Glass spherules from Antarctica blue ice and deep-sea sediment of the Central Indian Ocean Basin

Abstract

We report the chemical composition of 176 glass spherules obtained from Antarctica blue ice and deep-sea sediments from the Central Indian Ocean Basin. This study compares the chemistry of glass spherules collected from various reservoirs, thereby allowing us to look into possible bias and efficiency of different collection techniques. Glass spherules have experienced extreme heating among the S-type cosmic spherules, and have suffered significant ablative elemental loss for which their precursors remain ambiguous. The previous model calculation for the glass spherules indicates chemical changes due to atmospheric entry. In addition, the earlier heating experiment results for the glass spherules show some insight into their formation processes. We report Ca-Al glass spherules that have high CaO+Al2O3 >9 wt% indicating larger particles with excessive evaporation of moderately volatiles (Fe, Si, Mg) resulting in refractory (Ca, Al) enriched glass or equilibration of minor Ca and Al phases in glass. Glass spherules from Antarctica and deep-sea are morphologically distinct and happen to have ablated most of their elemental Fe during atmospheric entry, however despite it, their bulk chemical composition and atomic ratios indicate to have a broad correspondence with carbonaceous chondrites, thereby, preserving the precursor properties.