High-temperature XAS study of Fe[sub 2]SiO[sub 4] liquid: Reduced coordination of ferrous iron

Journal Article · Fri Oct 08 00:00:00 EDT 1993 · Science (Washington, D.C.); (United States)

DOI:https://doi.org/10.1126/science.262.5131.229· OSTI ID:5256776

Jackson, W E; Brown, Jr, G E; Waychunas, G A ^[1]; Leon, J.M. de; Conradson, S D ^[2]; Combes, J M ^[3]

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1. Stanford Univ., CA (United States)
2. Los Alamos National Lab., NM (United States)
3. St. Gobain Inc., Recherche (France)

X-ray absorption spectroscopy (XAS) of Fe[sup 2+] in Fe[sub 2]SiO[sub 4] liquid at 1575 kelvin and 10[sup [minus]4] gigapascal (1 bar) shows that the Fe[sup 2+]-O bond length is 1.98 [+-] 0.02 angstroms compared with [approximately]2.22 angstroms in crystalline Fe[sub 2]SiO[sub 4] (fayalite) at the melting point (1478 kelvin), which indicates a decrease in average Fe[sup 2+] coordination number from six in fayalite to four in the liquid. Anharmonicity in the liquid was accounted for using a data analysis procedure. This reduction in coordination number is similar to that observed on the melting of certain ionic salts. These results are used to develop a model of the medium-range structural environment of Fe[sup 2+] in olivine-composition melts, which helps explain some of the properties of Fe[sub 2]SiO[sub 4] liquid, including density, viscosity, and the partitioning of iron and nickel between silicate melts and crystalline olivines. Some of the implications of this model for silicate melts in the Earth's crust and mantle are discussed.

• OSTI ID: 5256776
• Journal Information: Science (Washington, D.C.); (United States), Vol. 262:5131; ISSN 0036-8075
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
58 GEOSCIENCES
IRON
COORDINATION NUMBER
IRON SILICATES
BOND LENGTHS
PHYSICAL PROPERTIES
LIQUIDS
EARTH CRUST
EARTH MANTLE
DIMENSIONS
ELEMENTS
FLUIDS
IRON COMPOUNDS
LENGTH
METALS
OXYGEN COMPOUNDS
SILICATES
SILICON COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
400201* - Chemical & Physicochemical Properties
580000 - Geosciences