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Science 5 June 1992:
Vol. 256. no. 5062, pp. 1427 - 1430
DOI: 10.1126/science.256.5062.1427
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Articles

Pressure-Induced Coordination Changes in Alkali-Germanate Melts: An in Situ Spectroscopic Investigation

Daniel L. Farber 1 and Quentin Williams 1

1 Earth Sciences Board and Institute of Tectonics, University of California, Santa Cruz, CA 95064

The structure of liquid Na2Ge2O5·H2O, a silicate melt analog, has been studied with Raman spectroscopy to pressures of 2.2 gigapascals. Upon compression, a peak near sim240 wavenumbers associated with octahedral GeO6 groups grows relative to a peak near sim500 wavenumbers associated with tetrahedral GeO4 groups. This change corresponds to an increase in octahedral germanium in the liquid from near 0% at ambient pressures to >50% at a pressure of 2.2 gigapascals. Silicate liquids plausibly undergo similar coordination changes at depth in the Earth. Such structural changes may generate decreases in the fusion slopes of silicates at high pressures as well as neutrally buoyant magmas within the transition zone of the Earth's mantle.

Submitted on January 30, 1992
Accepted on April 9, 1992


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Germanium coordination and the germanate anomaly.
G. S. HENDERSON and H. M. WANG (2002)
European Journal of Mineralogy 14, 733-744
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High-Temperature XAS Study of Fe2SiO4 Liquid: Reduced Coordination of Ferrous Iron.
W. E. Jackson, W. E. Jackson, J. M. de Leon, G. E. Brown Jr., G. A. Waychunas, S. D. Conradson, and J. -M. Combes (1993)
Science 262, 229-233
   Abstract »    PDF »


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