标题：Thermoelasticity and stability of natural epidote at high pressure and high temperature: Implications for water transport during cold slab subduction
摘要：AbstractEpidote is a typical hydrous mineral in subduction zones. Here, we report a synchrotron-based single-crystal X-ray diffraction (XRD) study of natural epidote [Ca1.97Al2.15Fe0.84(SiO4)(Si2O7)O(OH)] under simultaneously high pressure-temperature (highP-T) conditions to ~17.7 GPa and 700 K. No phase transition occurs over thisP-Trange. 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 modulusK0 = 138(2) GPa, its pressure derivativeK0' = 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 volumeV0was fixed at 465.2(2) Å3(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.Graphical abstractDisplay OmittedHighlights•Epidote may remain metastable in the upper mantle along a relatively cold subducting slab geotherm.•Epidote is denser than other common hydrous minerals and promotes slab subduction into the upper mantle.•The water released from epidote near 410 km may potentially affect the properties of the 410 km seismic discontinuity.
关键词：KeywordsenEpidoteHydrous mineralSubduction zoneHigh-pressure and high-temperatureSingle-crystal X-ray diffraction
