Highly siderophile element nano-nuggets in Wabar impact glass

Abstract

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.