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

M Van Ginneken,M.J Genge,R.P Harvey

doi:10.1016/j.gca.2018.02.041

M Van Ginneken, M.J Genge + Show 1 more

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https://doi.org/10.1016/j.gca.2018.02.041

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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 end-member thereof. This observation is supported by their low vesicularity and absence of mineral inclusions. This discovery has significant 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).

Highlights

Introduction1994; Artemieva, 2008; Glass and Simonson, 2013)
Microtektites are the microscopic counterpart of tektites, which are glass objects resulting from the melting and vaporization of the Earth’s crust during hypervelocity impacts of extraterrestrial bodies (Glass, 1990; Koeberl,⇑ Corresponding author at: IARC, Department of Earth Science and Engineering, Imperial College London, Exhibition Road, London SW7 2AZ, UK.1994; Artemieva, 2008; Glass and Simonson, 2013)
The surface of most particles is smooth and featureless (Fig. 3a), but 8% of the particles show weathering pits (Fig. 3b) identical to those observed on the surfaces of V-type cosmic spherules extracted from the same glacial moraine (Van Ginneken et al, 2016)

Summary

Introduction

1994; Artemieva, 2008; Glass and Simonson, 2013) They are usually scattered over regions distal to impact craters called strewn fields (e.g., Glass and Simonson, 2013). Four major strewn fields have been discovered on the Earth’s surface (i.e. Australasian, Central European, Ivory Coast and North America; Glass and Simonson, 2013).

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