High-pressure phase transformations in the MgFe2O4 and Fe2O3–MgSiO3 systems |
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| Authors: | D Andrault N Bolfan-Casanova |
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| Institution: | Laboratoire des Géomatériaux, IPGP, 4 place Jussieu, 75252 Paris, France e-mail: andrault@ipgp.jussieu.fr Tel.: +33 1 44 27 48 89; Fax: +33 1 44 27 24 87, FR
Bayerisches Geoinstitut, Universit?t Bayreuth, 95440 Bayreuth, Germany Now at Laboratoire des Géomatériaux, IPGP, DE
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| Abstract: | The crystal structure of MgFe2O4 was investigated by in situ X-ray diffraction at high pressure, using YAG laser annealing in a diamond anvil cell. Magnesioferrite
undergoes a phase transformation at about 25 GPa, which leads to a CaMn2O4-type polymorph about 8% denser, as determined using Rietveld analysis. The consequences of the occurrence of this dense MgFe2O4 form on the high-pressure phase transformations in the (MgSi)0.75(FeIII)0.5O3 system were investigated. After laser annealing at about 20 GPa, we observe decomposition to two phases: stishovite and a
spinel-derived structure with orthorhombic symmetry and probably intermediate composition between MgFe2O4 and Mg2SiO4. At pressures above 35 GPa, we observe recombination of these products to a single phase with Pbnm perovskite structure.
We thus conclude for the formation of Mg3Fe2Si3O12 perovskite.
Received: 27 March 2000 / Accepted: 1 October 2000 |
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| Keywords: | Magnesioferrite Spinel Perovskite Phase transformation X-ray Diffraction |
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