Epidote is a typical hydrous mineral in subduction zones. Here, we report a synchrotron-based single-crystal X-ray diffraction (XRD) study of natural epidote [Ca_1.97Al_2.15Fe_0.84(SiO₄)(Si₂O₇)O(OH)] under simultaneously high pressure-temperature (high P-T) conditions to ∼17.7 GPa and 700 K. No phase transition occurs over this P-T range. Using the third-order Birch-Murnaghan equation of state (EoS), we fitted the pressure-volume-temperature (P-V-T) data and obtained the zero-pressure bulk modulus K₀ = 138(2) GPa, its pressure derivative K' 0 = 3.0(3), the temperature derivative of the bulk modulus ((∂K/∂T)_P = −0.004(1) GPa/K), and the thermal expansion coefficient at 300 K (α₀ =3.8(5) × 10⁻⁵ K⁻¹), as the zero-pressure unit-cell volume V₀ was fixed at 465.2(2) ų (obtained by a single-crystal XRD experiment at ambient conditions). This study reveals that the bulk moduli of epidote show nonlinear compositional dependence. By discussing the stabilization of epidote and comparing its density with those of other hydrous minerals, we find that epidote, as a significant water transporter in subduction zones, may maintain a metastable state to ∼14 GPa along the coldest subducting slab geotherm and promote slab subduction into the upper mantle while favoring slab stagnation above the 410 km discontinuity. Furthermore, the water released from epidote near 410 km may potentially affect the properties of the 410 km seismic discontinuity.

Epidote是俯冲带中一种典型的含水矿物。在这里，我们报告了在高压下同时进行的天然附子[Ca _1.97 Al _2.15 Fe _0.84（SiO ₄）（Si ₂ O ₇）O（OH）]的基于同步加速器的单晶X射线衍射（XRD）研究。（高P - T）条件达到〜17.7 GPa和700K。在此P - T范围内没有相变发生。使用三阶Birch-Murnaghan状态方程（EoS），我们拟合了压力-体积-温度（P - V - T）数据，并获得了零压力体积模量ķ ₀ = 138（2）GPA，其压力导数K” 0 = 3.0（3），体积弹性模量（（的温度衍生物∂K/∂T）_P = -0.004（1）GPA / K），并且在300 K（热膨胀系数α ₀ = 3.8（5）×10 ^-5 ķ ^-1），作为零压力晶胞体积V ₀定为465.2（2）埃³（通过在环境条件下的单晶XRD实验获得）。这项研究表明，附子的总体模量显示出非线性的成分依赖性。通过讨论附子的稳定性并将其密度与其他含水矿物的密度进行比较，我们发现附子作为俯冲带中重要的水运载体，可沿最冷的俯冲板状地热保持亚稳态至约14 GPa，并促进俯冲。进入上地幔，同时有利于410 km不连续面上方的平板停滞。此外，从410 km附近的附子释放出来的水可能会影响410 km地震不连续性的性质。