^1,2,3Jing Yang,³Yangting Lin,^3,4,5Hitesh Changela,³Liewen Xie,⁶Bin Chen,³Jinhui Yang
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13559]
¹Department of Earth and Space Sciences, Southern University of Science and Technology, Shenzhen, 518055 China
²School of Earth and Space Sciences, University of Science and Technology of China, Hefei, 230026 China
³Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029 China
⁴Qianxuesen Laboratory of Space Technology, China Academy of Space Technology, Beijing, 100029 China
⁵Department of Earth & Planetary Sciences, University of New Mexico, Albuquerque, New Mexico, 87131 USA
⁶Department of Earth and Space Sciences, Southern University of Science and Technology, Shenzhen, 518055 China
Published by arrangement with John Wiley & Sons

The ungrouped achondrite Northwest Africa (NWA) 7325 parent body underwent a severe impact after primary crystallization, which completely melted plagioclase and partially melted pyroxene, followed by Mg diffusion into the adjacent plagioclase‐melt. The 26Al‐26Mg system was therefore modified, forming a pseudoisochron with an initial δ26Mg* of 0.094 ± 0.005‰ and an age of 4563.12 ± 0.33 Ma between the primary crystallization and subsequent impact event(s). The positive initial δ26Mg* can be interpreted by a model age of ~1.77 Ma after CAIs when a chondritic composition differentiated into a magma/rock with the Al/Mg ratio equivalent to that of NWA 7325 (~1.52). The LREE enrichments and a positive Eu anomaly suggest that the NWA 7325 parent magma formed by the melting of a plagioclase‐rich crustal lithology, which crystallized from a magma ocean. Differentiation of the magma ocean was prior to 1.77 Ma after CAIs. NWA 7325 is also unique by containing many rounded voids (5–6 vol%) interstitial to or enclosed in silicates, suggested to have formed by the leaching/vaporization of pre‐existing Fe‐Ca‐Mg‐Mn sulfides. This is supported by the similar morphology between voids and Cr‐bearing troilites, the discovery of relict oldhamite, and the highly reducing conditions of NWA 7325. The loss of pre‐existing sulfides could explain the unusual subchondritic Mn/Mg ratio of the bulk sample. Furthermore, the enrichment of moderately volatile elements (K/Th ratio ~2600–10,000) in the NWA 7325 parent body may result from the bonding with S2‐ in silicate melts under highly reducing conditions. NWA 7325 therefore provides evidence of sulfur‐rich magmatism in the early solar system.

¹Jean‐Pierre Lorand^2,3,4Jabrane Labidi,⁴Claire Rollion‐Bard,⁵Emilie Thomassot,⁶Jeremy J. Bellucci,⁷Martin Whitehouse,⁷Alexander Nemchin,⁸Munir Humayun,³James Farquhar,^9,10Roger H. Hewins,⁹Brigitte Zanda,⁹Sylvain Pont
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13564]
¹Laboratoire de Planétologie et Géodynamique à Nantes, CNRS, UMR 6112, Université de Nantes, 2 Rue de la Houssinère, BP 92208, 44322 Nantes Cédex 3, France
²Geophysical Laboratory, Carnegie Institution of Washington, Washington, District of Columbia, 20015 USA
³Department of Geology, University of Maryland, College Park, Maryland, 20740 USA
⁴Institut de physique du globe de Paris, CNRS, Université de Paris, F‐75005 Paris, France
⁵CRPG‐CNRS, Nancy, 54500 France
⁶Department of Applied Geology, Curtin University, Perth, Western Australia, 6845 Australia
⁷Laboratory for Isotope Geology, Swedish Mus. of Nat History, Stockholm, SE‐104 05 Sweden
⁸Department of Earth, Ocean & Atmospheric Science and National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida, 32310 USA
⁹Institut de Minéralogie, de Physique des Matériaux, et de Cosmochimie (IMPMC) ‐ Sorbonne, Université‐ Muséum National d’Histoire Naturelle, UPMC Université Paris 06, UMR CNRS 7590, IRD, UMR 206, 61 rue Buffon, 75005 Paris, France
¹⁰Department of Earth & Planetary Sciences, Rutgers University, Piscataway, New Jersey, 08854 USA
Published by arrangement with John Wiley & Sons

The sulfur isotope budget of Martian regolith breccia (NWA 7533) has been addressed from conventional fluorination bulk rock analyses and ion microprobe in situ analyses. The bulk rock analyses yield 865 ± 50 ppm S in agreement with LA‐ICP‐MS analyses. These new data support previous estimates of 80% S loss resulting from terrestrial weathering of NWA 7533 pyrite. Pyrite is by far the major S host. Apatite and Fe oxyhydroxides are negligible S carriers, as are the few tiny igneous pyrrhotite–pentlandite sulfide grains included in lithic clasts so far identified. A small nonzero Δ33S (−0.029 ± 0.010‰) signal is clearly resolved at the 2σ level in the bulk rock analyses, coupled with negative CDT‐normalized δ34S (−2.54 ± 0.10‰), and near‐zero Δ36S (0.002 ± 0.09‰). In situ analyses also yield negative Δ33S values (−0.05 to −0.30‰) with only a few positive Δ33S up to +0.38‰. The slight discrepancy compared to the bulk rock results is attributed to a possible sampling bias. The occurrence of mass‐independent fractionation (MIF) supports a model of NWA 7533 pyrite formation from surface sulfur that experienced photochemical reaction(s). The driving force that recycled crustal S in NWA 7533 lithologies—magmatic intrusions or impact‐induced heat—is presently unclear. However, in situ analyses also gave negative δ34S values (+1 to −5.8‰). Such negative values in the hydrothermal setting of NWA 7533 are reflective of hydrothermal sulfides precipitated from H2S/HS‐ aqueous fluid produced via open‐system thermochemical reduction of sulfates at high temperatures (>300 °C).

¹Ramakant R. Mahajan
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13565]
¹Physical Research Laboratory, Ahmedabad, Gujarat, 380009 India
Published by arrangement with John Wiley & Sons

Noble gases and nitrogen are investigated in eight individual chondrules of the Dhajala H3.8 chondrite. The mean cosmic ray exposure age of the chondrules using 21Ne and 38Ar is 5.9 ± 3.0 Ma. There is no significant evidence of a pre‐exposure for these chondrules. All the measured chondrules contain variable amounts of radiogenic 129Xe. Noble gas analysis indicates Q‐type gas incorporated in the chondrules. The chondrules have variable amounts of N2. The chondrules have distinct trapped N isotopic composition (δ15Nt varies from −24.1 ± 8.4‰ to 89.1 ± 12.7‰), which is inconsistent with Q‐gas and solar wind. These inconsistencies can be considered preliminary evidence in support of multiple trapped components in the chondrules. A heavy N signature component is observed in the chondrules studied contrasted with the solar wind composition. There is no correlation between the concentration of N2 and noble gases. Derivations of variable nitrogen observed in Dhajala (H3.8) chondrules reflect the gas captured at the time of formation, having heterogeneous isotopic signature in the nebula.