Cryptic striations in the upper mantle revealed by hafnium isotopes in southeast Indian ridge basalts

The Earth's mantle is isotopically heterogeneous on length scales ranging from centimetres to more than 104 kilometres. This heterogeneity originates from partial melt extraction and plate tectonic recycling, whereas stirring during mantle convection tends to reduce it. Here we show that mid-oc...

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Bibliographic Details
Published inNature Vol. 440; no. 7081; pp. 199 - 202
Main Authors Graham, D. W, Albarède, F, Russo, C. J, Blichert-Toft, J, Rubin, K. H
Format Journal Article
LanguageEnglish
Published London Nature Publishing Group 09.03.2006
Subjects
Basalt
Convection
Earth mantle
Earth Sciences
Geochemistry
Geology
Hafnium
Heterogeneity
Isotopes
Marine
Plate tectonics
Recycling
Sciences of the Universe
Upper mantle
India
ISW, Indian Ocean, Southeast Indian Ridge
ISW, Indian Ocean
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Summary:The Earth's mantle is isotopically heterogeneous on length scales ranging from centimetres to more than 104 kilometres. This heterogeneity originates from partial melt extraction and plate tectonic recycling, whereas stirring during mantle convection tends to reduce it. Here we show that mid-ocean ridge basalts from 2,000 km along the southeast Indian ridge (SEIR) display a bimodal hafnium isotopic distribution. This bimodality reveals the presence of ancient compositional striations (streaks) in the Indian Ocean upper mantle. The number density of the streaks is described by a Poisson distribution, with an average thickness of ∼40 km. Such a distribution is anticipated for a well-stirred upper mantle, in which heterogeneity is continually introduced by plate tectonic recycling, and redistributed by viscous stretching and convective refolding.
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ISSN:0028-0836
1476-4687
1476-4679
DOI:10.1038/nature04582