¹Takayuki Ishii et al. (>10)*
¹Department of Chemistry, Gakushuin University, Mejiro, Toshima-ku, Tokyo 171-8588, Japan
*Find the extensive, full author and affiliation list on the publishers website

We determined phase relations in FeCr2O4 at 12–28 GPa and 800–1600 °C using a multi-anvil apparatus. At 12–16 GPa, FeCr2O4 spinel (chromite) first dissociates into two phases: a new Fe2Cr2O5 phase + Cr2O3 with the corundum structure. At 17–18 GPa, the two phases combine into CaFe2O4-type and CaTi2O4-type FeCr2O4 below and above 1300 °C, respectively. Structure refinements using synchrotron X-ray powder diffraction data confirmed the CaTi2O4-structured FeCr2O4 (Cmcm), and indicated that the Fe2Cr2O5 phase is isostructural to a modified ludwigite-type Mg2Al2O5 (Pbam). In situ high-pressure high-temperature X-ray diffraction experiments showed that CaFe2O4-type FeCr2O4 is unquenchable and is converted into another FeCr2O4 phase on decompression. Structural analysis based on synchrotron X-ray powder diffraction data with transmission electron microscopic observation clarified that the recovered FeCr2O4 phase has a new structure related to CaFe2O4-type. The high-pressure phase relations in FeCr2O4 reveal that natural FeCr2O4-rich phases of CaFe2O4- and CaTi2O4-type structures found in the shocked Suizhou meteorite were formed above about 18 GPa at temperature below and above 1300 °C, respectively. The phase relations also suggest that the natural chromitites in the Luobusa ophiolite previously interpreted as formed in the deep-mantle were formed at pressure below 12–16 GPa.

Reference
Takayuki T et al. (2014) High-pressure phase transitions in FeCr2O4 and structure analysis of new post-spinel FeCr2O4 and Fe2Cr2O5 phases with meteoritical and petrological implications. American Mineralogist 99, 1788-1797
Link to Article [doi:10.2138/am.2014.4736]

Copyright: The Mineralogical Society of America

¹Patricia L. Clay, ²Brian O’Driscoll, ³Brian G.J. Upton, ¹Henner Busemann
¹School of Earth, Atmospheric and Environmental Sciences, The University of Manchester, Manchester M13 9PL, U.K.
²School of Physical and Geographical Sciences, Keele University, Keele ST5 5BG, U.K.
³School of Geosciences, The University of Edinburgh, Edinburgh EH9 3JW, U.K.

Djerfisherite is a K-Cl-bearing sulfide that is present in both ultra-reduced extraterrestrial enstatite meteorites (enstatite chondrites or achondrites) and reduced terrestrial alkaline intrusions, kimberlites, ore deposits, and skarns. Major element chemistry of two terrestrial occurrences of djerfisherite (from the Ilímaussaq and Khibina alkaline igneous suites) and three extraterrestrial examples of djerfisherite have been determined and combined with petrographic characterization and element mapping to unravel three discrete modes of djerfisherite formation. High Fe/Cu is characteristic of extraterrestrial djerfisherite and low Fe/Cu is typical of terrestrial djerfisherite. Ilímaussaq djerfisherite, which has high-Fe contents (~55 wt%) is the exception. Low Ni contents are typical of terrestrial djerfisherite due to preferential incorporation of Fe and/or Cu over Ni, but Ni contents of up to 2.2 wt% are measured in extraterrestrial djerfisherite. Extensive interchange between K and Na is evident in extraterrestrial samples, though Na is limited (<0.15 wt%) in terrestrial djerfisherite. We propose three setting-dependent mechanisms of djerfisherite formation: primitive djerfisherite as a product of nebula condensation in the unequilibrated E chondrites; formation by extensive K-metasomatism in Khibina djerfisherite; and as a product of primary “unmixing” due to silicate-sulfide immiscibility for Ilímaussaq djerfisherite. There are several important reasons why a deeper understanding of the petrogenesis of this rare and unusual mineral is valuable: (1) its anomalously high K-contents make it a potential target for Ar-Ar geochronology to constrain the timing of metasomatic alteration; (2) typically high Cl-contents (~1.1 wt%) mean it can be used as a valuable tracer of fluid evolution during metasomatic alteration; and (3) it may be a potential source of K and magmatic Cl in the sub-continental lithospheric mantle (SCLM), which has implications for metal solubility and the generation of ore deposits.

Reference
Clay PL, O’Driscoll B, Upton GJ, Busemann H (2014) Characteristics of djerfisherite from fluid-rich, metasomatized alkaline intrusive environments and anhydrous enstatite chondrites and achondrites. American Mineralogist 99, 1683-1693
Link to Article [doi:10.2138/am.2014.4700]

Copyright: The Mineralogical Society of America

¹Axel Wittmann, ¹Randy L. Korotev, ¹Bradley L. Jolliff, ²Thomas J. Lapen, ³Anthony J. Irving
¹Department of Earth and Planetary Sciences, Washington University in St. Louis, Campus Box 1169, 1 Brookings Drive, St. Louis, Missouri 63130-4899, U.S.A.
²Department of Earth and Atmospheric Sciences, University of Houston, 4800 Calhoun Road, Houston, Texas 77004, U.S.A.
³Department of Earth and Space Sciences, University of Washington, 4000 15th Avenue NE, Seattle, Washington 98195, U.S.A.

This study explores the petrogenesis of Shişr 161, an immature lunar regolith breccia meteorite with low abundances of incompatible elements, a feldspathic affinity, and a significant magnesian component. Our approach was to identify all clasts >0.5 mm in size in a thin section, characterize their mineral and melt components, and reconstruct their bulk major and minor element compositions. Trace element concentrations in representative clasts of different textural and compositional types indicate that the clast inventory of Shişr 161 is dominated by impact melts that include slowly cooled cumulate melt rocks with mafic magnesian mineral assemblages. Minor exotic components are incompatible-element-rich melt spherules and glass fragments, and a gas-associated spheroidal precipitate. Our hypothesis for the petrologic setting of Shişr 161 is that the crystallized melt clasts originate from the upper ~1 km of the melt sheet of a 300 to 500 km diameter lunar impact basin in the Moon’s feldspathic highlands. This hypothesis is based on size requirements for cumulate impact melts and the incorporation of magnesian components that we interpret to be mantle-derived. The glassy melts likely formed during the excavation of the melt sheet assemblage, by an impact that produced a >15 km diameter crater. The assembly of Shişr 161 occurred in a proximal ejecta deposit of this excavation event. A later impact into this ejecta deposit then launched Shişr 161 from the Moon. Our geochemical modeling of remote sensing data combined with the petrographic and chemical characterization of Shişr 161 reveals a preferred provenance on the Moon’s surface that is close to pre-Nectarian Riemann-Fabry basin.
The petrogenesis of impact basin melt rocks in lunar meteorite Shişr 161

Reference
Wittmann A, Korotev RL, Jolliff BL, Lapen TJ, Irving AJ (2014) The petrogenesis of impact basin melt rocks in lunar meteorite Shişr 161. American Mineralogist 99, 1626-1647
Link to Article [doi:10.2138/am.2014.4837]

Copyright: The Mineralogical Society of America

¹Karly M. Pitman, ¹Eldar Z. Noe Dobrea, ²Corey S. Jamieson, ³James B. Dalton III,³William J. Abbey, ¹Emily C.S. Joseph

¹Planetary Science Institute, 1700 E. Fort Lowell Road, Suite 106, Tucson, Arizona 85719, U.S.A.
²SETI Institute, 189 Bernardo Avenue, Suite 100, Mountain View, California 94043, U.S.A.
³Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109, U.S.A.

Visible and near-infrared wavelength (VNIR, λ = 0.35–5 μm) laboratory diffuse reflectance spectra and corresponding optical functions (real and imaginary refractive indices) for several iron sulfates (natural K- and Na-jarosite, szomolnokite, rhomboclase) are presented. On Mars, jarosite has been identified in Meridiani Planum, Mawrth Vallis, Melas Chasma, and Eridania Basin; szomolnokite has been found as distinct layers at Columbus Crater and as outcrops at Juventae Chasma, and rhomboclase has been identified at Gusev Crater. Constraining the mineralogy and chemistry (Fe- vs. Mg-rich) of the sulfates on Mars may contribute to our understanding of the environmental and aqueous conditions present on Mars during their formation. The data presented here will help to constrain the mineralogy, abundance, and distribution of sulfates on the martian surface, which will lead to improvements in understanding the pressure, temperature, and humidity conditions and how active frost, groundwater, and atmospheric processes once were on Mars.

Reference
Pitman KM, Dobrea EZN, Jamieson CS, Dalton III JB, Abbey WJ, Joseph ECS (2014) Reflectance spectroscopy and optical functions for hydrated Fe-sulfates. American Mineralogist 99, 1593-1603
Link to Article [doi:10.2138/am.2014.4730]

Copyright: The Mineralogical Society of America

^1,2Janice L. Bishop, ^1,2Richard Quinn, ³M. Darby Dyar
¹SETI Institute, Carl Sagan Center, Mountain View, California, 94043, U.S.A.
²Space Science and Astrobiology Division, NASA-Ames Research Center, Moffett Field, California, 94035, U.S.A.
³Department of Astronomy, Mount Holyoke College, South Hadley, Massachusetts, 01075, U.S.A.

K+, Na+, Ca2+, Mg2+, Fe2+, Fe3+, and Al3+ perchlorate salts were studied to provide spectral and thermal data for detecting and characterizing their possible presence on Mars. Spectral and thermal analyses are coordinated with structural analyses to understand how different cations and different hydration levels affect the mineral system. Near-infrared (NIR) spectral features for perchlorates are dominated by H2O bands that occur at 0.978–1.01, 1.17–1.19, 1.42–1.48, 1.93–1.99, and 2.40–2.45 μm. Mid-IR spectral features are observed for vibrations of the tetrahedral ClO4− ion and occur as reflectance peaks at 1105–1130 cm−1 (~8.6–9 μm), 760–825 cm−1 (~12–13 μm), 630 cm−1 (~15.9 μm), 460–495 (~20–22 μm), and 130–215 (~50–75 μm). The spectral bands in both regions are sensitive to the type of cation present because the polarizing power is related to the band center for many of the spectral features. Band assignments were confirmed for many of the spectral features due to opposing trends in vibrational energies for the ClO4− and H2O groups connected to different octahedral cations. Differential scanning calorimetry (DSC) data show variable patterns of water loss and thermal decomposition temperatures for perchlorates with different cations, consistent with changes in spectral features measured under varying hydration conditions. Results of the DSC analyses indicate that the bond energies of H2O in perchlorates are different for each cation and hydration state. Structural parameters are available for Mg perchlorates (Robertson and Bish 2010) and the changes in structure due to hydration state are consistent with DSC parameters and spectral features. Analyses of changes in the Mg perchlorate structures with H2O content inform our understanding of the effects of hydration on other perchlorates, for which the specific structures are less well defined. Spectra of the hydrated Fe2+ and Fe3+ perchlorates changed significantly upon heating to 100 °C or measurement under low-moisture conditions indicating that they are less stable than other perchlorates under dehydrated conditions. The perchlorate abundances observed by Phoenix and MSL are likely too low to be identified from orbit by CRISM, but may be sufficient to be identifiable by a VNIR imager on a future rover.

Reference
Bishop JL, Quinn R, Dyar MD (2014) Spectral and thermal properties of perchlorate salts and implications for Mars. American Mineralogist 99, 1580-1592
Link to Article [doi:10.2138/am.2014.4707]

Copyright: The Mineralogical Society of America

¹Guillermo Lopez-Reyes, ^2,3,4Pablo Sobron, ²Catherine Lefebvre, ¹Fernando Rull

¹Unidad Asociada UVA-CSIC-Centro de Astrobiología, C/ Francisco Valles 8, 47151, Boecillo, Spain
²Space Science and Technology, Canadian Space Agency, 6767 Rte. de l’Aéroport, St. Hubert, Quebec J3Y 8Y9, Canada
³MalaUva Labs, 822 Allen Avenue A, St. Louis, Missouri 63104, U.S.A.
⁴SETI Institute, 189 Bernardo Avenue 100, Mountain View, California 94043, U.S.A.

We have built three multivariate analysis mathematical models based on principal component analysis (PCA), partial least squares (PLS), and artificial neural networks (ANNs) to detect sulfate minerals in geological samples from laser Raman spectral data. We have critically assessed the potential of the models to automatically detect and quantify the abundance of selected Ca-, Fe-, Na-, and Mg-sulfates in binary mixtures. Samples were analyzed using a laboratory version of the Raman laser spectrometer (RLS) instrument onboard the European Space Agency 2018 ExoMars mission. Our results show that PCA and PLS, can be used to quantify to some extent the abundance of mineral phases. PCA separated hydrated from dehydrated mixtures and classified mixtures depending on the phase abundances. PLS provided relatively good calibration curves for these mixtures. Upon spectral pre-processing, ANNs provided the most precise qualitative and quantitative results. The detection of mineral phases was 100% accurate for pure samples, as was for binary mixtures where the abundance of mineral phases was >10%. The outputs of the ANN were proportional to the phase abundance of the mixture, thus demonstrating the ability of ANNs to quantify the abundance of different phases without the need for calibration. Taken together, our findings demonstrate that multivariate analysis provides critical qualitative and quantitative information about the studied sulfate minerals.

Reference
Lopez-Reyes G, Sobron P, Lefebvre C, Rull F (2014) Multivariate analysis of Raman spectra for the identification of sulfates: Implications for ExoMars. American Mineralogist 99,1570-1579
Link to Article [doi:10.2138/am.2014.4724]

Copyright: The Mineralogical Society of America

^1,2 Kaveh Pahlevan

¹Department of Geology and Geophysics, Yale University, New Haven, CT, USA
²Observatoire de la Côte d’Azur, Nice, France

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

Reference
Pahlevan K (2014) Isotopes as tracers of the sources of the lunar material and processes of lunar origin. Philosophical Transactions of the Royal Society A 13,372,2024
Link to Article [doi:10.1098/rsta.2013.0257]

¹Norman H. Sleep, ²Kevin J. Zahnle, ²Roxana E. Lupu
¹Department of Geophysics, Stanford University, Stanford, CA 94305, USA
² NASA Ames Research Center, Moffett Field, CA 94035, USA

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

Reference
Sleep N, Zahnle KJ, Lupu RE (2014) Terrestrial aftermath of the Moon-forming Impact. Philosophical Transactions of the Royal Society A 13, 372, 2024
Link to Article [doi:10.1098/rsta.2013.0172]

¹J. Salmon, ¹R. M Canup
¹ Department of Space Studies, Southwest Research Institute, 1050 Walnut Street, Suite 300, Boulder, CO 80302, USA

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

Reference
Salmon J, Canup RM (2014) Accretion of the Moon from non-canonical discs. Philosophical Transactions of the Royal Society A 13, 372, 2024
Link to Article [doi: 10.1098/rsta.2013.0256]

¹William R. Ward
¹Planetary Science Directorate, Southwest Research Institute, Boulder, CO 80027, USA

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

Reference
Ward WR (2014) On the evolution of the protolunar disc. Philosophical Transactions of the Royal Society A 13,372, 2024
Link to Article [doi: 10.1098/rsta.2013.0250]