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High-pressure Raman and Nd (super 3+) luminescence spectroscopy of bastnaesite-(REE)CO (sub 3) F

Cara E. Vennari and Quentin Williams
High-pressure Raman and Nd (super 3+) luminescence spectroscopy of bastnaesite-(REE)CO (sub 3) F
American Mineralogist (October 2019) 104 (10): 1389-1401

Abstract

Bastnasite-(Ce), a rare earth element (REE) bearing carbonate (Ce,La,Y,Nd,Pr)CO (sub 3) F, is one of the most common REE-bearing minerals and has importance from both economic and geologic perspectives due to its large REE concentration. It also provides an example of the structural interplay between carbonate groups and fluorine ions, as well as the complex bonding properties of rare earth elements. We report Raman vibrational and Nd (super 3+) luminescence ( (super 4) F (sub 3/2) --> (super 4) I (sub 9/2) , (super 4) F (sub 3/2) --> (super 4) I (sub 11/2) , and (super 4) F (sub 5/2) + (super 2) H (sub 9/2) --> (super 4) I (sub 9/2) ) spectra of natural bastnasite-(Ce) to 50 GPa at 300 K. Two phase transitions are observed under compression. Bastnasite-I remains the stable phase up to 25 GPa, where it undergoes a subtle phase transition to bastnasite-II. This is likely produced by a change in symmetry of the carbonate ion. Bastnasite-II transforms to bastnasite-III at approximately 38 GPa, as demonstrated by changes in the luminescence spectra. This second transition is particularly evident within the (super 4) F (sub 3/2) --> (super 4) I (sub 9/2) luminescent transitions, and it appears that a new rare earth element site is generated at this phase change. This transition is also accompanied by modest changes in both the Raman spectra and two sets of luminescent transitions. Despite these transformations, the carbonate unit remains a stable, threefold-coordinated unit throughout this pressure range, with a possible increase in its distortion. Correspondingly, the rare-earth element site(s) appears to persist in quasi-ninefold coordination as well, implying that the general bonding configuration in bastnasite is at least metastable over a approximately 30% compression range. All pressure-induced transitions are reversible, with some hysteresis, reverting to its ambient pressure phase on decompression.


ISSN: 0003-004X
EISSN: 1945-3027
Coden: AMMIAY
Serial Title: American Mineralogist
Serial Volume: 104
Serial Issue: 10
Title: High-pressure Raman and Nd (super 3+) luminescence spectroscopy of bastnaesite-(REE)CO (sub 3) F
Affiliation: University of California Santa Cruz, Department of Earth and Planetary Sciences, Santa Cruz, CA, United States
Pages: 1389-1401
Published: 201910
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 43
Accession Number: 2019-097889
Categories: General geophysics
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 6 tables
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Abstract, copyright, Mineralogical Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 2019
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