Compressibility and thermal expansion of natural clinopyroxene Di0.66Hd0.13Jd0.12Ts0.05

Abstract

Abstract A natural clinopyroxene (cpx) has been experimentally studied by in-situ X-ray powder diffraction combined with an externally heated diamond anvil cell (DAC) technique in the temperature range 300–673 K and at pressures up to 15 GPa. The specimen has a composition of Di0.66Hd0.13Jd0.12Ts0.05 on the basis of four end-members, diopside (CaMgSi2O6), hedenbergite (CaFeSi2O6), jadeite (NaAlSi2O6), and Mg-Tschermak (MgAl(AlSi)O6). By combining the current data with literature results, an empirical relationship, V0 (A3) = 392.5(6.2) + 46.7(6.5) × Di + 57.6(6.3) × Hd + 9.9(6.2) × Jd has been obtained to describe the relationship between the unit-cell volume and the composition of Di-Jd-Hd solid solution. The isothermal bulk modulus KT0 = 112(3) GPa and its pressure derivative K′T0 = 5.0(7) are obtained by fitting pressure-volume data with a 3rd-order Birch-Murnaghan equation of state (B-M EoS). The volume thermal expansion coefficients are determined to be α0 = 2.97(8) × 10−5/K and 2.82(2) × 10−5/K at ∼6.9(2) GPa and 8.5(2) GPa, respectively, from which ∂α/∂P = −9.3 × 10−7/K GPa−1 and ∂KT/∂T = −0.012 GPa/K are resulted for the current Di0.66Hd0.13Jd0.12Ts0.05.