Lu-Hf Isotope Systematics of Garnet Pyroxenites from Beni Bousera, Morocco: Implications for Basalt Origin

American Association for the Advancement of Science (AAAS) - Tập 283 Số 5406 - Trang 1303-1306 - 1999
Janne Blichert‐Toft1, Francis Albarède1, Jacques Kornprobst2
1Ecole Normale Supérieure de Lyon and CNRS, 46 Allée d'Italie, 69364 Lyon Cedex 7, France.
2L'Unité Mixte de Recherche CNRS “Magmas et Volcans,” Observatoire de Physique du Globe de Clermont-Ferrand, 5 rue Kessler, 63038 Clermont-Ferrand, France.

Tóm tắt

Six garnet pyroxenites from Beni Bousera, Morocco, yield a mean lutetium-hafnium age of 25 ± 1 million years ago and show a wide range in hafnium isotope compositions (ɛ Hf = –9 to +42 25 million years ago), which exceeds that of known basalts (0 to +25). Therefore, primary melts of garnet pyroxenites cannot be the source of basalts. The upper mantle may be an aggregate of pyroxenites that were left by the melting of oceanic crust at subduction zones and peridotites that were contaminated by the percolation of melts from these pyroxenites. As a consequence, the concept of geochemical heterogeneities as passive tracers is inadequate. Measured lutetium-hafnium partitioning of natural minerals requires a reassessment of some experimental work relevant to mantle melting in the presence of garnet.

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Tài liệu tham khảo

10.1038/323123a0

Salters V. J. M., Hart S. R., ibid. 342, 420 (1989).

LaTourrette T. Z., Kennedy A. K., Wasserburg G. J., Science 261, 739 (1993).

Blundy J. D., Robinson J. A. C., Wood B. J., Earth Planet. Sci. Lett. 160, 493 (1998).

Wood D. A., Geology 7, 499 (1979).

10.1016/0012-821X(84)90004-9

Roy-Barman M., Allègre C. J., ibid. 129, 145 (1995).

C. C. Lundstrom Q. Williams J. B. Gill ibid. 157 151 (1998).

D. McKenzie and R. K. O'Nions J. Petrol. 32 1021 (1991).

10.1038/384231a0

Salters V. J. M., Zindler A., Earth Planet. Sci. Lett. 129, 13 (1995).

Slodkevitch V. V., Mineral. Soc. U.S.S.R. 1, 13 (1982).

Kornprobst J., Contrib. Mineral. Petrol. 23, 283 (1969).

___, Notes Serv. Geol. Maroc 251, 1 (1974).

Gjata K., Kornprobst J., Kodra A., Briot D., Pineau F., Bull. Soc. Geol. Fr. 163, 469 (1992).

Kumar N., Reisberg L., Zindler A., Geochim. Cosmochim. Acta 60, 1429 (1996).

Pearson D. G., Davies G. R., Nixon P. H., J. Petrol. 34, 125 (1993).

Loomis T. P., Am. J. Sci. 275, 1 (1975).

Duchêne S., et al., Nature 387, 586 (1997).

Ricard Y., Vigny C., J. Geophys. Res. 94, 17543 (1989).

Vergely P., Dimo A., Monié P., C. R. Acad. Sci. Paris 326, 717 (1998).

References for Hf isotope data in oceanic basalts can be obtained from J. Blichert-Toft upon request.

L. Reisberg and A. Zindler Earth Planet. Sci. Lett. 81 29 (1986/1987).

___, Jagoutz E., ibid. 96, 161 (1989).

D. G. Pearson G. R. Davies P. H. Nixon P. B. Greenwood D. P. Mattey ibid. 102 289 (1991).

10.1146/annurev.ea.14.050186.002425

M. Javoy in Orogenic Mafic and Ultramafic Association vol. 272 of Colloques Internationaux du CNRS C. J. Allègre and J. Aubouin Eds. (Editions du CNRS Paris 1980) pp. 279–287.

Lassiter J. C., Hauri E. H., Reiners P. W., Garcia M. O., Mineral. Mag. 62A, 856 (1998).

Loubet M., Allègre C. J., Nature 298, 809 (1982).

Kornprobst J., Piboule M., Roden M., Tabit A., J. Petrol. 31, 717 (1990).

10.1007/s004100050184

Hauri E. H., Earth Planet. Sci. Lett. 153, 1 (1997).

W. van Westrenen J. Blundy B. Wood Am. Mineral. in press.

Blichert-Toft J., Chauvel C., Albarède F., Contrib. Mineral. Petrol. 127, 248 (1997).

We are grateful to P. Télouk for keeping the Plasma 54 inductively coupled plasma mass spectrometer in optimum working condition. We thank two anonymous reviewers for helpful comments.

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American Association for the Advancement of Science (AAAS)

Tập 283 Số 5406

1303-1306

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