Nd and Sr isotopes from diamondiferous eclogites, Udachnaya Kimberlite Pipe, Yakutia, Siberia: Evidence of differentiation in the early Earth?

Nd and Sr isotopic data from diamond-bearing eclogites found in the Udachnaya kimberlite, Yakutia, Siberia, are interpreted as indicating an early ([ges] 4 Ga) differentiation event, whereby the mantle split into complementary depleted and enriched reservoirs. Reconstructed whole-rock 87Sr/86Sr rati...

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Bibliographic Details
Published in:Earth and Planetary Science Letters
Main Authors: Snyder, Gregory A., Jerde, Eric A., Taylor, Lawrence A., Halliday, Alexander N., Sobolev, Vladimir N., Sobolev, Nikolai V.
Other Authors: Department of Geological Sciences, University of Michigan, Ann Arbor, MI 48109, USA, Department of Geological Sciences, University of Tennessee, Knoxville, TN 37996, USA, Institute of Mineralogy and Petrography, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
Format: Article in Journal/Newspaper
Language:English
Published: Elsevier 1993
Subjects:
Online Access:https://hdl.handle.net/2027.42/30700
http://www.sciencedirect.com/science/article/B6V61-47251VV-1W/2/c26fa91062d2a8af0e093f61b20adc9e
https://doi.org/10.1016/0012-821X(93)90161-2
Description
Summary:Nd and Sr isotopic data from diamond-bearing eclogites found in the Udachnaya kimberlite, Yakutia, Siberia, are interpreted as indicating an early ([ges] 4 Ga) differentiation event, whereby the mantle split into complementary depleted and enriched reservoirs. Reconstructed whole-rock 87Sr/86Sr ratios (present-day) range from 0.70151 to 0.70315 and are consistent with a mantle origin for these rocks. The Nd isotopic evolution lines of four samples (U-5, U-37, U-41 and U-79) converge at 2.2-2.7 Ga. Sample U-5 is unique in exhibiting the most enriched signature of any of the samples yet analyzed (present-day [epsilon]Nd of -20), and this sample points unequivocally to an old, enriched component. A complementary depleted mantle component is suggested by two of the eclogite samples, U-86 and U-25, which yield [epsilon]Nd values (at 2.2 Ga) of + 13 and + 7, respectively. The two mantle reservoirs possibly formed prior to 4 Ga and evolved separately until 2.2-2.7 Ga. At that time, the reservoirs were melted forming eclogites both as residues (from the enriched reservoir) and as partial melts of peridotite (from the depleted reservoir), resulting in demonstrably different histories for eclogites from the same locality. Peer Reviewed http://deepblue.lib.umich.edu/bitstream/2027.42/30700/1/0000345.pdf