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Composition of the upper mantle: Geophysical tests of two petrological models

Bass, Jay D. and Anderson, Don L. (1984) Composition of the upper mantle: Geophysical tests of two petrological models. Geophysical Research Letters, 11 (3). pp. 229-232. ISSN 0094-8276. https://resolver.caltech.edu/CaltechAUTHORS:20140507-083816238

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Abstract

The elastic properties of candidate mantle phases are used to test the viability of olivine-rich (pyrolitic) and CaO + Al_2O_3-rich (eclogitic) assemblages for the mantle. High temperature adiabats for each phase of interest are constructed and compared to mantle seismic properties. Both pyrolitic and eclogitic assemblages satisfy the seismic properties between ∼ 200 and 400 km. Between 400 and 670 km depth an eclogitic assemblage yields a superior match to velocities and velocity gradients. The 400 km seismic discontinuity may represent a chemical boundary between pyrolite and picritic eclogite (“piclogite”) or phase transformations in the olivine + orthopyroxene components of a piclogitic assemblage containing about 16% olivine. High velocity gradients in the transition zone may be explained by the transformation of Ca-rich cpx to majorite garnet. Seismic properties at the top of the lower mantle are consistent with pyrolite, piclogite or perovskite, implying that the 670 km discontinuity may be a chemical boundary.


Item Type:Article
Related URLs:
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http://onlinelibrary.wiley.com/doi/10.1029/GL011i003p00229/abstractPublisherArticle
http://dx.doi.org/10.1029/GL011i003p00229DOIArticle
Additional Information:© 1984 American Geophysical Union. Received December 15, 1983; accepted January 10, 1984. Paper number 4L0072. We thank D. Weidner and H. Sawamoto for preprints, and B. Hager, and T. Ahrens for helpful comments. This research was supported by NSF Grant No. EAR811-5236. Contribution No. 4000, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 92115.
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NSFEAR811-5236
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Caltech Division of Geological and Planetary Sciences4000
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Record Number:CaltechAUTHORS:20140507-083816238
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20140507-083816238
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:45548
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:07 May 2014 17:02
Last Modified:03 Oct 2019 06:32

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