Equation of state of hydrous Fo₉₀ ringwoodite to 45 GPa by synchrotron powder diffraction

Authors: Manghnani, M.H.; Amulele, G.; Smyth, J.R.; Holl, C.M.; Chen, G.; Prakapenka, V.; Frost, D.J.

Source: Mineralogical Magazine, Volume 69, Number 3, June 2005 , pp. 317-324(8)

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Abstract:

The equation of state of Fo₉₀ hydrous ringwoodite has been measured using X-ray powder diffraction to 45 GPa at the GSECARS beam line at the Advanced Photon Source synchrotron at Argonne National Laboratory. The sample was synthesized at 1400°C and 20 GPa in the 5000 ton multi anvil press at Bayerisches Geoinstitut in Bayreuth. The sample has the formula Mg_1.70Fe²⁺_0.19Fe³⁺_0.02H_0.13Si_1.00O₄ as determined by electron microprobe, Fourier transform infrared and Mössbauer spectroscopies, and contains ~0.79% H₂O by weight. Compression of the sample had been been measured previously to 11 GPa by single crystal X-ray diffraction. A third-order Birch-Murnaghan equation of state fit to all of the data gives V₀ = 530.49±0.07 Å³, K₀ = 174.6±;2.7 GPa and K prime

= 6.2±0.6. The effect of 1% H incorporation in the structure on the bulk modulus is large and roughly equivalent to an increase in the temperature of ~600°C at low pressure. The large value of K prime

indicates significant stiffening of the sample with pressure so that the effect of hydration decreases with pressure.

Keywords: EQUATION OF STATE; RINGWOODITE; SYNCHROTRON; BIRCH-MURNAGHAN EQUATION

Document Type: Research article

DOI: http://dx.doi.org/10.1180/0026461056930253

Publication date: 2005-06-01

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