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Title: A Cr 3+ luminescence study of natural topaz Al 2SiO 4(F,OH) 2 up to 60 GPa

Abstract

Topaz [Al 2SiO 4(F,OH) 2] is a subduction-related mineral that is found in metasediments and has a large pressure and temperature stability field. Here, we use luminescence spectroscopy of Cr 3+ to probe the Al site in topaz at pressures up to ~60 GPa, which corresponds to a depth of ~1400 km in the Earth. This technique allows us to probe all three unique Al environments (i.e., [AlO 4(OH) 2] 7–, [AlO 4(F) 2] 7–, and [AlO4OH,F]7–) simultaneously under high pressure. We find that the R-line luminescence from all three Al environments shift linearly to longer wavelength to ~40 GPa. Above ~40 GPa, they shift nonlinearly and begin to flatten out at ~48 GPa, with a pressure shift of ~0 cm –1/GPa from ~48–55 GPa. Our results, combined with previous high-pressure single-crystal X-ray diffraction studies to ~45 GPa, strongly indicate that there is a change in the compression mechanism in topaz above ~40 GPa. Furthermore, our high-pressure room-temperature results show that the metastable persistence of topaz on compression represents one of the most extreme cases among tetrahedrally coordinated silicates.

Authors:
ORCiD logo [1];  [2]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  2. Univ. of California, Santa Cruz, CA (United States)
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1573158
Report Number(s):
LLNL-JRNL-772914
Journal ID: ISSN 0003-004X; 963785
Grant/Contract Number:  
AC52-07NA27344
Resource Type:
Accepted Manuscript
Journal Name:
American Mineralogist
Additional Journal Information:
Journal Volume: 104; Journal Issue: 11; Journal ID: ISSN 0003-004X
Publisher:
Mineralogical Society of America
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Topaz; High-pressure; Cr3+luminescence; nesosilicates

Citation Formats

O'Bannon, III, Earl F., and Williams, Quentin. A Cr3+ luminescence study of natural topaz Al2SiO4(F,OH)2 up to 60 GPa. United States: N. p., 2019. Web. doi:10.2138/am-2019-7079.
O'Bannon, III, Earl F., & Williams, Quentin. A Cr3+ luminescence study of natural topaz Al2SiO4(F,OH)2 up to 60 GPa. United States. doi:10.2138/am-2019-7079.
O'Bannon, III, Earl F., and Williams, Quentin. Fri . "A Cr3+ luminescence study of natural topaz Al2SiO4(F,OH)2 up to 60 GPa". United States. doi:10.2138/am-2019-7079.
@article{osti_1573158,
title = {A Cr3+ luminescence study of natural topaz Al2SiO4(F,OH)2 up to 60 GPa},
author = {O'Bannon, III, Earl F. and Williams, Quentin},
abstractNote = {Topaz [Al2SiO4(F,OH)2] is a subduction-related mineral that is found in metasediments and has a large pressure and temperature stability field. Here, we use luminescence spectroscopy of Cr3+ to probe the Al site in topaz at pressures up to ~60 GPa, which corresponds to a depth of ~1400 km in the Earth. This technique allows us to probe all three unique Al environments (i.e., [AlO4(OH)2]7–, [AlO4(F)2]7–, and [AlO4OH,F]7–) simultaneously under high pressure. We find that the R-line luminescence from all three Al environments shift linearly to longer wavelength to ~40 GPa. Above ~40 GPa, they shift nonlinearly and begin to flatten out at ~48 GPa, with a pressure shift of ~0 cm–1/GPa from ~48–55 GPa. Our results, combined with previous high-pressure single-crystal X-ray diffraction studies to ~45 GPa, strongly indicate that there is a change in the compression mechanism in topaz above ~40 GPa. Furthermore, our high-pressure room-temperature results show that the metastable persistence of topaz on compression represents one of the most extreme cases among tetrahedrally coordinated silicates.},
doi = {10.2138/am-2019-7079},
journal = {American Mineralogist},
number = 11,
volume = 104,
place = {United States},
year = {2019},
month = {11}
}

Journal Article:
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This content will become publicly available on November 1, 2020
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