ABSTRACT

Four volcanic glass samples on the INternational focus group on Tephrochronology And Volcanism (INTAV) sample mount described by Kuehn et al. (2011) were analyzed to establish a new methodology for measurement of major and trace elements in Quaternary tephras by femtosecond laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). NIST SRM 610 and 612 glasses were used for calibration of the measurement of 58 elements from Li to U in two rhyolitic glass samples (Lipari obsidian ID3506 and Old Crow tephra) and the phonolitic Sheep Track tephra. In addition to the NIST SRM glasses, USGS BCR-2G and BHVO-2G basaltic glasses were measured for calibration of the major elements (i.e., Na, Mg, Al, Si, K, Ca, Ti, Mn, and Fe) in the basaltic Laki tephra. Most major element data for the four volcanic glass samples, and those for ZrO₂ in Lipari obsidian and Sheep Track tephra deviate <10% from the preferred values obtained by electron-beam analysis techniques complied in Kuehn et al. (2011). P₂O₅ values range from 74% to 110% of the preferred values in Kuehn et al. (2011), and are consistent within uncertainties. BaO values are 7–24% of the preferred values of Kuehn et al. (2011), but are similar to those obtained using other trace element analytical techniques, such as X-ray fluorescence and ICP atomic emission spectroscopy. Our trace element data are generally consistent with those obtained in previous studies. However, heterogeneously distributed microcrysts in the glass materials may affect some elements such as B, P, and Cr. The analytical data for the INTAV samples obtained using femtosecond LA-ICP-MS and the NIST SRM and USGS standard glasses demonstrate that this approach is a viable alternative to electron-beam microanalysis techniques for the determination of major elements in rhyolitic and basaltic glasses.