Microtektites and glassy cosmic spherules from new sites in the Transantarctic Mountains, Antarctica

1Lauren E. Brase,1Ralph Harvey,2,3Luigi Folco,2Martin D. Suttle,4E. Carrie McIntosh,4James M. D. Day,5Catherine M. Corrigan
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13634]
1Department of Earth, Environmental, and Planetary Sciences, Case Western Reserve University, Cleveland, Ohio, 44106 USA
2Dipartimento di Scienze della Terra, Università di Pisa, Via S. Maria 53, 56126 Pisa, Italy
3CISUP, Centro per l’Integrazione della Strumentazione dell’Università di Pisa, Lungarno Pacinotti 43, 56126 Pisa, Italy
4Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, 92093 USA
5Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution, Washington, D.C., 20560 USA
Published by arrangement with John Wiley & Sons

We report on the geochemical analyses of glassy spherules from sediments at three Transantarctic Mountain locations and the discovery of Australasian microtektites at two of these sites. Australasian microtektites are present at Mt. Raymond (RY) in the Grosvenor Mountains and Meteorite Moraine (MM) at Walcott Névé, in the Beardmore Glacier region of Antarctica. The microtektites were identified based on their pale yellow appearance, the high concentrations of silica (SiO2 = 60 ± 7 wt%) and alumina (Al2O3 = 23 ± 4 wt%), and a K2O/Na2O > 1, which are all characteristics of microtektites and distinct from spherules of meteoritic origin. Additionally, trace element patterns for these microtektites match the upper continental crust compositions with enrichments in refractory elements and depletions in volatile elements, most likely as a result of melting and vaporization of source material. The presence of Australasian microtektites in RY sediment confirms the recent Australasian strewn field extension to Antarctica and the presence of highly volatile depleted microtektites. In addition to microtektites, thousands of chondritic spherules and a few unique differentiated cosmic spherules were identified in RY, MM, and Jacobs Nunatak sediments. Two unique spherules were calculated to have Fe/Mn ratios similar to micrometeorites assumed to be derived from Vesta (Fe/Mn 33.2 ± 0.5 atom%) and two other unique spherules are extremely rich in refractory components (Al2O3 ~ 30% and TiO2 = ~2%). The three sites examined are evidently successful cosmic dust and impact debris collectors, and thus are useful traps for recording and examining the nature of influx events.

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