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Science 8 December 2000:
Vol. 290. no. 5498, pp. 1940 - 1944
DOI: 10.1126/science.290.5498.1940
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Reports

Geodynamic Evidence for a Chemically Depleted Continental Tectosphere

Alessandro M. Forte,* H. K. Claire Perry

The tectosphere, namely the portions of Earth's mantle lying below cratons, has a thermochemical structure that differs from average suboceanic mantle. The tectosphere is thought to be depleted in its basaltic components and to have an intrinsic buoyancy that balances the mass increase associated with its colder temperature relative to suboceanic mantle. Inversions of a large set of geodynamic data related to mantle convection, using tomography-based mantle flow models, indicate that the tectosphere is chemically depleted and relatively cold to 250 kilometers depth below Earth's surface. The approximate equilibrium between thermal and chemical buoyancy contributes to cratonic stability over geological time.

Department of Earth Sciences, University of Western Ontario, London, Ontario N6A 5B7, Canada.
*   To whom correspondence should be addressed. E-mail: aforte{at}uwo.ca

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Science. ISSN 0036-8075 (print), 1095-9203 (online)