A new high-pressure phase transition in clinoferrosilite: In situ single-crystal X-ray diffraction study

作者：Pakhomova Anna^*; Ismailova Leyla; Bykova Elena; Bykov Maxim; Ballaran Tiziana Boffa; Dubrovinsky Leonid

来源：American Mineralogist, 2017, 102(3): 666-673.

DOI：10.2138/am-2017-5853

• Pyroxene
• single-crystal X-ray diffraction
• high-pressure
• high-temperature
• phase transitions

Synchrotron-based high-pressure single-crystal X-ray diffraction experiments were conducted on synthetic pure clinoferrosilite, Fe2Si2O6, at room temperature to a maximum pressure of 45 GPa. In addition to the previously described P2(1)/c. C2/c phase transition between 1.48 and 1.75 GPa (HughJones et al. 1994), we observe further transition between 30 and 36 GPa into the high-pressure P2(1)/c phase (HP-P2(1)/c). The C2/c -> HP-P2(1)/c transition is induced by rearrangement of half of the layers of corner-sharing SiO4 tetrahedra into layers of edge-sharing SiO6 octahedra. The new configuration of VISi layers suggests a possibility of a progressive transformation of the pyroxene into an ilmenitetype structure. The persistence of metastable pyroxene up to pressures higher than expected and its feasible direct transformation to ilmenite are of special interest for understanding the dynamics of cold-subducting slabs. We report on structural and compressibility features of both high-pressure phases as well as address thermal stability of HP-P2(1)/c.

• 出版日期2017-3