Geochemical characterization of scoriaceous and unmelted micrometeorites from the Sør Rondane Mountains, East Antarctica: Links to chondritic parent bodies and the effects of alteration

• DOI: 10.1016/j.gca.2023.06.002
• Publication Date: 2023-06-10T12:51:00Z
• Authors: Flore Van Maldeghem; Matthias van Ginn...; Bastien Soens; Felix Kaufmann; Seppe Lampe; Lisa Krämer Ruggiu; Lutz Hecht; Philippe Claeys; Steven Goderis
• Keywords: 13. Climate action; 01 natural sciences; 0105 earth and related environmental sciences

Micrometeorites originate from the interplanetary dust complex and continuously fall to Earth's surface in large amounts. About 10 20% of micrometeorites are not melted upon reaching surface, preserving primary features characteristics parent material. Consequently, unmelted micrometeorites, together with scoriaceous an intermediate form between cosmic spherules pivotal documenting nature evolution as well modifications experienced by during atmospheric entry. Based on their petrographic features, here we identified characterized 64 diameters varying 90 410 μm fine-grained sediment sampled Sør Rondane Mountains East Antarctica. size distribution, show a clear distinction (<300 μm) (>400 imply accumulation mechanism or exposure history distinct other collections (e.g., Transantarctic Mountains). Different windows, weathering processes environmental factors snow cover) could affect composition preserved particles. A selection particles (n = 49) was further for geochemical high-precision oxygen isotope ratios identify potential bodies document alteration histories. 63% particles, exhibiting both coarse- textures, derive carbonaceous chondritic precursors. Two (∼4%) display anomalously 16O-poor isotopic compositions similar that previously observed (giant) classified "group 4" These thought unidentified body located specific region protoplanetary disk may have been history, recent studies linking them CY chondrites. Only single particle (∼2%) can be assigned ordinary parentage confidence. The partially hydrated matrix suggests this might consistent Semarkona-like body. Approximately 10% studied exhibit extensive evidence secondary terrestrial formation (hydr)oxides residence Antarctic environment, preventing detailed identification. Ten (∼20%) group due ambiguous values. Overall, statistics study agree those reported different fraction. Clear associations textural groups established. Even though generally considered pristine often do any obvious weathering, chemical data obtained confirm occur at microscale subaerial should evaluated caution.