^1,2,6Ranjan Sarkar, ³Ed Cloutis, ³Daniel Applin, ³Nathalie Turenne, ⁴Daniel Mège, ⁵Andreas Beinlich, ⁵Stanley A. Mertzman
Icarus (in Press) Link to Article [DOI: 10.1016/j.icarus.2026.117282]
¹Max Planck Institute for Solar System Research, Göttingen, Germany
²Indian Institute of Technology, Kharagpur, India
³Department of Geography, University of Winnipeg, Winnipeg, MB, Canada R3B 2E9
⁴Centrum Badań Kosmicznych Polskiej Akademii Nauk (CBK PAN), ul. Bartycka 18a, 00-716, Warszawa, Poland
⁵Institut für Geologische Wissenschaften, Freie Universität Berlin, Kaiserswerther Str. 16-18, 14195 Berlin, Germany.
⁶Department of Earth and Environment, Franklin and Marshall College, Lancaster, PA 17604, USA.
Copyright Elsevier

Listvenites are extensively carbonated ultramafic rocks such as peridotites and serpentinites that commonly containing carbonates (magnesite, dolomite), quartz, and often the accessory mineral fuchsite—a green, chromium-bearing variety of muscovite. Listvenites form distinctive yellow-orange ridges in areal views due to their mechanically-resistant carbonate-silica mineralogy and iron oxidation. They form when an ultramafic protolith comes into contact with CO₂-rich fluids and undergoes a progressive replacement of the Fe/Mg-bearing olivines and pyroxenes or serpentinites into increasingly carbonate-rich assemblages, and ultimately to carbonate-quartz rocks. We analyzed listvenite samples from the Atlin area, British Columbia, Canada using a variety of analytical techniques, including X-ray diffraction (XRD), X-ray fluorescence (XRF), wet chemistry (WC), visible-near infrared (VNIR) reflectance spectroscopy (0.35-2.5 μm), and Raman spectroscopy. VNIR and Raman spectroscopies were able to successfully identify all major mineral phases through their diagnostic absorption (VNIR) or emission (Raman) features. We found that listvenite composition is readily derivable from VNIR reflectance and Raman spectra, with fuchsite providing a diagnostic signature in VNIR spectra due to its unique Cr³⁺ absorption bands that remain detectable even at low concentrations. These findings establish a spectroscopic framework for identifying listvenites in remote sensing applications, relevant for exploration of Solar System bodies, particularly Mars, where such carbonated ultramafic rocks can produce H₂ and CH₄, and may preserve biosignatures and might indicate past habitable conditions associated with their low-temperature formation.

^1,2Oleg I. Siidra, ³Artem S. Borisov, ⁴Victoria A. Ginga, ¹Veronika R. Abdulina, ⁵Dmitri O. Charkin, ⁶Anatoly V. Kasatkin, ³Astrid Holzheid, ⁴Annette Setzer, ⁷Vladimir N. Bocharov
Icarus (in Press) Link to Article [DOI: 10.1016/j.icarus.2026.117275]
¹Department of Crystallography, St. Petersburg State University, University Emb. 7/9, 199034 St. Petersburg, Russia
²Kola Science Center, Russian Academy of Sciences, Apatity 184200, Murmansk Region, Russia
³Institut für Geowissenschaften der Universität Kiel, Olshausenstr. 40, D-24098 Kiel, Germany
⁴Felix Bloch Institute for Solid-State Physics, Leipzig University, Linnestrasse 5, D-04103 Leipzig, Germany
⁵Chemistry Department, Moscow State University, Vorobievy Gory 1-3, Moscow 119991 Russia
⁶Fersman Mineralogical Museum of the Russian Academy of Sciences, Leninsky Prospekt 18-2, 119071 Moscow, Russia
⁷Geomodel Resource Center, St. Petersburg State University, University Emb. 7/9, 199034 St. Petersburg, Russia
Copyright Elsevier

Copiapite-group minerals are among the most common hydrated iron sulfate minerals in a variety of geological environments on Earth. They are also believed to be widespread on the Martian surface. The transformation and stability of the copiapite-group minerals are examined in this study using a diverse array of methods, including low- (LT) and high-temperature (HT) single-crystal X-ray diffraction (SCXRD), LT- and HT-powder X-ray diffraction (PXRD), vacuum powder X-ray diffraction, HT-Raman spectroscopy, magnetization and heat capacity measurements. The research is conducted over a broad temperature range (−175–740 °C) and under vacuum (~ 600 Pa) conditions that are partially similar to those found on the Martian surface (from −153 °C to over 20 °C and ~ 600 Pa). The obtained results indicate that aluminocopiapite, (Al0.54Fe3+0.13)Σ0.67Fe3+4(SO4)6(OH)2(H2O)20, is unstable under low vacuum conditions and undergoes a structural transition to a post-aluminocopiapite phase, (Al0.63Fe3+0.04)Σ0.67Fe3+4(SO4)6(OH)2(H2O)12.44 with a significantly lower water and iron content and a higher aluminum content. Schwertmannite, Fe3+16O16(OH)9.6(SO4)3.2·10H2O is formed as a film/shell on the crystal surface of post-aluminocopiapite via a single crystal-to-single crystal (SC-SC) topotactic transformation and exsolution. After 14 days of exposure to air, the post-aluminocopiapite crystal with schwertmannite shell undergoes a reversible process, reverting to its initial aluminocopiapite state. A closely analogous transformation, involving partial dehydration, was observed for copiapite, Fe2+Fe3+4(SO4)6(OH)2(H2O)20, demonstrating that this behavior is a general feature of the copiapite group.
It is therefore unlikely that copiapite-group minerals would exist on the surface of Mars and in comparable extraterrestrial environments in their initial form. Instead, under Mars surface conditions with low vacuum, post-copiapites and schwertmannite may be among the most common minerals in hydrated iron sulfate mineral associations. This is relevant for decoding past geo- and climatic environments on Mars and for selecting the conditions for the return of intact samples collected by rovers to Earth.

¹Jillian Kirk, ¹Myriam Telus, ¹Pranvera Hyseni, ¹Fatima Jorge-Chavez, ²Vanessa Mendoza, ³Steven J. Desch, ⁴Dale Burns, ⁵Steven Simon
Icarus (in Press) Open Access Link to Article [DOI: 10.1016/j.icarus.2026.117263]
¹University of California Santa Cruz, Department of Earth and Planetary Sciences, 1156 High Street, Santa Cruz, 95064, CA, USA
²Western Washington University, Geology Department, 516 High St, Bellingham, 98225, WA, USA
³Arizona State University, School of Earth and Space Exploration, 781 Terrace Mall, Tempe, 85287, AZ, USA
⁴Stanford University, Department of Geological Sciences, 450 Jane Stanford Way, Stanford, 94305, CA, USA
⁵University of New Mexico, Institute of Meteoritics, 221 Yale Blvd NE MSC03 2050, Albuquerque, 87131, NM, USA
Copyright Elsevier

Chondrules are small igneous particles that formed in the protoplanetary disk and make up the bulk of chondrites. Chondrule rims offer insights into the composition of dust in the solar nebula and the conditions and heating mechanisms associated with chondrule formation. High-resolution elemental mapping of pristine CO3 chondrite thin sections revealed igneous chondrule rims enriched in manganese, a moderately volatile element (MVE), which is sensitive to thermal processing. These chondrule rims have not previously been characterized, in part due to their small thicknesses (
30
m). Characterization of Mn-rich rims in CO3 chondrites reveals that this enrichment exists in a variety of textures, some of which are associated with non-igneous fine-grained rims, while many clearly formed from a melt. Mn-rich pyroxenes in CO3 chondrule rims are also enriched in Na, K, and Cr, as compared to pyroxene in host chondrules (i.e., chondrules hosting the Mn-rich rims) and no-rim chondrules (chondrules without Mn-rich rims). These enrichments seem to be the result of nebular processing of chondrules as opposed to parent-body processing, as enrichments do not correlate with petrologic subtypes. Pyroxene with similar enrichments in these elements occur within igneous chondrule rims seen in CR chondrites, indicating that these rims may have formed across different locations and times in the nebula. Previous studies have suggested that MVE enrichment of chondrule rims occurred during interaction with MVE-enriched nebular gas. Our results could support an alternative scenario involving accretion of MVE-enriched dust onto solidified chondrules, which subsequently experienced varying degrees of thermal processing, possibly facilitated by a planetesimal or planetary embryo bow shock, resulting in MVE-enriched chondrule rims. Future work is needed to validate this idea. This study highlights the potential role of outgassing planetesimals and/or planetary embryos as a source of MVE-rich dust in the solar nebula.