The formation and evolution of the Moon’s crust inferred from the Sm-Nd isotopic systematics of highlands rocks

1Lars E.Borg,1William S.Cassata,1Josh Wimpenny,1Amy M.Gaffney,2Charles K.Shearer
Geochimica et Cosmochimica Acta (in Press) Link to Article []
1Nuclear and Chemical Sciences Division, Lawrence Livermore National Laboratory, 7000 East Avenue L-231, Livermore, CA 94550, USA
2Institute of Meteoritics, University of New Mexico, Albuquerque, NM 87131, USA
Copyright Elsevier

Ages determined for magnesian and ferroan anorthosite crustal rock suites overlap, suggesting they formed contemporaneously about 4.3 to 4.5 Ga. A notable exception is the Sm-Nd age previously determined on Mg-suite gabbronorite 67667 which is at least 100 Ma younger than the youngest ferroan anorthosite. New chronologic measurements of 67667 presented here yield concordant Sm-Nd and Rb-Sr mineral isochron ages of 4349 ± 31 Ma and 4368 ± 67 Ma, suggesting the samples is older than previous estimates. Furthermore, a whole rock Sm-Nd isochron of Mg-suite rocks from the Apollo 14, 15, 16, and 17 landing sites yields an age of 4348 ± 25 Ma, indicating that Mg-suite magmatism was widespread and roughly contemporaneous on the lunar nearside. Analysis of Sm-Nd internal isochron ages confirms that Mg-suite magmatism was restricted to a period between about 4.33 and 4.35 Ga at the Apollo 14, 15, 16, and 17 landing sites and was synchronous with magmatism at the Apollo 16 site associated with the ferroan anorthosite suite between 4.35 and 4.37 Ga. Magnesian- and ferroan anorthosite suite rocks with ages younger than ∼4.33 Ga appear to have experienced slow cooling in the deep lunar interior, so that the ages record when the samples cooled below the closure temperature of the Sm-Nd isotopic system and not the time they crystallized.

The ages determined for Mg-suite and ferroan anorthosite suite rocks are concordant with the age determined for the formation of urKREEP of 4350 ± 34 Ma using the Sm-Nd isotopic systematics of 67667 and measurements completed on norite 78238, troctolite 76535, KREEP basalt 15386, and gabbronorite NWA 773. Crystallization ages of Mg-suite and FAS are also concordant with the average of 146Sm-142Nd ages previously determined for the formation of the mare basalt source region of 4333 ± 30 Ma. The similarity of ages for Mg-suite magmatism, ferroan anorthosite suite magmatism, urKREEP formation, and formation of the mare basalt source regions implies the processes that produced these rocks were petrogenetically linked. It also implies that both early-stage and late-stage lunar magma ocean cumulates formed over a relatively short duration of <40 Ma. Late and somewhat rapid solidification of a lunar magma ocean can account for the concordance of ferroan anorthosite suite rocks, urKREEP, and the mare basalt source regions. However, the major and trace element compositions of Mg-suite magmas preclude them from being a primary differentiation product of the lunar magma ocean. Instead, the Mg-suite could be produced as a result of mixing of magma ocean solidification products during density driven overturn occurring immediately after, or perhaps during, solidification of the lunar magma ocean. This scenario not only accounts for the chronology of the various rock suites, but is consistent with the petrogenesis of the Mg-suite that involves the interaction between pre-existing Mg-rich, plagioclase-rich, and urKREEP-rich cumulates of the magma ocean.

Elemental estimation of terrestrial analogues from the CanMars rover field campaign using LiRS: Implications for detecting silica-rich deposits on Mars

Icarus (in Press) Link to Article []
1Centre for Research in Earth and Space Science, York University, 4700 Keele St., Toronto M3J 1P3, Canada
2Department of Mathematics and Statistics, York University, 4700 Keele St., Toronto M3J 1P3, Canada
3Unidad Asociada Universidad de Valladolid-CSIC-CAB, C/Francisco Valles 8, 47151 Boecillo, Valladolid, Spain
4CSIRO Mineral Resources, 26 Dick Perry Ave, Kensington, WA 6151, Australia
5Department of Geography, University of Winnipeg, 515 Portage Ave, Winnipeg, Manitoba R3B 2E9, Canada
6Department of Physics, University of Toronto, 60 St George St, Toronto, ON M5S 1A7, Canada
Copyright Elsevier

As space agencies plan for the continuous deployment of rovers and landers to planetary bodies such as the Moon and Mars, an in-depth, quantitative, and qualitative understanding of the observations is essential. One objective of planetary exploration focuses on planetary geochemistry and biochemistry with an emphasis on the search for possible biosignatures and related minerals. To this end, we present the elemental quantification of samples from the CanMars analogue sample return mission conducted in Hanksville, UT, USA. Measurements were carried out in a laboratory at York University, Canada, using the Laser-induced Breakdown Spectroscopy Raman Sensor (LiRS) instrument- a breadboard for future space concept. A linear Mixture Model (LMM) was used to quantify the abundance of major elements of 10 samples from the resulting Laser-induced Breakdown Spectroscopy LIBS spectra with a calibration set based on the sample mineralogy. We assess the quantification achieved by LiRS and the LMM by error analysis, which resulted in root mean squared error, absolute error, and percentage relative error of less than 1.299 %  ± 0.114% (wt%), 0.959 ± 0.010 (wt%), and 9.613 %  ± 1.914% (of wt%), respectively. The results in question suggest that by complementing information obtained from various sources such as Raman spectroscopy, X-ray diffraction, and Reflectance spectroscopy, the quantification of LIBS may be significantly improved, from which subsequent geochemical inferences may be made. Within the scope of the CanMars analogue mission, these results show an advancement over past results with possible implications for ongoing and future sample return missions such as the OSIRIS-REx and the Mars2020 Perseverance Rover.

Spectral and geological analyses of domes in western Arcadia Planitia, Mars: Evidence for intrusive alkali-rich volcanism and ice-associated surface features

Icarus (in Press) Link to Article []
1Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301, USA
2Planetary Science Institute, 1700 East Ft. Lowell, Suite 106, Tucson, AZ 85719, USA
3Stony Brook University, Department of Geoscience, 255 ESS Building, Stony Brook, NY 11794, USA
Copyright Elsevier

Small-scale domes with circumferential aprons and concentric aureoles in western Arcadia Planitia (34–41°N, 167–179°E) near Tyndall crater were examined using a suite of datasets including CRISM, THEMIS IR, HiRISE, and CTX. Previous studies based primarily on photogeologic evidence suggested that these domes were analogous to terrestrial felsic cryptodomes to extrusive lava domes. The domes have also been examined using CRISM visible/near infrared to short-wave infrared (VNIR-SWIR) reflectance spectra which indicated the presence of ferrous silicate minerals in association with the domes. This study presents further CRISM spectral evidence for 1) high-Ca pyroxene and glass mixtures with, or possibly without, the presence of olivine on the flanks of some domes, 2) 1.3 μm band absorption features consistent with an Fe-bearing plagioclase or possibly a Fe-rich alkali feldspar in more limited occurrences at the base of some domes, 3) spectral convexity between 3.4 and 3.9 μm associated with rocky, light-toned portions on top of some domes which is attributed to the presence of alkali-rich plagioclase or alkali feldspars. New morphologic observations include a possible cinder cone and arcs of light-toned, “brain terrain” material on the pole-facing upper margins of some aprons which, in combination with ice-associated “brain terrain” on light-toned outer aureoles suggests an association with ice. The morphology of an assortment of domes and association with alkali feldspars suggests they represent a continuum from intrusive cryptodomes to flat extrusive domes, potentially of felsic composition although formation from viscous alkali-rich mafic magmas is not precluded.

Reproduction of I‐type cosmic spherules and characterization in an Fe‐Ni‐O system

1Huimin Shao,1Hiroshi Isobe,2Bingkui Miao
Meteoritics & Planetary Science (in Press) Link to Article []
1Department of Earth and Environmental Sciences, Faculty of Advanced Science and Technology, Kumamoto University, Kumamoto, 8608555 Japan
2Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration, Guilin University of Technology, Guilin, 541004 China
Published by arrangement with John Wiley & Sons

The chemical composition and texture of cosmic spherules are influenced by atmospheric conditions and the characteristics of their parent interplanetary particles. The objective of this study was to reproduce I‐type cosmic spherules, which consist mainly of Fe oxide and Fe‐Ni metal, and compare their textural characteristics with those of natural I‐type cosmic spherules. Thus, a series of rapid heating and quenching experiments were performed on free falling iron meteorite powders obtained from Canyon Diablo, in the United States. The experiments were conducted using a high‐temperature furnace with controlled gas flow rates at oxygen fugacities of FMQ + 2.4, FMQ, and FMQ − 2.5 log unit. The resulting Fe‐Ni metal and oxide phases showed the nonequilibrium state of the melted spherules formed during quenching. Two types of magnetite crystals in different orientations were found in iron oxide. As temperatures decreased, the molten metal was oxidized to form immiscible molten iron oxide that then covered the former. As the oxide melt increased at the expense of metal, magnetite began to crystallize from the iron oxide melt, as the liquidus phase, either on the surface or within the melt phase. The characteristics of the run products obtained under different oxygen fugacities were similar to those of natural I‐type cosmic spherules, which have textures and compositions that may contain information regarding the oxygen content of the upper atmosphere. Our study suggests that CO2‐bearing molecules in the atmosphere could form iron oxide with a texture similar to natural I‐type cosmic spherules. During this process, rapid crystallization of magnetite plays an important role in texture formation in disequilibrium states.

Mid‐infrared reflectance spectroscopy of aubrite components

1Andreas Morlok,1Iris Weber,1Aleksandra N. Stojic,2Martin Sohn,1Addi Bischoff,3Dayl Martin,1Harald Hiesinger,4Joern Helbert
Meteoritics & Planetary Science (in Press) Link to Article []
1Institut für Planetologie, Westfälische Wilhelms Universität, Münster, Wilhelm‐Klemm‐Str. 10, Münster, 48149 Germany
2Hochschule Emden/Leer, Constantiaplatz 4, Emden, 26723 Germany
3European Space Agency, Fermi Avenue, Harwell Campus, Didcot, Oxfordshire, OX11 0FD UK
4Institute for Planetary Research, DLR, Rutherfordstrasse 2, Berlin, 12489 Germany
Published by arrangement with John Wiley & Sons

Aubrites Peña Blanca Spring and Norton County were studied in the mid‐infrared reflectance as part of a database for the MERTIS (Mercury Radiometer and Thermal Infrared Spectrometer) instrument on the ESA/JAXA BepiColombo mission to Mercury. Spectra of bulk powder size fractions from Peña Blanca Spring show enstatite Reststrahlen bands (RB) at 9 µm, 9.3 µm, 9.9 µm, 10.4 µm, and 11.6 µm. The transparency feature (TF) is at 12.7 µm, the Christiansen feature (CF) at 8.1–8.4 µm. Micro‐FTIR of spots with enstatite composition in Norton County and Peña Blanca Spring shows four types: Types I and II are similar to the bulk powder spectra but vary in band shape and probably display axis orientation. Type III has characteristic strong RB at 9.2 µm, 10.4 µm, and 10.5 µm, and at 11.3 µm. Type IV is characterized by a strong RB at 10.8−11.1 µm. Types III and IV could show signs of incipient shock metamorphism. Bulk results of this study confirm earlier spectral studies of aubrites that indicate a high degree of homogeneity and probably make the results of this study representative for spectral studies of an aubrite parent body. Spectral types I and II occur in all mineralogical settings (mineral clasts, matrix, melt, fragments in melt vein), while spectral type III was only observed among the clasts, and type IV in the melt. Comparison with surface spectra of Mercury does not obtain a suitable fit, only type IV spectra from quenched impact glass show similarity, in particular the 11 µm feature. Results of this study will be available upon request or via the IRIS database (Münster) and the Berlin Emissivity Database (BED).

A revised shock history for the youngest unbrecciated lunar basalt—Northwest Africa 032 and paired meteorites

1Tatiana Mijajlovic,1Xi Xue,1Erin Walton
Meteoritics & Planetary Science (in Press) Link to Article []
1Department of Physical Sciences, MacEwan University, 10700 104 Ave, Edmonton, Alberta, T5J 2S2 Canada
Published by arrangement with John Wiley & Sons

Northwest Africa (NWA) 032 is an unbrecciated porphyritic basalt found in the Moroccan desert in 1999. Constituent igneous minerals—olivine, pyroxene, and plagioclase—exhibit shock deformation and transformation effects. NWA 032 is among the youngest radiometrically dated sample from the Moon, with concordant Sm‐Nd and Rb‐Sr ages of 2.947 ± 0.016 Ga and 2.931 ± 0.092, respectively, representing the timing of igneous crystallization. We present the first comprehensive study of shock metamorphism in NWA 032, with a focus on the structural state of fine‐grained plagioclase feldspar, shock deformation in olivine and pyroxene, and the microtexture and mineralogy of shock melts. Micro‐Raman spectroscopy, optical properties, and electron imaging confirm that plagioclase in this meteorite has been shock amorphized, which, for calcic plagioclase (An80‐90), requires shock pressures on the order of ~25–27 GPa. Shock pressures in this range are accompanied by a postshock temperature increase <200 °C. Shock deformation in olivine and pyroxene phenocrysts comprises undulose extinction to weak mosaicism, irregular fractures, polysynthetic mechanical twinning in pyroxene, and development of planar fractures in olivine. The shock effects in mafic minerals constrain the upper limit of shock in NWA 032 to have been <30 GPa. Shock melt in NWA 032 has quenched to glass of basaltic composition, representing localized in situ melting of igneous minerals by shearing along lithological boundaries to form shock veins and shock impedance contrasts to form isolated pockets of shock melt. These melts quench‐crystallized olivine and pyroxene during the pressure release (<14 GPa). Using recent experimental data on shock amorphization of feldspars, coupled with constraints on the formation of metastable minerals associated with shock melt, we have revised the shock pressure experienced by paired meteorites NWA 10597, NWA 4734, and LaPaz Icefield 02205/02224/0226/02436/03632/04841. These largely unbrecciated, basaltic meteorites experienced an equilibration shock pressure on the order of ~22–25 GPa, constrained by partial amorphization of precursor igneous bytownite. Our results are consistent with crater pairing and ejection in a single impact cratering event.

Ordinary chondrite shock stage quantification using in situ 2‐D X‐ray diffraction of olivine

1,2Alexandra N. Rupert,1,2Phil J.A. McCausland,1,2Roberta L. Flemming
Meteoritics & Planetary Science (in Press) Link to Article []
1Department of Earth Sciences, Western University, London, Ontario, N6A 5B7 Canada
2Institute for Earth and Space Exploration, Western University, London, Ontario, N6A 5B7 Canada
Published by arrangement with John Wiley & Sons

Ordinary chondrites record shock metamorphism resulting from hypervelocity collisions on small bodies, and underpin the petrographic assessment of shock stage, a scale of progressive stages of shock metamorphism from S1 (unshocked) to S7 (shock melted). In this work, olivine grains in 11 L and LL chondrites (S1–S5) were investigated in thin section and hand sample using in situ two‐dimensional X‐ray diffraction (2‐D XRD). Olivine grains were measured under a 300 µm X‐ray beam for multiple lattice reflections, by measuring diffracted streak length along the chi (χ) dimension (Debye ring dimension), to examine their strain‐related mosaicity. Olivine strain‐related mosaicity was observed to increase with greater shock deformation, with more complex multi‐peak streaks apparent at higher shock levels. The full width at half maximum (FWHMχ) of the simple peak shapes along χ was measured to quantify petrographic shock stage for comparison with that described optically. The average FWHMχ values for simple peaks in olivine show an increase with increasing shock stage: S1 (0.44°± 0.06°), S2 (0.58°± 0.11°), S3 (0.67°± 0.15°), S4 (0.76°± 0.13°), and S5 (0.86°± 0.12°). This method complements optical petrographic methods and offers a ±1 shock stage accuracy in determining shock stage. In particular, 2‐D XRD analysis of strain‐related mosaicity allows quantitative analysis of shock stage in shock‐darkened samples that are difficult to work with petrographically, and for hand samples without need for thin section preparation.

Explosive Shaped Projectors for Forming High-Velocity Compact Elements

1,2,3,4Gerasimov, S.I.,1Malyarov, D.V.,2Sirotkina, A.G.,1Kapinos, S.A.,1,4Kalmykov, A.P.,1Knyazev, A.S.
Combustion, Explosion and Shock Waves 56, 486-493 Link to Article [DOI: 10.1134/S0010508220040139]
1All-Russian Research Institute of Experimental Physics (VNIIEF), Russian Federal Nuclear Center, Sarov, 607188, Russian Federation
2Sarov State Physics and Technical Institute, Department of the National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Sarov, 607186, Russian Federation
3Alekseev Nizhny Novgorod State Technical University (NNSTU), Nizhny Novgorod, 603950, Russian Federation
4Institute for Problems in Mechanical Engineering, Russian Academy of Sciences, Nizhny Novgorod, 603024, Russian Federation

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Formation of hexagonal NaAl3Si3O11 (NAS) phase, the Na end-member of hexagonal CaAl4Si2O11 (CAS) phase, near 23 GPa above 2373 K in the compositions of NaAl3Si3O11 and NaAlSi3O8

1Zhou, Y.,1,2Irifune, T.
Physics Chemistry of Minerals 47, 37 Link to Article [DOI: 10.1007/s00269-020-01106-6]
1Geodynamics Research Center, Ehime University, Matsuyama, 790-8577, Japan
2Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo, 152-8550, Japan

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Best Fit for Complex Peaks (BFCP) in Matlab® for quantitative analysis of in situ 2D X-Ray diffraction data and Raman spectra

1,2Li, Y.,1,2McCausland, P.J.A.,1,2Flemming, R.L.
Computers and Geoscience 144, 104572 Link to Article [DOI: 10.1016/j.cageo.2020.104572]
1Department of Earth Sciences, Western University, London, ON N6A 5B7, Canada
2Institute for Earth and Space Exploration, Western University, London, ON N6A 5B7, Canada

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