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Coupled hydrogen and fluorine incorporation in garnet: New constraints from FTIR, ERDA, SIMS, and EPMA

Mosenfelder, Jed L. and von der Handt, Anette and Withers, Anthony C. and Bureau, Hélène and Raepsaet, Caroline and Rossman, George R. (2022) Coupled hydrogen and fluorine incorporation in garnet: New constraints from FTIR, ERDA, SIMS, and EPMA. American Mineralogist, 107 (4). pp. 587-602. ISSN 0003-004X. doi:10.2138/am-2021-7880.

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It is well known that some garnet compositions can incorporate hydrogen and/or fluorine at levels up to several wt%. However, accurate measurement of these elements can be difficult at trace to minor concentration levels, so they are frequently ignored in routine chemical analysis. Furthermore, the mechanisms of H incorporation are still under debate, and only one mechanism for F substitution is commonly considered. We employed infrared spectroscopy (FTIR), elastic recoil detection analysis (ERDA), secondary ion mass spectrometry (SIMS), and electron probe microanalysis (EPMA) to measure H and F concentrations and constrain incorporation mechanisms in ten grossular garnets. We also present SIMS data for 11 spessartine and two andradite garnets. Three grossular garnets were measured with ERDA to obtain an infrared integral molar absorption coefficient (ε_i) for H₂O of 13 470 L/(mol·cm²). Grossular H₂O and F concentrations range from 0.017 to 0.133 wt% and 0.012 to 0.248 wt%, respectively. Correlations between ¹⁶OH and ¹⁹F and interpretation of FTIR spectra prompt us to consider various coupled substitutions of H and F for Si, which can explain some high-frequency IR absorption bands that have been attributed previously to “hydrogrossular clusters” (variably sized clusters in which 4H substitute for Si) or to inclusions of hydrous minerals. A strong correlation between ¹⁶OH and ¹⁹F in spessartine and similar high-frequency IR bands implies a similar role for H-F substitution. Coupled H-F substitution is also probably relevant to some andradite-rich garnets, rare pyrope from the Dora Maira massif, and some synthetic garnets. Improvements in analytical methods for trace to minor H and F open up more possibilities for using these elements to calculate the activities of H₂O and F-species in fluids that were in equilibrium with garnet-bearing phase assemblages, as well as constraining the recycling of these elements into the mantle via study of xenoliths.

Item Type:Article
Related URLs:
URLURL TypeDescription
von der Handt, Anette0000-0003-1975-9909
Withers, Anthony C.0000-0003-4835-4281
Bureau, Hélène0000-0002-5506-5122
Raepsaet, Caroline0000-0001-8965-6089
Rossman, George R.0000-0002-4571-6884
Additional Information:© 2022 Mineralogical Society of America. Manuscript received November 2, 2020; Manuscript accepted March 10, 2021; Manuscript handled by Anne Peslier. The manuscript was improved by helpful reviews from Andrew Locock, Jörg Hermann, and an anonymous reviewer. We also thank Yunbin Guan for assistance with SIMS analyses and John Beckett for help operating the gas-mixing 1 atm furnace. Campbell Bridges, Peter Flusser, Robert Gaal, Peter Keller, William Larson, Gary Novak, and Julius Petsch are thanked for providing garnet samples that were used in the work. Financial support for this research is gratefully acknowledged from NSF grants EAR-0947956 and EAR-1322082 to George Rossman, EAR-1347908 to Jed Mosenfelder, NASA 80NSSC19K0959 to Marc Hirschmann, the Gordon and Betty Moore Foundation, and the White Rose Foundation.
Funding AgencyGrant Number
Gordon and Betty Moore FoundationUNSPECIFIED
White Rose FoundationUNSPECIFIED
Subject Keywords:Fluids and aqueous geochemistry, geochemistry, mineralogy, infrared spectroscopy, Mössbauer spectroscopy
Issue or Number:4
Record Number:CaltechAUTHORS:20220504-861041200
Persistent URL:
Official Citation:Jed L. Mosenfelder, Anette von der Handt, Anthony C. Withers, Hélène Bureau, Caroline Raepsaet, George R. Rossman; Coupled hydrogen and fluorine incorporation in garnet: New constraints from FTIR, ERDA, SIMS, and EPMA. American Mineralogist 2022; 107 (4): 587–602. doi:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:114587
Deposited By: Tony Diaz
Deposited On:05 May 2022 23:30
Last Modified:05 May 2022 23:30

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