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A Synchrotron Mössbauer Spectroscopy Study of a Hydrated Iron-Sulfate at High Pressures

Perez, Tyler and Finkelstein, Gregory J. and Pardo, Olivia and Solomatova, Natalia V. and Jackson, Jennifer M. (2020) A Synchrotron Mössbauer Spectroscopy Study of a Hydrated Iron-Sulfate at High Pressures. Minerals, 10 (2). Art. No. 146. ISSN 2075-163X. doi:10.3390/min10020146.

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Szomolnokite is a monohydrated ferrous iron sulfate mineral, FeSO₄·H₂O, where the ferrous iron atoms are in octahedral coordination with four corners shared with SO4 and two with H₂O groups. While somewhat rare on Earth, szomolnokite has been detected on the surface of Mars along with several other hydrated sulfates and is suggested to occur near the surface of Venus. Previous measurements have characterized the local environment of the iron atoms in szomolnokite using Mössbauer spectroscopy at a range of temperatures and 1 bar. Our study represents a step towards understanding the electronic environment of iron in szomolnokite under compression at 300 K. Using a hydrostatic helium pressure-transmitting medium, we explored the pressure dependence of iron’s site-specific behavior in a synthetic szomolnokite powdered sample up to 95 GPa with time-domain synchrotron Mössbauer spectroscopy. At 1 bar, the Mössbauer spectrum is well described by two Fe²⁺-like sites and no ferric iron, consistent with select conventional Mössbauer spectra evaluations. At pressures below 19 GPa, steep gradients in the hyperfine parameters are most likely due to a structural phase transition. At 19 GPa, a fourth site is required to explain the time spectrum with increasing fractions of a low quadrupole splitting site, which could indicate the onset of another transition. Above 19 GPa we present three different models, including those with a high- to low-spin transition, that provide reasonable scenarios of electronic environment changes of the iron in szomolnokite with pressure. We summarize the complex range of Fe²⁺ spin transition characteristics at high-pressures by comparing szomolnokite with previous studies on ferrous-iron bearing phases.

Item Type:Article
Related URLs:
URLURL TypeDescription
Finkelstein, Gregory J.0000-0001-7343-7527
Pardo, Olivia0000-0003-3964-9272
Solomatova, Natalia V.0000-0002-2331-3427
Jackson, Jennifer M.0000-0002-8256-6336
Additional Information:© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ( Received: 21 December 2019; Accepted: 4 February 2020; Published: 8 February 2020. We are thankful to Wolfgang Sturhahn, Rachel Morrison, and Thomas S. Toellner for helpful discussions. We are thankful to Bob Liebermann for handling our manuscript and to three anonymous reviewers for their helpful feedback and suggestions. We thank the Mr. and Mrs. Larson for their contribution to the Summer Undergraduate Research Fellowship program at Caltech, which supported part of this work. N.V.S. was partly funded by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (Grant Agreement Number 681818–IMPACT). We thank the W.M. Keck Institute for Space Studies and NSF-CSEDI-EAR-1161046 for support of this research. Operations at Sector 3 (APS) and beamline 12.2.2 (ALS) are partially supported by COMPRES. This research used resources of the Advanced Photon Source and of the Advanced Light Source, which are DOE Office of Science User Facilities under contracts DE-AC02-06CH11357 and DE-AC02-05CH11231, respectively. Author Contributions: Conceptualization, J.M.J.; methodology, G.J.F., T.P., and J.M.J.; validation, T.P., G.J.F., O.P., N.V.S., and J.M.J.; formal analysis, T.P.; investigation, T.P. and J.M.J.; writing—original draft preparation, T.P., G.J.F., N.V.S., and J.M.J.; writing—review and editing, T.P. and J.M.J.; resources, data curation, and funding acquisition, J.M.J. All authors have read and agree to the published version of the manuscript. The authors declare no conflict of interest.
Group:Keck Institute for Space Studies, Seismological Laboratory
Funding AgencyGrant Number
Caltech Summer Undergraduate Research Fellowship (SURF)UNSPECIFIED
European Research Council (ERC)681818
Keck Institute for Space Studies (KISS)UNSPECIFIED
Consortium for Materials Properties Research in Earth Sciences (COMPRES)UNSPECIFIED
Department of Energy (DOE)DE-AC02-06CH11357
Department of Energy (DOE)DE-AC02-05CH11231
Subject Keywords:iron-sulfates; hydrous phases; szomolnokite; high-pressure; synchrotron Mössbauer spectroscopy; spin-transition
Issue or Number:2
Record Number:CaltechAUTHORS:20200226-150304224
Persistent URL:
Official Citation:Perez, T.; Finkelstein, G.J.; Pardo, O.; Solomatova, N.V.; Jackson, J.M. A Synchrotron Mössbauer Spectroscopy Study of a Hydrated Iron-Sulfate at High Pressures. Minerals 2020, 10, 146
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:101595
Deposited By: Tony Diaz
Deposited On:26 Feb 2020 23:12
Last Modified:16 Nov 2021 18:04

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