Characterizing the degree of aqueous alteration in a fresh sample of Mukundpura CM chondrite fall using ATR-FTIR and TGA

1A. Dixit,2R. P. Tripathi,3Sudhanshu Kumar,3Mohd. Azaj Ansari,3K. Sreenivas
Meteoritics & Planetary Science (in Press) Link to Article []
1Department of Physics, Indian Institute of Technology, Jodhpur, 342037 India
278, BGKT Extension Scheme, New Pali Road, Jodhpur, 342005 India
3Department of Physics and Astrophysics, University of Delhi, Delhi, 110007 India
Published by arrangement with John Wiley & Sons

Fourier transform infrared (FTIR) measurements on immediately collected Mukundpura show the typical feature for phyllosilicates around 10 μm, corresponding to Si-O stretching mode in silicate, and its broadness signifies the amorphous or poorly crystalline silicates. The absence of the 11.2 μm feature (a characteristic of anhydrous silicate olivine) and the weight loss observed in thermogravimetric analysis (TGA) imply aggressive aqueous alteration, which resulted in phyllosilicate formation at the expense of primary anhydrous silicates. It is consistent with Mössbauer spectra, showing the presence of both Fe2+ and Fe3+ in phyllosilicates, but no characteristic peak for olivine is observed, suggesting the major fraction of primary silicates are aggressively altered due to the presence of water on the parent body, and now major lithology must be highly altered. TGA measurements were carried on it (i) within 24 h and (ii) after 30 months of its fall. In both cases, the weight loss was ∼10% in the 400–770 °C temperature range, confirming the absence of any environmental impact on the water bound to the hydrated clay in Mukundpura samples. Appreciable weight loss in 400–770 °C indicated the presence of hydrated clay that corroborated FTIR measurements and ruled out any thermal event suffered by its postaqueous alteration, consistent with amorphous or poorly crystalline silicate phase observed in FTIR. When we couple the results of the present study and already reported results by our group on the same Mukundpura fragment, it is inferred that our sample has suffered a very high degree of aqueous alteration on the parent body. The fingerprint ratios, which are extensively used to correlate or assign petrological subgroup, are FeO/SiO2, hydrous silicate/anhydrous silicates, and MgO/FeO, which are either considered alone or in combination, and for Mukundpura, the values for these ratios are 1.05, 7.2, and ∼0.60, respectively. These values indicate that the major lithology of Mukundpura fresh fragment must be assigned as CM2.1.

Geochemistry of lunar meteorite Northwest Africa 11962 and its potential source region/crater in the Procellarum KREEP terrane

1Andreas Bechtold,1Toni Schulz,1Wencke Wegner,1Dieter Mader,2Christian Patterer,1Christian Koeberl
Meteoritics & Planetary Science (in Press) Open Access Link to Article []
1Department of Lithospheric Research, University of Vienna, UZA 2, Josef-Holaubek-Platz 2, 1090 Vienna, Austria
2Motrada Handels GmbH, Salesianergasse 31/11, 1030 Vienna, Austria
Published by arrangment with John Wiley & Sons

Lunar meteorite Northwest Africa (NWA) 11962 is a regolith breccia with a diverse range of mineral and lithic clasts. For the present study, major and trace element contents and selected isotopic compositions were determined on a homogenized bulk powder of NWA 11962 by instrumental neutron activation analysis, thermal ionization mass spectrometry, and inductively coupled plasma mass spectrometry. The chemical composition of the sample points toward an origin of the meteorite from within the Procellarum KREEP terrane (PKT). Samarium-Nd and Rb-Sr isotopic compositions and concentrations show a similarity to those of Apollo 15 soils and KREEP basalt. Highly siderophile element (HSE) abundances and ratios, as well as the Re/Os isotopic system, are often used as tracers of different impactor types. The 187Os/188Os and 187Re/188Os isotopic ratios are within the range of ordinary chondrites, yet some of the siderophile element and highly siderophile element ratios are comparable to those of iron meteorites. Using Fe, Th, and Ti abundances of lunar surface regolith, measured by the Lunar Prospector gamma-ray spectrometer, we attempt to constrain potential lunar source regions for NWA 11962. By matching these possible source regions with coordinates of recently (<1 Ma) formed lunar impact craters (so-called lunar cold spots), we localized a potential source crater of NWA 11962 at the western rim of the PKT close to Sinus Medii.

Trace element partitioning between olivine and melt in lunar basalts

1Sha Chen,1Peng Ni,1Youxue Zhang,2Joel Gagnon
American Mineralogist 107, 1519-1531 Link to Article []
1Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, Michigan 48109, U.S.A.
2School of the Environment, University of Windsor, Windsor, Ontario N9B 3P4, Canada
Copyright: The Mineralogical Society of America

Mineral/melt partition coefficients have been widely used to provide insights into magmatic
processes. Olivine is one of the most abundant and important minerals in the lunar mantle and mare
basalts. Yet, no systematic olivine/melt partitioning data are available for lunar conditions. We report
trace element partition data between host mineral olivine and its melt inclusions in lunar basalts.
Equilibrium is evaluated using the Fe-Mg exchange coefficient, leading to the choice of melt inclusionhost olivine pairs in lunar basalts 12040, 12009, 15016, 15647, and 74235. Partition coefficients of
21 elements (Li, Mg, Al, Ca, Ti, V, Cr, Mn, Fe, Co, Y, Zr, Nb, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu)
were measured. Except for Li, V, and Cr, these elements show no significant difference in olivine-melt
partitioning compared to the data for terrestrial samples. The partition coefficient of Li between olivine
and melt in some lunar basalts with low Mg# (Mg# < 0.75 in olivine, or < ~0.5 in melt) is higher than published data for terrestrial samples, which is attributed to the dependence of DLi on Mg# and the lack of literature DLi data with low Mg#. The partition coefficient of V in lunar basalts is measured to be 0.17 to 0.74, significantly higher than that in terrestrial basalts (0.003 to 0.21), which can be explained by the lower oxygen fugacity in lunar basalts. The significantly higher DV can explain why V is less enriched in evolved lunar basalts than terrestrial basalts. The partition coefficient of Cr between olivine and basalt melt in the Moon is 0.11 to 0.62, which is lower than those in terrestrial settings by a factor of ~2. This is surprising because previous authors showed that Cr partition coefficient is independent of fO2. A quasi-thermodynamically based model is developed to correlate Cr partition coefficient to olivine and melt composition and fO2. The lower Cr partition coefficient between olivine and basalt in the Moon can lead to more Cr enrichment in the lunar magma ocean, as well as more Cr enrichment in mantle-derived basalts in the Moon. Hence, even though Cr is typically a compatible element in terrestrial basalts, it is moderately incompatible in primitive lunar basalts, with a similar degree of incompatibility as V based on partition coefficients in this work, as also evidenced by the relatively constant V/Cr ratio of 0.039 ± 0.011 in lunar basalts. The confirmation of constant V/Cr ratio is important for constraining concentrations of Cr (slightly volatile and siderophile) and V (slightly siderophile) in the bulk silicate Moon.

Estimating kaolinite crystallinity using near-infrared spectroscopy: Implications for itsgeology on Earth and Mars

1Maxime Pineau,2Maximilien Mathian,1,3Fabien Baron,1Benjamin Rondeau,1Laetitia Le Deit,2Thierry Allard,1Nicolas Mangold
American Mineralogist 107, 1453-1469 Open Access Link to Article []
1Laboratoire de Planétologie et Géodynamique, UMR CNRS 6112, Université de Nantes, Université d’Angers, Nantes, France
2Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, UMR CNRS 7590, Sorbonne Université, Paris, France

3Institut de Chimie des Milieux et Matériaux de Poitiers, UMR CNRS 7285, Université de Poitiers, Poitiers, France
Copyright: The Mineralogical Society of America

Kaolinite is an Al-rich phyllosilicate commonly observed on Earth as a product of the chemical
weathering of aluminosilicates. It has also been detected on the martian surface by orbital remote
sensing observations. While the determination of the geological processes of formation of terrestrial
kaolinite (i.e., hydrothermal activity, continental surface weathering, diagenesis) involves the coupling of field observation and multiple laboratory measurements, only geomorphology and associated
minerals are generally available to determine their geological origin on Mars. Kaolinite crystallinity
depends on many physicochemical parameters reflecting its conditions of crystallization. To determine if the near-infrared (NIR) spectral signature of kaolinite enables estimation of its crystallinity
and furthermore if this method can be used to identify the geological processes involved in kaolinite
formation, we carried out an in-depth analysis of NIR spectra of reference terrestrial kaolinites that
formed in various geological contexts. We calculated second and third derivatives for each spectrum
to highlight subtle variations in the spectral properties of kaolinite. This allowed the identification of
27 spectral contributions for the 4500 and 7000 cm−1 Al-OH-related regions of absorption bands. The
position shifts and shape variations of these spectral contributions were intimately linked to variations
of crystallinity, which was qualitatively estimated using Hinckley and Liétard XRD (dis)order indices.
The results obtained show that the NIR signature of kaolinite is influenced by the stacking disorder of
layers that has some influence on the vibrations of the interfoliar and inner Al-OH groups. Our study
also confirms that: (1) well-ordered kaolinites are not restricted to hydrothermal deposits; (2) kaolinites
from a similar sedimentary or pedogenetic context often display contrasting degrees of crystalline
order; and (3) poorly ordered kaolinites are more likely to have a sedimentary or pedogenetic origin.
Finally, this work highlights that obtaining spectra with sufficient spectral resolution could help to
estimate the crystallinity of kaolinite and, in the best cases, its geological origin, both on Earth and
Mars, especially with in situ NIR measurements.

The interplay between twinning and cation inversion in MgAl2O4-spinel: Implications for anebular thermochronometer

1,2Venkateswara Rao Manga,1,2Krishna Muralidharan,1,2Thomas J. Zega
American Mineralogist 107, 1470 – 1476 Link to Article []
1Lunar and Planetary Laboratory, University of Arizona, 1629 E. University Boulevard, Tucson, Arizona 85721, U.S.A.
2Department of Materials Science and Engineering, University of Arizona, 1235 E. James E. Rogers Way, Tucson, Arizona 85721, U.S.A.
Copyright: The Mineralogical Society of America

We report a first-principles-based thermodynamic investigation of the interplay between cation
inversion and twinning in MgAl2O4 spinel (MAS). We examine the atomic-scale structure of (111)
twins and characterize the local octahedral and tetrahedral distortions. We observe that the asymmetric
nature of polyhedral distortions about the (111) twin plane causes anisotropy in cation inversion energies
near the planar fault. The predicted enthalpies and entropies of inversion reveal that in comparison to
the Kagome layer, the anti-site occupancies of Al and Mg, i.e., cation inversion, on the mixed-cationlayer near the twin boundary are more favorable and stable in the entire range of temperature of twin
stability. Structurally, such a stable inversion is necessitated by the minimization in the polyhedral
distortions, especially by the octahedral distortion, which exhibits a reduction of four orders of magnitude relative to the polyhedra with no inversion. The fundamental understanding obtained on the
thermodynamics of the twin-cation inversion interplay in conjunction with the kinetics of inversion
was used as a basis for developing a thermochronometer for deducing the temperature of twinning
in MAS. This work serves as an important steppingstone for experimental characterization of MAS
structures within a host of Earth and planetary materials. In the case of the latter, our results enable
the use of planar faults, such as twins, as important markers for deducing the physical and chemical
landscape that MAS experienced in its evolution and transport within the solar protoplanetary disk.

Low-temperature thermal properties of iron meteorites

1Christopher S. Noyes,2Guy. J. Consolmagno,2Robert J. Macke,3,4Daniel T. Britt,1Cyril P. Opeil
Meteoritics & Planetary Science (in Press) Link to Article []
1Department of Physics, Boston College, 140 Commonwealth Avenue, Chestnut Hill, Massachusetts, 02467 USA
2Vatican Observatory, Vatican City, V-00120 Vatican City State
3Department of Physics, University of Central Florida, 4111 Libra Dr, Orlando, Florida, 32816 USA
4Center of Lunar and Asteroid Surface Science, 12354 Research Pkwy, Suite 214, Orlando, Florida, 32826 USA
Published by arrangement with John Wiley & Sons

We have measured the thermal conductivity and specific heat capacity of subsamples from four iron meteorites with nickel concentrations between 5% and 8% (Agoudal, Canyon Diablo, Muonionalusta, and Sikhote-Alin) at temperatures between 5 and 300 K. From these, we have calculated their thermal diffusivity and thermal inertia values across this temperature range. For comparison, we also measured subsamples from two L chondrites (NWA 11038 and NWA 11344) at the same time, using the same methods. The thermal diffusivity results of the irons show a relatively constant value for T > 100 K with a characteristic low-temperature maxima at ∼5 K for the iron meteorites; by contrast, the diffusivities of the L chondrites fell by a factor of two over this range and reached low-temperature maxima at ∼20 K. Thermal inertia values show a crossover behavior, with a strong increase in thermal inertia as temperatures drop below 55 K and a less dramatic change at higher temperatures. Our new diffusivity and inertia values cover a wider range of temperatures than previous literature data for iron meteorites. They also provide a useful ground truth in understanding remotely sensed thermal inertias of potentially metal-rich asteroids, including 16 Psyche, target of the NASA Psyche mission.

The influence of variable oxygen fugacity on the source depths of lunar high-titanium ultramafic glasses

1Megan E.Guenther,1Stephanie M.Brown Krein,1Timothy L.Grove
Geochimica et Cosmochimica Acta (in Press) Link to Article []
1Massachusetts Institute of Technology, Department of Earth, Atmospheric and Planetary Sciences 54-1212, 77 Massachusetts Ave, Cambridge, MA 02139, United States
Copyright Elsevier

We present the results of high pressure, high temperature multiple saturation experiments at variable oxygen fugacity ( conditions (IW+1.5 and IW-2.1) on three lunar high titanium ultramafic glasses: the Apollo 17 Orange glass (A17O, 9.1 wt. % TiO2), the Apollo 15 Red glass (A15R, 13.8 wt. % TiO2), and the Apollo 14 Black glass (A14B, 16.4 wt. % TiO2). We performed experiments in graphite ( = IW+1.5) and iron ( = IW-2.1) capsules. The experimentally determined multiple saturation points (MSPs) in graphite capsules are 2.5 GPa and ∼1530℃ (A17O), 1.3 GPa and ∼1350℃ (A15R), and 1.55 GPa and ∼1425℃ (A14B). In iron, we found MSPs of 3.3 GPa and ∼1565℃ (A17O), 2.8 GPa and ∼1490℃ (A15R), and 4.0 GPa and ∼1540℃ (A14B). These results, when combined with previous experiments on the lunar ultramafic glasses, indicate that the increase in the pressure of multiple saturation is linearly proportional to the TiO2 content of the melt , R2 = 0.93, RMSE = 0.2 GPa). The high depths of melting correlated with the lowest conditions are hard to reconcile with buoyancy constraints on these iron and titanium rich magmas. In addition, measurements of on the orange glass as well as the presence of iron blebs in the glasses suggest that the glasses were reduced during eruption. To reconcile buoyancy constraints with estimates, we present a model in which the high titanium magmas experienced higher conditions at their source, but underwent subsequent reduction at shallow depths (4-52 km) just prior to their eruption. In this model, we can then further bracket the depth of melting to be from the minimum multiple saturation pressure in graphite to the deepest depth at which the magmas are buoyant: assuming the Hess and Parmentier (1995) post overturn cumulate mantle, the depths of melting range from ∼550-770 km for the A17O glass, ∼260-490 km for the A15R glass, and ∼320-350 km for the A14B glass.

Modeling the production of submicroscopic iron in the lunar highlands

1,2A.P.Jordan,3M.L.Shusterman,4C.J.Tai Udovicic
Icarus (in Press) Link to Article []
1Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH, USA
2Solar System Exploration Research Virtual Institute, NASA Ames Research Center, Moffett Field, CA, USA
3School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA
4Northern Arizona University, Flagstaff, AZ, USA
Copyright Elsevier

Micrometeoroid impacts, solar wind bombardment, and dielectric breakdown driven by solar energetic particles all potentially alter the optical properties of the lunar regolith by creating submicroscopic metallic iron (smFe0), which includes both nanophase (<33nm) and microphase (>33nm) iron. We create a simple model that describes the time-dependent accumulation of optically active smFe0 in the lunar highlands. Our model synthesizes recent analyses of how space weathering processes form smFe0-bearing agglutinates and rims on soil grains and how impact gardening controls the exposure time of these grains. It successfully reproduces the results of a prior analysis of the formation of smFe0 in the highlands, particularly in regard to nanophase iron, showing that there is consistency among diverse analyses of Apollo samples and of orbital observations. We find that the results of our model are not consistent with the solar wind directly forming smFe0 (although the solar wind may play a role in optical maturation via hydrogen implantation). Our model results are consistent with smFe0 in the lunar highlands being created mainly by micrometeoroid impacts, with a possible contribution from dielectric breakdown weathering.

Siderophile volatile element inventory in lunar magmatic rocks and mantle sources

1Philipp Gleißner,1Julie Salme,1Harry Becker
Earth and Planetary Science Letters 593, 117680 Link to Article []
1Freie Universität Berlin, Institut für Geologische Wissenschaften, Malteserstr. 74-100, 12249 Berlin, Germany
Copyright Elsevier

Elevated water contents in various lunar materials have invigorated the discussion on the volatile content of the lunar interior and on the extent to which the volatile element inventory of lunar magmatic rocks is controlled by volatility and degassing. Abundances of moderately volatile and siderophile elements can reveal insights into lunar processes such as core formation, late accretion and volatile depletion. However, previous assessments relied on incomplete data sets and data of variable quality. Here we report mass fractions of the siderophile volatile elements Cu, Se, Ag, S, Te, Cd, In, and Tl in lunar magmatic rocks, analyzed by state-of-the-art isotope dilution-inductively coupled plasma mass spectrometry. The new data enable us to disentangle distribution processes during the formation of different magmatic rock suites and to constrain mantle source compositions. Mass fractions of Cu, S, and Se in mare basalts and magnesian suite norites clearly correlate with indicators of fractional crystallization. Similar mass fractions and fractional crystallization trends in mafic volcanic and plutonic rocks indicate that the latter elements are less prone to degassing during magma ascent and effusion than proposed previously. The latter processes predominate only for specific elements (e.g., Tl, Cd) and complementary enrichments of these elements also occur in some brecciated highland rocks. A detailed comparison of elements with different affinities to metal or sulfide and gas phase reveals systematic differences between lunar magmatic rock suites. The latter observation suggests a predominant control of the variations of S, Se, Cu, and Ag by mantle source composition instead of late-stage magmatic degassing. New estimates of mantle source compositions of two low-Ti mare basalt suites support the notion of a lunar mantle that is strongly depleted in siderophile volatile elements compared to the terrestrial mantle.

Compositional and spectroscopic investigation of three ungrouped carbonaceous chondrites

1Mehmet Yesiltas,2Yoko Kebukawa,3Timothy D. Glotch,4Michael Zolensky,4Marc Fries,5Namik Aysal,5Fatma S. Tukel
Meteoritics & Planetary Science (in Press) Link to Article []
1Faculty of Aeronautics and Space Sciences, Kirklareli University, Kirklareli, 39100 Turkey
2Faculty of Engineering, Yokohama National University, 240-8501 Yokohama, Japan
3Department of Geosciences, Stony Brook University, Stony Brook, New York, 11790 USA
4Astromaterials Research and Exploration Science, Johnson Space Center, NASA, Houston, Texas, 77058 USA
5Department of Geological Engineering, Istanbul University-Cerrahpasa, Istanbul, 34320 Turkey
Published by arrangement with John Wiley & Sons

Ungrouped carbonaceous chondrites are not easily classified into one of the well-established groups due to compositional/petrological differences and geochemical anomalies. Type 2 ungrouped carbonaceous chondrites represent a very small fraction of all carbonaceous chondrites. They can potentially represent different aspects of asteroids and their regolith material. By conducting a multitechnique investigation, we show that Queen Alexandra Range (QUE) 99038 and Elephant Moraine (EET) 83226 do not resemble type 2 carbonaceous chondrites. QUE 99038 exhibits coarse-grained matrix, Fe-rich rims on olivines, and an apparent lack of tochilinite, suggesting that QUE 99038 has been metamorphosed. Its polyaromatic organic matter structures closely resemble oxidized CV3 chondrites. EET 83226 exhibits a clastic texture with high porosity and shows similarities to CO3 chondrites. It consists of numerous large chondrules with fine-grained rims that are often fragmented and discontinuous and set within matrix, suggesting a formation mechanism for the rims in a regolith environment. The kind of processes that can result in such chemical compositions as in QUE 99038 and EET 83226 is currently not fully known and clearly presents a conundrum. Tarda is a highly friable carbonaceous chondrite with close resemblance to Tagish Lake (ungrouped C2 chondrite). It comprises different types of chondrules (some with Fe-rich rims), framboid magnetite, sulfides, carbonates, and phyllosilicate- and carbon-rich matrix, and is consistent with being an ungrouped C2 chondrite.