Obsidian and mafic volcanic glasses from the Philippines and Vietnam found in the Paris Museum Australasian tektite collection

Abstract

During the systematic magnetic susceptibility survey of the Paris Museum Australasian tektite collection, we identified three previously overlooked occurrences of volcanic glass that resembles tektites, based on anomalous magnetic properties, high water content, the presence of microcrystals, and anomalous chemical composition. These occurrences are from the Phu Yen province in south‐central Vietnam (two rhyolitic glass fragments) and from the Philippines: one from northern Luzon Island (a basaltic rounded etched glass), one from Santa Mesa near Manilla (a dozen small rounded rhyolitic gravels). The two occurrences in the Philippines are quite similar to previously described volcanic glasses from the nearby Pagudpod and Nagcarlan localities, respectively. The rhyolitic glass specimens from the Phu Yen province are the first documentation of a geological occurrence of obsidian in Vietnam. This work is a warning note that glass samples with anomalous properties found among tektite collections may correspond to volcanic pseudotektites instead of real tektites with anomalous composition. The basaltic glass sample from the Philippines locally shows microcrystalline quench textures previously unknown in natural samples. These findings may also be of interest for archeologists involved in glass artifacts sourcing.

Magnetic Properties of Australasian Tektites From South China

“…Rock magnetism is an important method to identify natural glasses of different origins (Rochette et al, 2022), and it has been extensively used to investigate the thermal history, source materials, and parent crater of various impact glasses, especially tektites. For example, Senftle et al (2000) distinguished Belize tektites from those of the other four major Cenozoic strewn fields based on the much higher magnetic susceptibilities of belizites (average 121 × 10 −9 m 3 /kg), which are closer to those of the other impact glasses formed by the Pantasma crater (Rochette et al, 2019).…”

“…Rock magnetism is an important method to identify natural glasses of different origins (Rochette et al., 2022), and it has been extensively used to investigate the thermal history, source materials, and parent crater of various impact glasses, especially tektites. For example, Senftle et al.…”