¹Aleksandr A. Zubov,¹Tatyana G. Shumilova,¹Andrey V. Zhuravlev,¹Sergey I. Isaenko
American Mineralogist 106, 1860-1870 Link to Article [http://www.minsocam.org/msa/ammin/toc/2021/Abstracts/AM106P1860.pdf]
¹Institute of Geology of Komi Science Center of the Ural Branch of the Russian Academy of Sciences, Pervomayskaya st. 54, Syktyvkar, 167982, Russia
Copyright: The Mineralogical Society of America

X‑ray computed microtomography (CT) of impact rock varieties from the Kara astrobleme is used to test the method’s ability to identify the morphology and distribution of the rock components. Three types of suevitic breccias, clast‑poor melt rock, and a melt clast from a suevite were studied with a spatial resolution of 24 μm to assess CT data values of 3D structure and components of the impactites.
The purpose is first to reconstruct pore space, morphology, and distribution of all distinguishable
crystallized melt, clastic components, and carbon products of impact metamorphism, including the impact glasses, after‑coal diamonds, and other carbon phases. Second, the data are applied to analyze
the morphology and distribution of aluminosilicate and sulfide components in the melt and suevitic
breccias. The technical limitations of the CT measurements applied to the Kara impactites are discussed. Because of the similar chemical composition of the aluminosilicate matrix, glasses, and some lithic and crystal clasts, these components are hard to distinguish in tomograms. The carbonaceous matter has absorption characteristics close to air, so the pores and carbonaceous inclusions appear similar.
However, X‑ray microtomography could be used to prove the differences between the studied types
of suevites from the Kara astrobleme using structural‑textural features of the whole rock, porosity,
and the distributions of carbonates and sulfides.

^1,2Laurence A.J. Garvie,³Chi Ma,²Soumya Ray,⁴Kenneth Domanik,⁵Axel Wittmann,²Meenakshi Wadhwa
American Mineralogist 106, 1828-1834 Link to Article [http://www.minsocam.org/msa/ammin/toc/2021/Abstracts/AM106P1828.pdf]
¹Center for Meteorite Studies, Arizona State University, 781 East Terrace Road, Tempe, Arizona 85287-6004, U.S.A.
²School of Earth and Space Exploration, Arizona State University, 781 East Terrace Road, Tempe, Arizona 85287-6004, U.S.A.
³Division of Geological and Planetary Sciences, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, U.S.A.
⁴Lunar and Planetary Laboratory, University of Arizona, 1415 N 6th Avenue, Tucson, Arizona 85705, U.S.A.5Eyring Materials Center, Arizona State University, Tempe, Arizona 85287, U.S.A.
Copyright: The Mineralogical Society of America

Carletonmooreite (IMA 2018-68), Ni3Si, is a new nickel silicide mineral that occurs in metal nodules from the Norton County aubrite meteorite. These nodules are dominated by low-Ni iron (kamacite), with accessory schreibersite, nickelphosphide, perryite, and minor daubréelite, tetratae-nite, taenite, and graphite. The chemical composition of the holotype carletonmooreite determined by wavelength-dispersive electron-microprobe analysis is (wt%) Ni 82.8 ± 0.4, Fe 4.92 ± 0.09, and Si 13.08 ± 0.08 (n = 6, total = 100.81) giving an empirical formula of (Ni2.87Fe0.18)Σ3.05Si0.95, with an end-member formula of Ni3Si. Further grains discovered in the specimen after the new mineral submission extend the composition, i.e., (wt%) Ni 81.44 ± 0.82, Fe 5.92 ± 0.93, Cu 0.13 ± 0.02, and Si 13.01 ± 0.1 (n = 11, total = 100.51 ± 0.41), giving an empirical formula (Ni2.83Fe0.22Cu0.004)Σ3.05Si0.95. The backscat-
tered electron-diffraction patterns were indexed by the Pm3m auricupride (AuCu3)-type structure and
give a best fit to synthetic Ni3Si, with a = 3.51(1) Å, V = 43.2(4) Å3, Z = 1, and calculated density of
7.89 g/cm3. Carletonmooreite is silver colored with an orange tinge, isotropic, with a metallic luster and occurs as euhedral to subhedral crystals 1 × 5 μm to 5 × 14 μm growing on tetrataenite into kamacite. The dominant silicide in the Norton County aubrite metal nodules is perryite (Ni,Fe)8(Si,P)3, with
carletonmooreite restricted to localized growth on rare plessite fields. The isolated nature of small euhedral carletonmooreite single crystals suggests low-temperature growth via solid-state diffusion
from the surrounding kamacite and epitaxial growth on the tetrataenite. This new mineral is named in honor of Carleton B. Moore, chemist and geologist, and founding director of the Center for Meteorite Studies at Arizona State University, for his many contributions to cosmochemistry and meteoritics.