Hf isotope evidence for a hidden mantle reservoir
- 1Centre for Research in Isotopic Geochemistry and Geochronology (GÉOTOP), Université du Québec à Montréal, succursale Centre-ville, CP 8888, Montréal, Québec H3C 3P8, Canada
Abstract
High-precision Hf isotopic analyses and U-Pb ages of carbonatites and kimberlites from Greenland and eastern North America, including Earth's oldest known carbonatite (3 Ga), indicate derivation from an enriched mantle source. This previously unidentified mantle reservoir—marked by an unradiogenic Hf isotopic composition and preserved in the deep mantle for at least 3 b.y.—may account for the mass imbalance in Earth's Hf-Nd budget. The Hf isotopic data presented here support a common mantle source region and genetic link between carbonatite and some oceanic- island basalt volcanoes.
Footnotes
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↵*Present address: Geologisk Museum, Øster Voldgade 5-7, 1350 Copenhagen K., Denmark
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↵GSA Data Repository item 2002089, U-Pb, Lu-Hf, and Sm-Nd data tables, is available on request from Documents Secretary, GSA, P.O. Box 9140, Boulder, CO 80301-9140, USA, editinggeosociety.org, or at www. geosociety. org/ pubs/ ft2002. htm.
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- Accepted May 2, 2002.
- Received January 31, 2002.
- Revision received April 30, 2002.
- Geological Society of America
