. NYE, P. STELLING, and S. DREHER (2004)
J. Petrology 45, 203-219
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Time-scales of Differentiation from Mafic Parents to Rhyolite in North American Continental Arcs.
M. K. REAGAN, K. W. W. SIMS, J. ERICH, R. B. THOMAS, H. CHENG, R. L. EDWARDS, G. LAYNE, and L. BALL (2003)
J. Petrology 44, 1703-1726
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Rates and Processes of Potassic Magma Evolution beneath Sangeang Api Volcano, East Sunda Arc, Indonesia.
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J. Petrology 44, 491-515
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Compositional variations within scoria cones.
(2003)
Geology 31, 143-146
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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Uranium-series Disequilibria in Mid-ocean Ridge Basalts: Observations and Models of Basalt Genesis.
C. C. Lundstrom and C. C. Lundstrom (2003)
Reviews in Mineralogy and Geochemistry 52, 175-214
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Insights into Magma Genesis at Convergent Margins from U-series Isotopes.
S. P. Turner, S. Turner, B. Bourdon, and J. Gill (2003)
Reviews in Mineralogy and Geochemistry 52, 255-315
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Some geochemical constraints on hot fingers in the mantle wedge: evidence from NE Japan.
Y. Tamura (2003)
Geological Society, London, Special Publications 219, 221-237
   Abstract »    PDF »
Multiple subduction components in the mantle wedge: Evidence from eruptive centers in the Central Southern volcanic zone, Chile.
(2002)
Geology 30, 199-202


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Science. ISSN 0036-8075 (print), 1095-9203 (online)