Abstract
High pressure phase transformations for all the mineral phases along the joins Mg2SiO4-Ca2-SiO4 and MgO-CaSiO3 in the system MgO-CaO-SiO2 were investigated in the pressure range between 100 and 300 kbar at about 1,000 °C, by means of the technique involving a diamond-anvil press coupled with laser heating. In addition to the four end-members, there are three stable intermediate mineral components in these two joins. Phase behaviour of all the end-member components at high pressure have been reported earlier and are reviewed here. Results of this study reveal that the three intermediate components are all unstable relative to the end-members at pressures greater than 200 kbar. Ultimately, monticellite (CaMgSiO4) decomposes into CaSiO3 (perovskite-type)+MgO; merwinite (Ca3MgSi2O8) decomposes into Ca2SiO4(K2NiF4-type)+CaSiO3 (perovskite-type)+MgO; and akermanite (Ca2MgSi2O7) decomposes into CaSiO3 (perovskite-type)+MgO. Note that the decomposition reactions of all phases studied here result in the formation of MgO. Intermediate Ca-Mg silicates transform to pure Ca-silicates plus MgO, while pure Mg2SiO4 transforms to MgSiO3+MgO.
Similar content being viewed by others
References
Ahrens, T.J., Anderson, D.L., Ringwood, A.E.: Equations of state and crystal structure of high-pressure phases of shocked silicates and oxides. Rev. Geophys. 7, 667–707 (1969)
Ito, E., Matsui, Y., Suito, K., Kawai, N.: Synthesis of γ-Mg2SiO4. Phys. Earth Planet. Inter. 8, 342–344 (1974)
Kushiro, I.: Stability field of akermanite. Carnegie Inst. Geophys. Lab. Yearbook 63, 84–86 (1964)
Kushiro, I., Yoder, H.S., Jr.: Breakdown of monticellite and akermanite at high pressure. Carnegie Inst. Geophys. Lab. Yearbook 63, 81–83 (1964)
Liu, L.: Disproportionation of Ni2SiO4 to stishovite plus bunsenite at high pressures and temperatures. Earth Planet. Sci. Lett. 24, 357–362 (1975)
Liu, L.: The post-spinel phase of forsterite. Nature 262, 770–772 (1976)
Liu, L.: High pressure Ca2SiO4, the silicate K2NiF4-isotype with crystalchemical and geophysical implications. Phys. Chem. Minerals 3, 291–299 (1978a)
Liu, L.: A new high-pressure phase of Ca2Al2SiO7 and implications for the earth's interior. Earth Planet. Sci. Lett. 40, 401–406 (1978b)
Liu, L.: The high pressure phase transformations of monticellite and implications for upper mantle mineralogy. Earth Planet. Sci. Lett. (in press, 1979a)
Liu, L.: The system enstatite-wollastonite at high pressure and temperature, with emphasis on diopside. Phys. Earth Planet. Inter. (in press, 1979b)
Liu, L., Ringwood, A.E.: Synthesis of a perovskite-type polymorph of CaSiO3. Earth Planet. Sci. Lett. 28, 209–211 (1975)
Moore, P.B., Araki, T.: Atomic arrangement of merwinite, Ca3Mg[SiO4]2, an unusual dense-packed structure of geophysical interest. Am. Mineral. 57, 1355–1374 (1972)
Ringwood, A.E., Major, A.: Synthesis of Mg2SiO4-Fe2SiO4 solid solutions. Earth Planet. Sci. Lett. 1, 241–245 (1966)
Ringwood, A.E., Major, A.: Some high-pressure transformations of geophysical significance. Earth Planet. Sci. Lett. 2, 106–110 (1967)
Ringwood, A.E., Reid, A.F.: High pressure polymorphs of olivine: the K2NiF4 type. Earth Planet. Sci. Lett. 5, 67–70 (1968)
Suito, K.: Phase transformations of pure Mg2SiO4 into a spinel structure under high pressures and temperatures. J. Phys. Earth 20, 225–243 (1972)
Trojer, F.J.: The crystal structure of a high-pressure polymorph of CaSiO3. Z. Krist. 130, 185–206 (1969)
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Liu, L.g. High pressure phase transformations in the joins Mg2SiO4-Ca2SiO4 and MgO-CaSiO3 . Contr. Mineral. and Petrol. 69, 245–247 (1979). https://doi.org/10.1007/BF00372326
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00372326