¹Borovička, J.,¹Spurný, P.,¹Shrbený, L.
Astronomical Journal 160, 42 Link to Article [DOI: 10.3847/1538-3881/ab9608]
¹Astronomical Institute of the Czech Academy of Sciences, Fričova 298, CZ-25165 Ondrejov, Czech Republic

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¹Busarev, V.V.,²Badyukov, D.D.,³Pronina, N.V.
Geochemistry International 58, 795-801 Link to Article [DOI: 10.1134/S0016702920070058]
¹Moscow State University (MSU), Sternberg State Astronomical Institute, Moscow, 119992, Russian Federation
²Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences (GEOKHI RAS), ul. Kosygina 19, Moscow, 119991, Russian Federation
³Moscow State University, Geological Faculty, Moscow, 119991, Russian Federation

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^1,2Luca Bindi,³Vladimir E. Dmitrienko,⁴Paul J. Steinhardt
American Mineralogist 105, 1121-1125 Link to Article [http://www.minsocam.org/MSA/AmMin/TOC/2020/Abstracts/AM105P1121.pdf]
¹Dipartimento di Scienze della Terra, Università degli Studi di Firenze, Via La Pira 4, I-50121 Firenze, Italy
²CNR-Istituto di Geoscienze e Georisorse, Sezione di Firenze, Via La Pira 4, I-50121 Firenze, Italy
³A.V. Shubnikov Institute of Crystallography, FSRC “Crystallography and Photonics” RAS, 119333 Moscow, Russia
⁴Department of Physics, Princeton University, Jadwin Hall, Princeton, New Jersey 08544, U.S.A
Copyright: The Mineralogical Society of America

Until 2009, the only known quasicrystals were synthetic, formed in the laboratory under highly controlled conditions. Conceivably, the only quasicrystals in the Milky Way, perhaps even in the Universe, were the ones fabricated by humans, or so it seemed. Then came the report that a quasicrystal with icosahedral symmetry had been discovered inside a rock recovered from a remote stream in far eastern Russia, and later that the rock proved to be an extraterrestrial, a piece of a rare CV3 carbonaceous chondrite meteorite (known as Khatyrka) that formed 4.5 billion years ago in the pre-solar nebula. At present, the only known examples of natural quasicrystals are from the Khatyrka meteorite. Does that mean that quasicrystals must be extremely rare in the Universe? In this speculative essay, we present several reasons why the answer might be no. In fact, quasicrystals may prove to be among the most ubiquitous minerals found in the Universe.

¹Francis M. McCubbin,²Jessica J. Barnes
The American Mineralogist 105, 1270-1274 Link to Article [http://www.minsocam.org/MSA/AmMin/TOC/2020/Abstracts/AM105P1270.pdf]
¹NASA Johnson Space Center, Mailcode XI, 2101 NASA Parkway, Houston, Texas 77058, U.S.A.
²Lunar and Planetary Laboratory, University of Arizona, 1629 E University Blouvard, Tucson, Arizona 85721, U.S.A
Copyright: The Mineralogical Society of America

We conducted in situ Cl isotopic measurements of apatite within intercumulus regions and within a holocrystalline olivine-hosted melt inclusion in magnesian-suite troctolite 76535 from Apollo 17. These data were collected to place constraints on the Cl-isotopic composition of the last liquid to crystallize from the lunar magma ocean (i.e., urKREEP, named after its enrichments in incompatible lithophile trace elements like potassium, rare earth elements, and phosphorus). The apatite in the olivine-hosted melt inclusion and within the intercumulus regions of the sample yielded Cl-isotopic compositions of 28.3 ± 0.9‰ (2σ) and 30.3 ± 1.1‰ (2σ), respectively. The concordance of these values from both textural regimes we analyzed indicates that the Cl-isotopic composition of apatites in 76535 likely represents the Cl-isotopic composition of the KREEP-rich magnesian-suite magmas. Based on the age of 76535, these results imply that the KREEP reservoir attained a Cl-isotopic composition of 28–30‰ by at least 4.31 Ga, consistent
with the onset of Cl-isotopic fractionation at the time of lunar magma ocean crystallization or shortly thereafter. Moreover, lunar samples that yield Cl-isotopic compositions higher than the value for KREEP are likely affected by secondary processes such as impacts and/or magmatic degassing. The presence of KREEP-rich olivine-hosted melt inclusions within one of the most pristine and ancient KREEP-rich rocks
from the Moon provides a new opportunity to characterize the geochemistry of KREEP. In particular, a broader analysis of stable isotopic compositions of highly and moderately volatile elements could provide an unprecedented advancement in our characterization of the geochemical composition of the KREEP reservoir and of volatile-depletion processes during magma ocean crystallization, more broadly.