Equation of state of CAS phase to pressure of the uppermost lower mantle at ambient temperature

Abstract

The CAS phase is a major constituent phase for the continental crust and basaltic compositions at the P-T conditions of the Earth's mantle, and potentially plays an important role in the geodynamic processes related to slab subduction. Its equation of state has been investigated here at ambient temperature up to about 25 GPa by using a diamond-anvil cell and synchrotron Xray radiation. Its P-V data, fitted to the third-order Birch-Murnaghan equation, yield an isothermal bulk modulus (K T ) of 185 (9) GPa and first pressure derivative ( T K ′ ) of 7.2 (12). If T K ′ is fixed at 4, the derived K T is 212 (4) GPa. Additionally, the CAS phase is strongly elastically anisotropic, with its a-axis direction much less compressible than c-axis direction: K T-a : K T-c = 2.19. anisotropic elasticity, CAS phase, equation of state, synchrotron X-ray radiation Citation: Liu X, He Q, Deng L W, et al. Equation of state of CAS phase to pressure of the uppermost lower mantle at ambient temperature.

High‐Pbehavior of anorthite composition and some phase relations of the CaO‐Al2O3‐SiO2 system to the lower mantle of the Earth, and their geophysical implications

“…Its general chemical composition was later established as CaAl 4 Si 2 O 11 by Gautron et al [1996] whereas its detailed structural characteristics were intensively investigated by Gautron et al [1997, 1999], Grey et al [1999], and Xue et al [2009]. Recently, Ono et al [2005], Liu et al [2011], and Gréaux et al [2011a] studied its equation of state up to ∼44 GPa. Its high P ‐ T phase relationships were examined in Ishibashi et al [2008], Zhai and Ito [2008], and Akaogi et al [2009].…”

Equation of State of a Natural Chromian Spinel at Ambient Temperature

“…In comparison, the approximated K T0 was only 192 GPa, being 50 GPa smaller than the experimentally-obtained value (with a large relative difference of~21%; K T0 fixed at 4). As pointed out by Fan et al [10], the 16:3:1 methanol-ethanol-water mixture pressure medium used in their experiments resulted in somewhat non-hydrostatic experimental condition at P >~10 GPa, which in turn should have led to the nominally much larger K T0 [30].…”