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The compressibility and expansivity of anglesite (PbSO4) have been measured at high pressure up to 21.6 GPa and high temperature up to 700 K using in situ angle-dispersive X-ray diffraction and diamond anvil cell. The third-order Birch-Murnaghan equation of state (III-BM-EoS) was used to analyze the pressure-volume (P-V) data of PbSO4. We obtained the bulk modulus K0 = 59(1) GPa, and its pressure derivative K0′ = 5.3(4), respectively. Using Holland-Powell thermal EoS to fit the temperature-volume (T-V) data, the thermal expansion coefficient α0 = 4.59(2) × 10− 5 K− 1 for PbSO4 was also derived. Simultaneously, the ambient-pressure axial compressibilities (βa0 = 1.79(4) × 10− 3 GPa− 1, βb0 = 1.75(5) × 10− 3 GPa− 1, βc0 = 2.12(4) × 10− 3 GPa− 1) and axial thermal expansivities (αa0 = 1.23(4) × 10− 5 K− 1, αb0 = 1.93(2) × 10− 5 K− 1, and αc0 = 1.43(1) × 10− 5 K− 1) along a-axis, b-axis and c-axis were derived at 300 K, respectively. Furthermore, the potential influencing factors (e.g., the effective size of M2+ cation, polarizability and electronegativity) on the bulk moduli of barite-type (belonging to Pbnm space group) sulfates (anglesite, barite, and celestine) were discussed. We found that the polarizability might be the most important factor. Finally, the anisotropic linear compressibility and thermal expansivity in barite-type sulfates were also discussed, respectively. [ABSTRACT FROM AUTHOR]

The equation of state and stability of topaz at high-pressure/high-temperature conditions have been investigated by in situ synchrotron X-ray diffraction (XRD) and Raman spectroscopy in this study. No phase transition occurs on topaz over the experimental pressure–temperature (P-T) range. The pressure–volume data were fitted by the third-order Birch–Murnaghan equation of state (EoS) with the zero-pressure unit–cell volume V0 = 343.86 (9) Å3, the zero-pressure bulk modulus K0 = 172 (3) GPa, and its pressure derivative K'0 = 1.3 (4), while the obtained K0 = 155 (2) GPa when fixed K'0 = 4. In the pressure range of 0–24.4 GPa, the vibration modes of in-plane bending OH-groups for topaz show non-linear changes with the increase in pressure, while the other vibration modes show linear changes. Moreover, the temperature–volume data were fitted by Fei's thermal equation with the thermal expansion coefficient α300 = 1.9 (1) × 10−5 K−1 at 300 K. Finally, the P-T stability of topaz was studied by a synchrotron-based single-crystal XRD at simultaneously high P-T conditions up to ~10.9 GPa and 700 K, which shows that topaz may maintain a metastable state at depths above 370 km in the upper mantle along the coldest subducting slab geotherm. Thus, topaz may be a potential volatile-carrier in the cold subduction zone. It can carry hydrogen and fluorine elements into the deep upper mantle and further affect the geochemical behavior of the upper mantle. [ABSTRACT FROM AUTHOR]

The high-temperature unit-cell parameters and volumes of three Li-bearing tourmalines (elbaite (CC05), elbaite (CC11) and schorl (D54)) have been determined through in situ synchrotron radiation angle-dispersive X-ray diffraction experiments. No phase transition of these tourmalines has been observed up to the maximum temperature in this study. The volumetric thermal expansion coefficients of the three Li-bearing tourmalines are determined from the measured unit-cell volumes at high temperatures with Berman's equations. And the elbaite (CC05) has the least volumetric thermal expansion coefficients among the three Li-bearing tourmalines in this study. Furthermore, the axial thermal expansion behavior of these Li-bearing tourmalines is also fitted with "linearized" Berman's equation. The results show that Li-bearing tourmalines has an intense anisotropic axial thermal expansivity, where the c -axis has a larger axial thermal expansion coefficient than a -axis. The potential factors influencing on the thermal expansivity and the anisotropic axial thermal expansivities of Li-bearing tourmalines are further discussed. • Temperature dependence of the unit-cell parameters of Li-bearing tourmalines, established using synchrotron-based XRD. • No phase transition of these tourmalines has been observed up to the maximum temperature in this study. • Li-bearing tourmaline has an intense anisotropic axial thermal expansivity. • The different compositions at Y site may affect the volumetric thermal expansion coefficients of Li-bearing tourmalines. [ABSTRACT FROM AUTHOR]