¹Z.E. Wilbur et al.(>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14086]
¹Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, USA
Published by arrangement with John Wiley & Sons

In 1972, Apollo 17 astronauts returned 170.4 kg of lunar material. Within 1 month of their return, a subset of those samples was specially curated with the forethought that future analytical techniques would offer new insight into the formation and evolution of the Moon. Of interest in this work is sample 71036, a basalt collected from the rim of Steno crater in the Taurus–Littrow Valley, which was stored frozen and was processed and released for study 50 years later. We report, for the first time, the detailed mineralogy and petrology of 71036 and its companion samples 71035, 71037, and 71055 using a novel combination of 2-D and 3-D methods. We investigate lunar volatiles through in situ measurements of apatite and 3-D measurements of vesicles to understand the degassing histories of the Steno crater basalts. Our coupled 2-D petrography and 3-D tomography data sets support a model of the Steno crater basalts crystallizing in the upper crust of a mare lava flow. Apatite F and OH chemistry and the late-stage deformation of voids and formation of smaller vesicles provide evidence supporting coeval degassing of volatiles and crystallization of mesostasis apatite in Apollo 17 basalts. This work helps to close knowledge gaps surrounding the origin, magmatic evolution, emplacement, and crystallization history of high-titanium basalts.

¹E.S. Steenstra,¹C.J. Renggli,¹J. Berndt,¹S. Klemme
Earth and Planetary Science Letters 622, 118406 Link to Article [https://doi.org/10.1016/j.epsl.2023.118406]
¹Institute of Mineralogy, University of Münster, Germany
Copyright Elsevier

Volatile element abundances in magmatic iron meteorites provide fundamental insights into the processing of volatile elements in the early solar system. Although Cu, Ge and Ag concentrations of magmatic iron meteorites deviate up to 4 orders of magnitude between different magmatic iron meteorite groups, the role of evaporation on these volatile abundances is poorly constrained. Here, we experimentally assess the volatility of Cu, Ge, Ag, S, Cr, Co, Ni, Mo, Ru, Pd, W, Re and Ir from metal and sulfide melts as a function of pressure (10−4 and 1 bar), temperature (1573–1823 K) and time (5–120 min) for two end-member compositions (Fe versus FeS). These novel experiments demonstrate that the presence of S is a major parameter in establishing the volatility of Cu, Ge, Mo, Ag, Ru, W, Re and Ir. At constant P-T and time, the volatility of Ge, Mo, Ru, W, Re and Ir is greatly increased in the presence of S, whereas Cu and Ag are less volatile in the presence of S. At 1773 K and ∼0.001 bar, the volatility of S is sufficiently high that the degassed FeS liquid showed immiscibility of a S-rich sulfide and a S-poor Fe melt. Empirical equations were derived that predict the evaporative loss of Cu, Ge, Mo, Ag from Fe and/or FeS liquid as a function of temperature and time. A comparison of the newly derived volatility sequences with commonly applied 50% condensation temperature models shows that the condensation temperature models cannot be applied to sulfur-bearing Fe liquids and therefore to magmatic iron meteorites. Application of the new models on previously derived elemental depletions in the IVB parent body shows that evaporation, if it occurred, cannot have taken place under S-rich conditions. The latter would result in a depletion of Mo, which is not observed for the IVB irons. However, evaporation of a S-free or S-poor Fe liquid reproduces the observed volatility depletion trend for IVB irons under a wider range of temperature and evaporation times, demonstrating the potential importance of evaporative loss on the IVB parent body.