^1,2Zoltán Váci,¹Carl B. Agee,²Christopher D. K. Herd,^2,3Erin Walton,⁴Oliver Tschauner,¹Karen Ziegler,⁵Vitali B. Prakapenka,⁵Eran Greenberg,⁴Sylvia Monique‐Thomas
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13479]
¹Department of Earth and Planetary Sciences, Institute of Meteoritics, University of New Mexico, Albuquerque, New Mexico, 87106 USA
²Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta, T6G 2E3 Canada
³Department of Earth and Planetary Sciences, MacEwan University, Edmonton, Alberta, T5J 4S2 Canada
⁴Department of Geoscience, University of Nevada, Las Vegas, Las Vegas, Nevada, 89154 USA
⁵GSECARS, Argonne National Laboratory, Lemont, Illinois, 60439 USA
Published by arrangement with John Wiley & Sons

Hydrous alteration of olivine macrocrysts in a Martian olivine phyric basalt, NWA 10416, and a terrestrial basalt from southern Colorado are examined using SEM, EPMA, TEM, and µXRD techniques. The olivines in the meteorite contain linear nanotubes of hydrous material, amorphous areas, and fluid dissolution textures quite distinct from alteration identified in other Martian meteorites. Instead, they bear resemblance to terrestrial deuteric alteration features. The presence of the hydrous alteration phase Mg‐laihunite within the olivines has been confirmed by µXRD analysis. The cores of the olivines in both Martian and terrestrial samples are overgrown by unaltered rims whose compositions match those of a separate population of groundmass olivines, suggesting that the core olivines are xenocrysts whose alteration preceded crystallization of the groundmass. The terrestrial sample is linked to deep crustal metasomatism and the “ignimbrite flare‐up” of the Oligocene epoch. The comparison of the two samples suggests the existence of an analogous relatively water‐rich magmatic reservoir on Mars.

^1,2Naoya Imae,¹Makoto Kimura
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13491]
¹National Institute of Polar Research, 10‐3 Midori‐cho, Tachikawa‐shi, Tokyo, 190‐8518 Japan²Department of Polar Science, the Graduate University for Advanced Studies, SOKENDAI, 10‐3 Midori‐cho, Tachikawa‐shi, Tokyo, 190‐8518 Japan
Published by arrangement with John Wiley & Sons

Identification and characterization of small extraterrestrial samples, such as small Antarctic meteorites <~1 cm, require the development of convenient laboratory‐based nondestructive analytical techniques using X‐ray diffraction (XRD). We explore the characterization criteria using an X‐ray diffractometer with a Gandolfi attachment using sub‐mm small fragments and powder aggregates for various kinds of stony meteorites and develop a new analytical technique. We primarily focus on olivine and pyroxene because they are the most abundant and important minerals for stony meteorite classification. A new calibration is performed to estimate the FeO content of the olivine in unequilibrated ordinary chondrites, which is useful for determining the meteorite chemical group irrespective of powder aggregate diameter but dependent on fragment grain diameter. This is because X‐ray intensity absorption is more effective for grains than for powders. Clinoenstatite (Cen) and orthoenstatite (Oen) were distinguished using the presence or absence of the isolated Oen 511 index peak. The method is also applied to other stony meteorites including carbonaceous chondrites and achondrites. The XRD results are consistent with studies based on polished sections involving textural observations by scanning microscope and chemical compositions of the constituent minerals. The new measurement technique presented here is convenient because of its use in air by the laboratory‐based X‐ray diffractometer, which makes it useful for the initial analyses of restricted extraterrestrial sample characterization.