Boron-bearing microcrysts in volcanic glass shards

Abstract

B concentrations of three of four representative volcanic glass samples (Sheep Track, Laki, and Old Crow tephras) obtained by 193 nm excimer LA differ from those obtained by 260 nm femtosecond LA, apart from the Lipari obsidian. The rarity of microcrysts in the Lipari obsidian, and the different ablation depths of the two types of LA analyses, suggest that microcrysts affected the B concentrations. XRD analysis of the Sheep Track and Laki tephras identified peaks of B-bearing minerals. The Old Crow tephra showed no significant XRD peaks, but may contain B-bearing nanolites.