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Seismic and Mineral Physics Constraints on the D" Layer

Jackson, Jennifer M. and Thomas, Christine (2021) Seismic and Mineral Physics Constraints on the D" Layer. In: Mantle Convection and Surface Expressions. American Geophysical Union , Hoboken, NJ, pp. 193-228. ISBN 9781119528616.

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We present a synthesis of results from seismic and mineral physics studies of the D" layer to improve constraints on Earth's lowermost mantle. We focus on structures of two length scales, the seismic reflector at the top of this region and the structures of smaller scale known as ultralow velocity zones (ULVZs). A review of seismic observations for the D" layer and their interpretation is followed by a case study, where we combine new data with published results for the D" region beneath the Bering Sea and Alaska. Our evaluation of plausible interpretations includes features related to subducted slab debris that trade-off with petrology (mineral phase assemblage) and post-perovskite crystal chemistry. For the smaller-scale structures that exhibit lower than average seismic wavespeeds, the ULVZs, we consider hypotheses involving either iron-rich (Mg,Fe)O magnesiowüstite or iron-rich (Mg,Fe)SiO₃ post-perovskite. We use mineral physics data and previously published seismic reduction ratios of S- and P-wavespeeds with their respective uncertainties for a best-fit optimization approach with parameter correlations. Seismic wave reduction ratios ranging from 2 to 3 are well explained by phase assemblages containing elastically anisotropic iron-rich (Mg,Fe)O. Observations outside this range require different explanations than those considered here, thus suggesting diverse origins for ULVZs.

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Jackson, Jennifer M.0000-0002-8256-6336
Additional Information:© 2021 American Geophysical Union. Published Online: 11 June 2021. We are sincerely thankful to our dear friend and colleague, Don Helmberger (Caltech), for all the thoughtful discussions about D" and Earth’s interior. We would also like to thank Wolfgang Sturhahn (Caltech) for his help with developing the mineral mixing model and Vasilije Dobrosavljevic (Caltech) for related discussions, and Angelo Pisconti (U. Münster) for comments on the chapter. We thank Jeroen Ritsema (U. MI), two anonymous reviewers, and the editor Hauke Marquardt for their careful reviews. J.M.J. thanks the National Science Foundation’s Collaborative Study of Earth’s Deep Interior (EAR-1161046 and 2009935), the Internationalization Office of WWU, Münster, and Caltech for support.
Group:Seismological Laboratory
Funding AgencyGrant Number
Westfälische Wilhelms-UniversitätUNSPECIFIED
Subject Keywords:D" Layer; mineral phase assemblages; mineral physics constraints; post-perovskite crystal chemistry; seismic constraints; ultralow velocity zones
Record Number:CaltechAUTHORS:20210622-164157641
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Official Citation:Jackson, J.M. and Thomas, C. (2021). Seismic and Mineral Physics Constraints on the D" Layer. In Mantle Convection and Surface Expressions (eds H. Marquardt, M. Ballmer, S. Cottaar and J. Konter).
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:109527
Deposited By: Tony Diaz
Deposited On:23 Jun 2021 19:27
Last Modified:24 Jun 2021 20:47

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