¹Axel Wittmann,²Marc Biren
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14350]
¹Eyring Materials Center, Arizona State University, Tempe, Arizona, USA
²School of Earth and Space Exploration, Arizona State University, Tempe, Arizona, USA
Published by arrangement with John Wiley & Sons

Circa 300 years ago, a ~15-m iron asteroid impacted sand dunes in the Empty Quarter of Saudi Arabia, creating the Wabar craters and fragments of the IIIAB Wabar iron meteorite. A significant portion of the asteroid dissolved into the sand, forming a wide range of impactites including glassy Wabar pearls, dumbbells, and dark scoria-like material. In this study, we report the discovery of ~60–1400 nm nuggets of refractory highly siderophile elements (HSEs) dominated by Pt, Os, Ru, Ir, Re, and Rh in Wabar impact glass. These HSEs were distributed in the IIIAB iron at low parts per million and became concentrated up to ×44,000 in the nano-nuggets. The petrologic context of the nano-nuggets is consistent with the rapid dissolution of the iron meteorite into the dune sand target triggered by the impact shockwave, followed by the separation of immiscible HSEs from the silicate impact melt at 1900°C to over 2700°C. This research provides new insights into the formation processes of HSE nano-nuggets in impact glass and predicts the potential for similar findings at other impact sites.

²Larbi Zennouri,^1,2Hasnaa Chennaoui Aoudjehane,^3,4Luigi Folco,¹Taha Shisseh,⁵Abderrazak El Albani,⁵Arnaud Mazurier,¹Mohamed Hassan Leili
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14349]
¹GAIA Laboratory, Faculty of Sciences Ain Chock, Hassan II University of Casablanca, Casablanca, Morocco
²ATTARIK Foundation for Meteoritics and Planetary Science, Faculty of Sciences Ain Chock, Hassan II University of Casablanca, Casablanca, Morocco
³Dipartimento di Scienze della Terra, Università di Pisa, Pisa, Italy
⁴Centro per la Integrazione della Strumentazione della Università di Pisa, CISUP, Pisa, Italy
⁵Université de Poitiers, CNRS, IC2MP, Poitiers, France
Published by arrangement with John Wiley & Sons

Tamdakht meteorite is the most massive observed fall in Morocco with a total recovered mass of ~500 kg. Most of the specimens investigated in this study are covered by a well-developed primary fusion crust with thickness that reaches up to 12 mm. Macroscopic investigations reveal the development of complex fusion crust features indicative of unusual entry conditions. In some specimens, pieces of the primary fusion crust are missing, and the newly exposed areas developed a thinner fusion crust, which suggests that the former were removed during the late stages of the meteoroid’s flight. Meteorite fragments are enclosed in the primary fusion crust, implying a potential intershower debris transfer prior to the dark flight and that the broken pieces were retained by the viscous fusion crust. X-ray tomographic and backscattered electron imaging shows that the primary fusion is irregular in thickness and consists of three layers. The outer layer is mainly composed of magnetite that formed as a result of the reaction of atmospheric oxygen with Fe in the melt produced by heating. The middle layer consists of zoned olivine phenocrysts, large vesicles, and metal and sulfide grains. The innermost layer displays a lower degree of melting and contains tiny vesicles, as well as metal and iron sulfides in the form of blebs and veins invading the substrate. The textural, mineralogy, and the compositional variation of Tamdakht’s fusion crust imply a change in the degassing degree, temperature, and reaction with atmospheric oxygen from the surface inward.