¹Miles Lindner,^1,2Dominik C. Hezel,^1,2Axel Gerdes,^1,2Horst R. Marschall,^1,3Frank E. Brenker
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.13917]
¹Institut für Geowissenschaften, Goethe-Universität Frankfurt, Altenhöferallee 1, 60438 Frankfurt am Main, Germany
²Frankfurt Isotope and Element Research Center (FIERCE), Goethe Universität, 60438 Frankfurt am Main, Germany
³Hawai‘i Institute of Geophysics and Planetology, University of Hawai‘i at Mānoa, Honolulu, Hawaii, 96822 USA
Published by arrangement with John Wiley & Sons

Enriched shergottites contain interstitial Si-rich mesostasis; however, it is unclear whether such mesostasis is formed by impact or magmatic processes. We use laser ablation multicollector inductively coupled plasma mass spectrometry U–Pb measurements of minerals within the interstitial Si-rich mesostasis and of merrillite within the coarse-grained groundmass of Martian-enriched gabbroic shergottite Northwest Africa (NWA) 6963. The date derived of tranquillityite, Cl-apatite, baddeleyite, and feldspar from the Si-rich mesostasis is 172.4 ± 6.1 Ma, and the derived merrillite date is 178.3 ± 10.6 Ma. We conclude, based on textural observation, that merrillite is a late magmatic phase in NWA 6963, that it was not produced by shock, and that its U–Pb-system was not reset by shock. The indistinguishable dates of the gabbroic merrillite and the minerals within the Si-rich mesostasis in NWA 6963 indicate that the Si-rich mesostasis represents a late-stage differentiated melt produced in the final phase of the magmatic history of the gabbroic rock and not a shock melt. This can likely be transferred to similar Si-rich mesostases in other enriched shergottites and opens the possibility for investigations of Si-rich mesostasis in enriched shergottites to access their magmatic evolution. Our results also provide a crystallization age of 174 ± 6 Ma (weighted average) for NWA 6963.

¹Deze Liu,¹Frédéric Moynier,^1,2Julien Siebert,^1,3Paolo A.Sossi,¹Yan Hu,¹Edith Kubik
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2022.09.043]
¹Université Paris Cité, Institut de Physique du Globe de Paris, 1 Rue Jussieu, 75005 Paris, France
²Institut Universitaire de France, Paris, France
³Institute of Geochemistry and Petrology, ETH Zürich, Sonneggstrasse 5, CH-8092 Zürich, Switzerland
Copyright Elsevier

In comparison with the Sun and CI chondrites, moderately volatile elements (MVEs) are depleted in terrestrial planets and other small, rocky differentiated bodies in the inner solar system. The abundances of most MVEs in the bulk silicate Earth (BSE) fall on a trend that defines a near log-linear decrease with their 50% nebular condensation temperature (). This temperature scale has traditionally been used to infer elemental volatility during planetary formation and accretion, however, indium (In) deviates from this correlation. Despite being a siderophile element that could have been depleted by core formation, In is overabundant for its calculated in the BSE, as well as in the silicate portions of other small bodies (e.g., Moon and Vesta). This overabundance of In indicates that , calculated under nebular conditions, may not be applicable to planetary evaporation that occurs at much higher oxygen fugacity (fO2) and pressure than nominal nebular conditions. Here, we conduct a series of evaporation experiments for basaltic melts to quantify the volatility of In under conditions relevant to planetary evaporation. Our results show that, when using the evaporation temperature , refers to the temperature at which 1% of element i has evaporated from liquid to gas phase under equilibrium) as the volatility scale, the abundances of volatile elements, including In, of the Moon and Vesta display a progressive depletion with increasing volatility (decreasing ). This smooth depletion pattern contrasts with the overabundance of In shown on the scale, suggesting that volatile depletion on small bodies occurred under non-nebular environment instead of during nebular condensation. On the other hand, the volatile element composition of the BSE (including In) could be explained by integrating i) early accreted precursor materials of the proto-Earth that underwent volatile loss under conditions more oxidizing than those of the solar nebula with ii) late added volatile-rich materials.