The Postspinel Phases in the Mg2SiO4-Fe2SiO4 System

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Science  10 Jan 1975:
Vol. 187, Issue 4171, pp. 66-68
DOI: 10.1126/science.187.4171.66


Samples of olivine (Fo0Fa100, Fo60Fa40, Fo80Fa20, and Fo100Fa0) and of spinel (Fo50Fa50, Fo2Fa100, where Fo is forsterite and Fa is fayalite) were subjected to pressures up to 250 kilobars in a diamond anvil press and were heated in situ up to ~ 1700°C by an infrared beam from a continuous-wave YAG (yttrium-aluminum-garnet) laser. The brightness temperature was determined from the intensity of incandescence of the sample by means of an optical pyrometer. X-ray diffraction patterns of the samples, obtained after quenching and unloading, show conclusively that these compositions disproportionate to (Mg, Fe)O and SiOs (stishovite) under these conditions.