Letter abstract
Nature Geoscience 2, 548 - 552 (2009)
Published online: 20 July 2009 | doi:10.1038/ngeo579
Early martian mantle overturn inferred from isotopic composition of nakhlite meteorites
V. Debaille1,2, A. D. Brandon3, C. O'Neill4, Q.-Z. Yin5 & B. Jacobsen5
The early stages of planetary differentiation are characterized by the formation of magma oceans, which crystallize from the base up1, 2. The final, iron-rich residues of crystallization are dense and therefore tend to sink into the mantle, whereas the deeper, magnesium-rich material tends to rise up3, 4. The resultant mantle overturn would have had a profound influence on the evolution of the planets3, 4, 5, 6. Such an event probably occurred on Mars, but its initiation, timing and geochemical consequences are poorly constrained. Here we use isotopic data for nakhlite meteorites—chunks of martian crust transported to the Earth—and numerical simulations to constrain the evolution of the early martian mantle. We interpret the isotopic composition of the meteorites as evidence for an episode that occurred relatively early in Mar's history, about 100 million years after the planet's formation, during which garnet was removed from material that rose up from the deep mantle. This episode implies large-scale reorganization in the martian mantle and thereby provides compelling support for overturn. We suggest that this event probably led to substantial re-melting in the deepest mantle, which may have influenced early martian processes such as the development of crustal dichotomy.
- DSTE, Université Libre de Bruxelles, CP 160/02, 50 Avenue F. D. Roosevelt, 1050 Brussels, Belgium
- Lunar and Planetary Institute, 3600 Bay Area, Houston, Texas 77058, USA
- NASA-Johnson Space Center, Mail Code KR, Houston, Texas 77058, USA
- GEMOC ARC National Key Centre, Macquarie University, New South Wales, Australia
- Department of Geology, University of California Davis, One Shields Avenue, Davis, California 95616, USA
Correspondence to: V. Debaille1,2 e-mail: vinciane.debaille@ulb.ac.be
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