Melting dynamics beneath the Tonga-Kermadec island arc inferred from 231Pa-235U systematics

Science

Volumn 286, Issue 5449, 1999, Pages 2491-2493

  Bourdon, Bernard ^a   Turner, Simon ^b   Allègre, Claude ^a  

^a INSTITUT DE PHYSIQUE DU GLOBE DE PARIS   (France)

^b OPEN UNIVERSITY   (United Kingdom)

Author keywords

[No Author keywords available]

Indexed keywords

ISOTOPE; PROTACTINIUM; URANIUM;

ISLAND ARC; MAGMATISM; PARTIAL MELTING;

ARTICLE; CHEMICAL ANALYSIS; GEOGRAPHIC DISTRIBUTION; GEOLOGY; MELTING POINT; NATURAL SCIENCE; PRIORITY JOURNAL; TONGA;

PACIFIC OCEAN;

EID: 0033601379     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.286.5449.2491     Document Type: Article

References (29)

1. A recent summary is given by C. J. Hawkesworth, S. P. Turner, F. McDermott, D. W. Peate, and P. van Calsteren [Science 276, 551 (1997)].
2. For example, C. C. Lundstrom, J. Gill, Q. Williams, B. B. Hanan, Earth Planet. Sci. Lett. 157, 167 (1998); B. Bourdon, J.-L. Joron, C. Claude-lvanaj, C. J. Allègre, Earth Planet. Sci. Lett. 164, 119 (1998).
3. For example, C. C. Lundstrom, J. Gill, Q. Williams, B. B. Hanan, Earth Planet. Sci. Lett. 157, 167 (1998); B. Bourdon, J.-L. Joron, C. Claude-lvanaj, C. J. Allègre, Earth Planet. Sci. Lett. 164, 119 (1998).
4. D. A. Pickett and M. T. Murrell, Earth Planet. Sci. Lett. 148, 259 (1997).
5. T. Plank and C. H. Langmuir, Earth Planet. Sci. Lett. 90, 349 (1988); J. A. Pearce and I. J. Parkinson, Geol. Soc. Spec. Publ. 76, 373 (1993).
6. T. Plank and C. H. Langmuir, Earth Planet. Sci. Lett. 90, 349 (1988); J. A. Pearce and I. J. Parkinson, Geol. Soc. Spec. Publ. 76, 373 (1993).
7. J. H. Davies and D. J. Stevenson, J. Geophys. Res. 97, 2037 (1992).
8. D. M. Miller, S. L. Goldstein, C. H. Langmuir, Nature 368, 514 (1994); E. Stolper and S. Newman, Earth Planet. Sci. Lett. 121, 293 (1994).
9. D. M. Miller, S. L. Goldstein, C. H. Langmuir, Nature 368, 514 (1994); E. Stolper and S. Newman, Earth Planet. Sci. Lett. 121, 293 (1994).
10. M. Bevis et al., Nature 374, 249 (1995).
11. Indices of depletion, such as low Al/Ti and Ca/Ti ratios and Na and Fe contents, increase northward from Kermadec to Tonga concomitant with increases in the complexity and rate of back-arc spreading (9, 10).
12. A. Ewart and C. J. Hawkesworth, J. Petrol. 28, 495 (1987); A. Ewart, K. D. Collerson, M. Regelous, J. I. Wendt, Y. Niu, J. Petrol. 39, 331 (1998).
13. A. Ewart and C. J. Hawkesworth, J. Petrol. 28, 495 (1987); A. Ewart, K. D. Collerson, M. Regelous, J. I. Wendt, Y. Niu, J. Petrol. 39, 331 (1998).
14. S. Turner and C. Hawkesworth, Nature 389, 568 (1997); S. Turner et al., Geochim. Cosmochim. Acta 61, 4855 (1997).
15. S. Turner and C. Hawkesworth, Nature 389, 568 (1997); S. Turner et al., Geochim. Cosmochim. Acta 61, 4855 (1997).
16. M. Regelous, K. D. Collerson, A. Ewart, J. I. Wendt, Earth Planet. Sci. Lett. 150, 291 (1997).
17. Protactinium-231 concentrations were measured following the technique described by B. Bourdon, J.-L. Joron, and C. J. Allègre [Chem. Geol. 157, 147 (1999)].
18. C. J. Allègre and M. Condomines, Nature 299, 21 (1982).
19. J. M. Brenan, H. F. Shaw, F. J. Ryerson, D. L. Phinney, Geochim. Cosmochim. Acta 59, 3331 (1995); H. Keppler Nature 380, 237 (1996). Protactinium has been shown to be a very insoluble element in aqueous solutions [R. Guillaumont, G. Bouissières, R. Muxart, Actinides Rev. 1, 135 (1968)].
20. J. M. Brenan, H. F. Shaw, F. J. Ryerson, D. L. Phinney, Geochim. Cosmochim. Acta 59, 3331 (1995); H. Keppler Nature 380, 237 (1996). Protactinium has been shown to be a very insoluble element in aqueous solutions [R. Guillaumont, G. Bouissières, R. Muxart, Actinides Rev. 1, 135 (1968)].
21. J. M. Brenan, H. F. Shaw, F. J. Ryerson, D. L. Phinney, Geochim. Cosmochim. Acta 59, 3331 (1995); H. Keppler Nature 380, 237 (1996). Protactinium has been shown to be a very insoluble element in aqueous solutions [R. Guillaumont, G. Bouissières, R. Muxart, Actinides Rev. 1, 135 (1968)].
22. T. Elliott, T. Plank, A. Zindler, W. White, B. Bourdon, J. Geophys. Res. 102, 14991 (1997).
23. The melting process has to have reproducibly fractionated Pa/U by the same amount to preserve the isochron relationship in Fig. 2. If we assume 50,000 years elapsed since U addition, based on U-Th data (9), the Pa enrichment relative to U due to melting cannot have been greater than -10%.
24. -5 (B. Wood and J. Blundy, personal communication).
25. -3.
26. In fertile peridotite, clinopyroxene remains a residual phase until ∼22% melting [A. L. Jaques and D. H. Green, Contrib. Mineral. Petrol. 73, 287 (1980)]. However, peridotites depleted by ∼7% melt extraction, such as the Tinaquillo spinel iherzolite, contain less clinopyroxene; consequently, this ceases to be a residual phase after only ∼8% partial melting [J. A. C. Robinson and B. J. Wood. Earth Planet. Sci. Lett. 164, 277 (1998); L. E. Wasylenski, M. B. Baker, M. M. Hirschmann, E. M. Stolper, Eos (Fall Suppl.) 77, F847 (1996)].
27. In fertile peridotite, clinopyroxene remains a residual phase until ∼22% melting [A. L. Jaques and D. H. Green, Contrib. Mineral. Petrol. 73, 287 (1980)]. However, peridotites depleted by ∼7% melt extraction, such as the Tinaquillo spinel iherzolite, contain less clinopyroxene; consequently, this ceases to be a residual phase after only ∼8% partial melting [J. A. C. Robinson and B. J. Wood. Earth Planet. Sci. Lett. 164, 277 (1998); L. E. Wasylenski, M. B. Baker, M. M. Hirschmann, E. M. Stolper, Eos (Fall Suppl.) 77, F847 (1996)].
28. In fertile peridotite, clinopyroxene remains a residual phase until ∼22% melting [A. L. Jaques and D. H. Green, Contrib. Mineral. Petrol. 73, 287 (1980)]. However, peridotites depleted by ∼7% melt extraction, such as the Tinaquillo spinel iherzolite, contain less clinopyroxene; consequently, this ceases to be a residual phase after only ∼8% partial melting [J. A. C. Robinson and B. J. Wood. Earth Planet. Sci. Lett. 164, 277 (1998); L. E. Wasylenski, M. B. Baker, M. M. Hirschmann, E. M. Stolper, Eos (Fall Suppl.) 77, F847 (1996)].
29. We are grateful to A. Ewart, T. Worthington, S. Acland, J. Pearce, A. Reay, I. Smith, and J. Gamble for their generosity in providing samples and to J. L. Joron for his help. We also thank C. Hawkesworth for helpful discussions and careful reading of the manuscript. Careful reviews by R. Arculus and anonymous reviewers led to significant improvements. B.B. was funded by CNRS and S.T. by a Royal Society Research Fellowship. This is IPGP contribution no. 1647.