MR13B-2698
Synthesis and equation of state of high pressure phase of chromium-bearing spinel
Monday, 14 December 2015
Poster Hall (Moscone South)
Sean R Shieh1, Tauhid Khan1, Clemens Prescher2, Vitali Prakapenka3 and Zhongying MI4, (1)University of Western Ontario, Department of Earth Sciences, London, ON, Canada, (2)University of Chicago, Center for Advanced Radiation Sources, Chicago, IL, United States, (3)University of Chicago, Argonne, IL, United States, (4)Center for High Pressure Science and Technology Advanced Research, Shanghai, China
Abstract:
Chromium-bearing spinel (Mg,Fe)Cr2O4 can be found in the Earth’s crust, upper mantle, and even in meteorites. Mantle derived chromium-bearing spinel suggests that its high pressure phase may be existing at deep mantle but however its high pressure elastic property is not well understood yet. In situ synchrotron X-ray diffraction studies of magnesiochromite and chromite using the laser-heated diamond anvil cell were performed at GSECARS, Advanced Photon Source, to explore their high pressure phases and elastic property. Our results on magnesiochromite showed dissociation of MgCr2O4 to Cr2O3+MgO at ~15 GPa and to modified Ludwigite (mLd)-type Mg2Cr2O5+Cr2O3 below and above ~1500 K, respectively. At above 20 GPa, only a single phase CaTi2O4-type structure of MgCr2O4 was observed at 1400-2000 K. Pressure-volume data of CaTi2O4 type structure of MgCr2O4 fitted to Birch-Murnaghan equation of state yield zero-pressure volume (V0) = 264.4(8) Å3, bulk modulus (K0) = 185.4(4) GPa, and pressure derivative (K0’) = 4; and mLd-type Mg2Cr2O5 yields: V0 = 338.9(8) Å3, K0 = 186.5(6) GPa, K0’ = 4. For CaTi2O4 type structure of natural chromite, our fitted P-V data show V0 = 261(1) Å3, K0 = 175.4(2) GPa, and K0’ = 4.
