Abstract
In situ X-ray observation has been made on Mg5SiO4 forsterite in the pressure ranges over 25-30 GPa and 1250°C using double stage multianvil system with sintered diamond anvil window and intense X-rays from synchrotm radiation. Forsterite (α-phase) transfomed into spinel (γ-phase) at 28 GPa and 800°C in the fist heating cycles of the two runs. Spinel transformed into the assemblage of perovskite and periclase in the second heating cycless at 26. 4 GPa and 1200°C and at 28. 5 GPa and 950°C. The results show that α-γ transition can proceed outside the stability field of spinel, and that the blocking temperature, above which the stable assmblage of perovskite and periclase can be formed, has a pressure dependence.
