¹Kelsey B. Prissel,¹Michael J. Krawczynski,²Nicole X. Nie,²Nicolas Dauphas,
²Sarah M. Aarons,²Andy W. Heard,³Michael Y. Hu,³E. Ercan Alp,³Jiyong Zhao
Geochimica et Cosmochimica Acta (in Press) Open Access Link to Article [https://doi.org/10.1016/j.gca.2024.01.006]
¹Department of Earth and Planetary Sciences, Washington University in St. Louis, 1 Brookings Drive, St. Louis, 63123, MO, USA
²Origins Laboratory, Department of Geophysical Sciences and Enrico Fermi Institute, The University of Chicago, 5734 South Ellis Avenue, Chicago, 60637, IL, USA
³Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, 60439, IL, USA
Copyright Elsevier

Basaltic volcanism on the Moon produced low- and high-Ti mare basalt suites that are also distinct with respect to their iron, titanium, and magnesium isotopic compositions. Here, the equilibrium fractionation of Fe and Ti isotopes between ilmenite and melt was experimentally investigated in order to evaluate the role of ilmenite in generating the isotopic compositional variability among the lunar mare basalts. Ilmenite crystallization experiments were conducted using two bulk compositions: an ilmenite-saturated basaltic andesite and an ilmenite-saturated Apollo 14 black glass, and the Fe and Ti isotopic compositions of the experimental ilmenites and glass (quenched melt) were analyzed using solution MC-ICPMS after hand-picking. Additionally, Nuclear Resonant Inelastic X-ray Scattering (NRIXS) measurements on synthetic ilmenite were conducted and compared to previous NRIXS measurements on synthetic lunar glasses in order to derive temperature-dependent equilibrium ilmenite-melt Fe isotopic fractionations. Experimentally determined ilmenite-melt fractionations were then incorporated into a lunar magma ocean crystallization model that tracks the major element and isotopic compositional evolution of lunar magma ocean cumulates and residual liquid. There is good agreement between the Fe equilibrium isotopic fractionation measured by NRIXS and the laboratory equilibration experiments, and we find that the isotopic fractionation is sensitive to ilmenite compositional differences (0 vs. 10% Fe³⁺). Further, the light Ti isotopic composition of ilmenite relative to the melt (Δ49Ti‰=ilmenite-melt−0.09±0.03‰ at 1100 ^∘C) is consistent with the higher coordination of Ti in ilmenite relative to melts and results of previous studies. The modeled Ti isotopic compositions for lunar magma ocean cumulates display Ti isotopic variability sufficient to explain the low- and high-Ti mare basalt sources. However, the difference in Fe isotopic composition between the low- and high-Ti mare basalts cannot be attributed solely to ilmenite fractionation. Instead, Fe isotopic fractionation by additional products of lunar magma ocean crystallization, such as clinopyroxene, is required to generate the inferred Fe and Mg isotopic variability in the lunar mantle. Alternatively, the Fe and Mg isotopic compositions of the lunar mare basalts may indicate Fe-Mg interdiffusion has occurred in the Ti-rich component of the mare basalt source regions via reaction between ilmenite cumulates and the olivine- and pyroxene-rich lunar mantle.

^1,2Hasnaa Chennaoui Aoudjehane
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14126]
¹GAIA Laboratory, Faculty of Sciences Ain Chock, Hassan II University of Casablanca, Casablanca, Morocco
²ATTARIK Foundation for Meteoritics and Planetary Science, Casablanca, Morocco
Published by arrangement with John Wiley & Sons

Morocco is known for the high number of meteorites collected in its territory, including finds and falls. This is explained by the large size of the Moroccan Sahara, the guarantee of security in this desert, and the large community of well-trained Moroccan hunters and nomads who roam through it. Despite this richness, most meteorites collected in Morocco are sold abroad and exported. The exportation of meteorites as well as other geoheritage samples such as fossils and minerals was not completely legal or illegal as there was no dedicated regulation. Since 2000, the APPGM (Association pour la Protection du Patrimoine Géologique du Maroc) a Non-Governmental Organization (NGO) dedicated to the preservation of the Moroccan geoheritage began working with the Moroccan Geological Survey, on a draft of a specific law dedicated to geoheritage. It was fundamental to benefit from the experience of other countries with a high number of meteorites where exportation is not allowed and that are losing their meteorites to illegal exportation. The author recommended a win-win regulation that would allow the legal collection and exportation of meteorites under clear rules benefiting both hunters and scientists but also the country. In 2014, Morocco updated its law regarding mines. One article cited geoheritage as including fossils, minerals, and meteorites and mentioned that their collection and exportation would be regulated by decree. In 2019, the Moroccan Geological Survey and APPGM prepared the application decree of this article that has been discussed and approved by the Moroccan government and implemented in February 2020. This situation is unique in the region as well as compared to the other countries with a high potential of meteorites collection. Meteorite researchers and collectors all over the world should be aware of this regulation in Morocco to make their acquisitions legal. They should request a copy of the “End of the work” from local traders, the receipt from the Geological survey, and the certificate of export from customs. It is an important ethical and scientific responsibility of our community.