A new type of highly-vaporized microtektite from the Transantarctic Mountains

Abstract

We report on the discovery of microtektites (microscopic impact glass spherules) in a glacial moraine near Larkman Nunatak in the Transantarctic Mountains, Antarctica. The microtektites were identified based on their physical and chemical properties. Major and trace element compositions of the particles suggest that they may be related to the Australasian strewn field. This would further extend the current strewn field ~800 km southward. Depletion in volatiles and enrichment in refractory elements in Larkman Nunatak microtektites fit the volatilization trend defined by Australasian microtektites, suggesting that they may represent a new highly vapor fractionated member thereof. This observation is supported by their low vesicularity and absence of mineral inclusions. This discovery has strong implications for the formation of microtektites (i.e. their evolution with respect to the distance from the source crater). Finally, the discovery of potentially old (i.e. 0.8 Ma) microtektites in moraine has implications for the stability of the East Antarctic Ice Sheet in the Larkman Nunatak area over the last ~1 Ma and, as a consequence, the high efficiency of such moraines as traps for other extraterrestrial materials (e.g. micrometeorites and meteoritic ablation debris).