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Book Chapter

The significance of seismic wavespeed minima and thermal maxima in the mantle and the role of dynamic melting

By
Charles G. Sammis
Charles G. Sammis
Department of Earth Sciences, University of Southern California, Los Angeles, California 90089-0740, USA
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Don L. Anderson
Don L. Anderson
Seismological Laboratory, California Institute of Technology, MS 252-21, Pasadena, California 91125, USA
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Published:
October 01, 2015

It is widely assumed that the boundary layer above the core is the source of intraplate volcanoes such as Hawaii, Samoa, and Yellowstone, and that the sub-plate boundary layer at the top of the mantle is thin and entirely subsolidus. In fact, this upper layer is thicker and has higher expansivity, buoyancy, and insulating power than the lower one, and may have higher potential temperatures. The observed seismic structure of the low-velocity zone (LVZ) including attenuation, anisotropy, sharp boundaries, and a reduction of both compressional and shear moduli can be taken as strong evidence for the ubiquitous presence of melt in the upper mantle. If the LVZ contains as little as 1%–2% melt, then it is the most plausible and accessible source for midplate magmas; deeply rooted active upwellings are unnecessary. The upper boundary layer is also the most plausible source of ancient isotopic signatures of these magmas and their inclusions.

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Contents

GSA Special Papers

The Interdisciplinary Earth: A Volume in Honor of Don L. Anderson

Gillian R. Foulger
Gillian R. Foulger
Department of Earth Sciences, Durham University, Durham DH1 3LE, UK
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Michele Lustrino
Michele Lustrino
Dipartimento di Scienze della Terra, Universita` degli Studi di Roma La Sapienza, P.le A. Moro, 5, 00185 Roma, Italy
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Scott D. King
Scott D. King
Department of Geosciences, Virginia Tech, Blacksburg, Virginia 24061, USA
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Geological Society of America
Volume
514
ISBN print:
9780813725147
Publication date:
October 01, 2015

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