Zoisite is a typical accessory mineral of eclogite; understanding its compressional behavior is important for the knowledge of the properties and processes within subduction zones. In this study, the compressional behavior of a natural eclogitic zoisite Ca_1.99(Al_2.87Fe_0.11)Si_3.00O₁₂OH was investigated at ambient temperature and high pressure to 34 GPa, using a diamond anvil cell (DAC) combined with synchrotron-based single-crystal X-ray diffraction (XRD) method. Our results indicate that zoisite is stable over the experimental pressure range. The pressure–volume (P–V) data were fitted to a third-order Birch–Murnaghan equation of state (BM3 EoS), and the equation of state coefficients including zero-pressure unit-cell volume (V₀), isothermal bulk modulus (K_T0), and its pressure derivative (K′T0KT0′) were obtained as: V₀ = 904.77(8) ų, K_T0 = 118(1) GPa, and K′T0KT0′ = 6.3(2), respectively. The axial compressibilities (β) for a-, b-, and c-axes were also obtained using a parameterized form of the BM3 EoS, and the results show β_a0 < β_b0 < β_c0 with β_a0:β_b0:β_c0 = 1:1.28:1.50. In addition, the bulk modulus of this study is very consistent with previously studied zoisite with similar Fe content. However, the axial compressibility is significantly different with the previous study and the compression of zoisite in this study is more isotropic, which may result from the difference in the pressure-transmitting medium.

Zoisite is a typical accessory mineral of eclogite; understanding its compressional behavior is important for the knowledge of the properties and processes within subduction zones. In this study, the compressional behavior of a natural eclogitic zoisite Ca_1.99(Al_2.87Fe_0.11)Si_3.00O₁₂OH was investigated at ambient temperature and high pressure to 34 GPa, using a diamond anvil cell (DAC) combined with synchrotron-based single-crystal X-ray diffraction (XRD) method. Our results indicate that zoisite is stable over the experimental pressure range. The pressure–volume (P–V) data were fitted to a third-order Birch–Murnaghan equation of state (BM3 EoS), and the equation of state coefficients including zero-pressure unit-cell volume (V₀), isothermal bulk modulus (K_T0), and its pressure derivative (K′T0KT0′) were obtained as: V₀ = 904.77(8) ų, K_T0 = 118(1) GPa, and K′T0KT0′ = 6.3(2), respectively. The axial compressibilities (β) for a-, b-, and c-axes were also obtained using a parameterized form of the BM3 EoS, and the results show β_a0 < β_b0 < β_c0 with β_a0:β_b0:β_c0 = 1:1.28:1.50. In addition, the bulk modulus of this study is very consistent with previously studied zoisite with similar Fe content. However, the axial compressibility is significantly different with the previous study and the compression of zoisite in this study is more isotropic, which may result from the difference in the pressure-transmitting medium.