¹Robert M. Hazen,¹Shaunna M. Morrison
American Mineralogist 106, 1388–1419 Link to Article [http://www.minsocam.org/msa/ammin/toc/2021/Abstracts/AM106P1388.pdf]
¹Earth and Planets Laboratory, Carnegie Institution for Science, 5251 Broad Branch Road NW, Washington, D.C. 20015, U.S.A
Copyright: The Mineralogical Society of America

Part V of the evolutionary system of mineralogy explores phases produced by aqueous alteration,
metasomatism, and/or thermal metamorphism—relicts of ancient processes that affected virtually all
asteroids and that are preserved in the secondary mineralogy of meteorites. We catalog 166 historical
natural kinds of minerals that formed by alteration in the parent bodies of chondritic and non-chondritic
meteorites within the first 20 Ma of the solar system. Secondary processes saw a dramatic increase in
the chemical and structural diversity of minerals. These phases incorporate 41 different mineral-forming
elements, including the earliest known appearances of species with essential Co, Ge, As, Nb, Ag, Sn, Te,
Au, Hg, Pb, and Bi. Among the varied secondary meteorite minerals are the earliest known examples
of halides, arsenides, tellurides, sulfates, carbonates, hydroxides, and a wide range of phyllosilicates.
Keywords: Philosophy of mineralogy, classification, mineral evolution, natural kinds, meteorite

¹M.Matsuoka,²T.Nakamura,³N.Miyajima,⁴T.Hiroi,⁵N.Imae,⁵A.Yamaguchi
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2021.08.042]
¹ISAS/JAXA, Sagamihara, Kanagawa 252-5210, Japan
²Tohoku University, Sendai, Miyagi 980-8578, Japan
³Bayerisches Geoinstitut, University of Bayreuth, Bayreuth 95440, Germany
⁴Brown University, Providence, RI 02912, USA
⁵Research National Institute of Polar Research, Tachikawa, Tokyo 190-8518, Japan
Copyight Elsevier

Spectral and mineralogical analyses were performed using nine naturally hydrated and dehydrated carbonaceous chondrite samples which were classified into heating stages (HS) from I to IV based on previous X-ray diffraction results. In-situ heating of samples at 120–400 °C was performed during spectral measurements and successfully removed absorbed water and part of rehydrated water from chondrite samples. Reflectance spectra of HS-I samples show the positive slope in visible (Vis)-infrared (IR) range and the significant 0.7- and 3-μm absorption bands. The 0.7-μm band appears in only HS-I sample spectra. With increasing temperature of heating, (1) Vis-IR slope decreases, (2) the 3-μm band becomes shallower, and (3) Christiansen feature (CF) and Reststrahlen bands (RB) shift toward longer wavelength. TEM-EDX analyses showed that the matrix of strongly-heated chondrites consists of tiny olivine, low-Ca pyroxene, and FeNi metallic particles mostly smaller than 100 nm in diameter, instead of Fe-rich serpentines and tochilinite observed in the HS-I chondrite. Therefore, in proportion to the heating degree, amorphization and dehydration of serpentine and tochilinite from HS-I to HS-II may cause the 0.7- and 3-μm band weakening, spectral bluing and darkening of chondrite spectra. In addition, formation of secondary anhydrous silicates and FeNi-rich metal grains at HS-IV would be responsible for the 3-μm band depth decrease, spectral reddening and brightening, CF peak shift, and RB changes of chondrite spectra. Those spectral changes in response to mineralogical alteration processes will be useful to interpret planetary surface composition by remote-sensing observations using ground-based or airborne/space telescopes or spacecraft missions.

^1,2Denis Fougerouse,^1,3Aaron J.Cavosie,^1,4Timmons Erickson,^1,2Steven M.Reddy,^1,3Morgan A.Cox,²David Saxey,²William Rickard,⁵Michael T.D.Wingate
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2021.08.025]
¹School of Earth and Planetary Sciences, Curtin University, Perth, Australia
²Geoscience Atom Probe Facility, John de Laeter Centre, Curtin University, Perth, Australia
³Space Science and Technology Centre, Curtin University, Perth, Australia
⁴Jacobs – JETS, Astromaterials Research and Exploration Science division, NASA Johnson Space Center, Houston, USA
⁵Geological Survey of Western Australia, Department of Mines, Industry Regulation and Safety, Perth, Australia
Copyright Elsevier

To test the potential of deformation twins to record the age of impact events, micrometre-scale size mechanical twins in shocked monazite grains from three impact structures were analyzed by atom probe tomography (APT). Shocked monazite from Vredefort (South Africa; ∼300 km crater diameter), Araguainha (Brazil; ∼40 km diameter), and Woodleigh (Australia; 60 to 120 km diameter) were studied, all from rocks which experienced pressures of ∼30 GPa or higher, but each with a different post-impact thermal history. The Vredefort sample is a thermally recrystallised foliated felsic gneiss and the Araguainha sample is an impact melt-bearing bedrock. Both Vredefort and Araguainha samples record temperatures > 900 °C, whereas the Woodleigh sample is a paragneiss that experienced lower temperature conditions (350 – 500 °C). A combined 208Pb/232Th age for common {1} twins and shock-specific (01) twins in Vredefort monazite was defined at 1979 ± 150 Ma, consistent with the accepted impact age of ∼2020 Ma. Irrational η1 [0] shock-specific twins in Araguainha monazite yielded a 260 ± 48 Ma age, also consistent with the accepted 250-260 Ma impact age. However, the age of a common (001) twin in Araguainha monazite is 510 ± 87 Ma, the pre-impact age of igneous crystallisation. These results are explained by the occurrence of common (001) twins in tectonic deformation settings, in contrast to the (01) and irrational η1 [0] twins, which have only been documented in shock-deformed rocks. In Woodleigh monazite, APT age data for all monazite twins [(001), (01), newly identified 102°/<23> twin], and host monazite are within uncertainty at 1048 ± 91 Ma, which is interpreted as a pre-impact age of regional metamorphism. We therefore are able to further constrain the poorly known age of the Woodleigh impact to < 1048 ± 91 Ma. These results provide evidence that Pb is expelled from monazite during shock twin formation at high temperature (Vredefort and Araguainha), and also that Pb is not mobilised during twinning at lower temperature (Woodleigh). Our study suggests that twins formed during shock metamorphism have the potential to record the age of the impact event in target rocks that are sufficiently heated during the cratering process.

¹Masashi Shidare,^bRyoichi Nakada,^3,4Tomohiro Usui,¹Minato Tobita,²Kenji Shimizu,⁵Yoshio Takahashi,¹Tetsuya Yokoyama
Geochimica et Cosmochinica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2021.08.026]
¹Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, Tokyo 152-8551, Japan
²Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 200 Monobe, Nankoku, Kochi 783-8501, Japan
³Earth-Life Science Institute, Tokyo Institute of Technology, 2-12-1 Ookayama, Tokyo 152-8551, Japan
⁴Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA), 3-1-1 Yoshinodai, Sagamihara, Kanagawa 252-5210, Japan
⁵Department of Earth and Planetary Science, the University of Tokyo, 7-3-1 Hongo, Tokyo 113-8654, Japan
Copyright Elsevier

The surface of Mars has experienced progressive oxidation, resulting in the formation of sulfate minerals as evidenced from surface exploration missions. However, no clear evidence for the presence of sulfate minerals has been reported within Martian meteorites. This study examined sulfur speciation in impact glasses of three basaltic shergottites, Elephant Moraine (EETA) 79001, Larkman Nunatak (LAR) 06319, and Dhofar 019, using X-ray absorption near-edge structure (XANES) spectroscopy. The measured XANES spectra were classified into four types: (1) sulfide, (2) highly reduced sulfide glass (∼IW+1), (3) mixture of sulfide and sulfate, and (4) sulfate. The sulfate spectra observed from EETA79001 and LAR 06319 were mixed with sulfide from the reduced igneous host rock as impact glasses were formed by shock on the surface of Mars, both sulfide and sulfate would have possibly originated on Mars. Besides, highly reduced sulfide present in the same impact glasses is inconsistent with secondary alteration on the oxic Earth’s environment. In contrast to EETA79001 and LAR 06319, all of the XANES spectra from Dhofar 019 showed the only sulfate, whose origin is most likely from terrestrial alteration. Combining with the geochemical signatures of volatile elements (e.g., D/H, C, and halogens) in impact glasses of EETA79001 and LAR 06319, we propose two possible scenarios for the formation of sulfate species to the shergottite host-rocks: (i) oxidation of sulfide minerals by subsurface oxic water in Mars, or (ii) precipitation of sulfate mineral derived from Martian subsurface water. The difference between the two models is the source of S(VI) species, whether it originated from (i) magmatic sulfide in shergottite or (ii) sulfate ion in the subsurface water/ice. Both models indicate that the ancient (∼4 Ga) water reservoir might have already been oxic, and it requires post-magmatic water–rock interaction that formed sulfate minerals whose oxidized signatures were incorporated into impact glass.