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Topaz, a Potential Volatile-Carrier in Cold Subduction Zone: Constraint from Synchrotron X-ray Diffraction and Raman Spectroscopy at High Temperature and High Pressure TEXT SIZE: A A A
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 volumeV(0)= 343.86 (9) angstrom(3), the zero-pressure bulk modulus K-0= 172 (3) GPa, and its pressure derivativeK'(0)= 1.3 (4), while the obtained K-0= 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 alpha(300)= 1.9 (1) x 10(-5)K(-1)at 300 K. Finally, theP-Tstability of topaz was studied by a synchrotron-based single-crystalXRDat simultaneously highP-Tconditions up to similar 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.

Publication name

 MINERALS Volume: 10 Issue: 9 Article Number: 780 DOI: 10.3390/min10090780 Published: SEP 2020


 Huang, Shijie; Xu, Jingui; Chen, Chunfa; Kuang, Yunqian; Fan, Dawei; Zhou, Wenge; Ma, Maining

Corresponding author(s) 

 ZHOU Wenge 
 Chinese Acad Sci, Inst Geochem, Key Lab Hightemp & Highpressure Lab High Temp & H, Guiyang 550002, Peoples R China.
 MA Maining
 Univ Chinese Acad Sci, Coll Earth & Planetary Sci, Key Lab Computat Geodynam, Beijing 100049, Peoples R China.

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