The thermal equation of state of (Fe0.86Mg0.07Mn0.07)3Al2Si3O12 almandine

In situ X-ray diffraction measurements on almandine. (Fe0.86Mg0.07Mn0.07)(3)Al2Si3O12 were performed, using a heating diamond-anvil cell instrument with synchrotron radiation at Beljing Synchrotron Radiation Facility up to 27.7 Gpa and 533 K. The pressure-volume-temperature data were fitted to a third-order Birch-Munlaghan equation of state. The isothermal bulk Modulus of K-0 = 177 +/- 2 GPa, a temperature derivative of the bulk modulus of (partial derivative K partial derivative T)(p)= -0.032 +/- 0.016 GpaK(-1) and a thermal expansion coefficient (alpha(0)) of (3.1 +/- 0.7)x 10(-5) K-1 were obtained. This is the first time that the temperature derivative of the bulk modulus of almandine has been determined at high pressure and high temperature. Combining these results With previous results, the compositional dependence of the bulk modulus, thermal expansion, and temperature derivative of the bulk modulus are discussed.