Standard chemical-based tephra extraction methods significantly alter the geochemistry of volcanic glass shards

Claire L. Cooper*, Ivan P. Savov, Graeme T. Swindles

*Corresponding author for this work

    Research output: Contribution to journalArticle

    1 Citation (Scopus)

    Abstract

    The chemical compositions of tephra shards are widely utilised in a myriad of disciplines, including volcanology, petrology, tephrochronology, palaeoecology and climate studies. Previous research has raised concerns over the possible chemical alteration of microscopic (<100 µm) volcanic glass shards through standard extraction procedures, such as the widely used acid digestion method. This study subjects 10 samples of well-characterised volcanic glasses ranging from basalt to rhyolite to three common methods used in the extraction of volcanic material from lake sediments and peats. The major element geochemistry of each sample was analysed and compared with a control group. The results of this test indicate that basaltic and andesitic glasses are highly susceptible to chemical alteration, particularly to the concentrated corrosive materials used in acid and base digestion techniques. PERMANOVA analysis of the variation within groups suggests that the oxides most susceptible to variation are alkalis from groups I and II (K2O, Na2O, CaO, MgO) and SiO2, and the most stable oxides are Al2O3 and FeO. Felsic glasses are considerably less susceptible to alteration by both acidic (HCl, HNO3, H2SO4) and alkaline (KOH) digestions. Our findings have important implications for interpreting the geochemistry of volcanic glasses.

    Original languageEnglish
    Pages (from-to)697-707
    Number of pages11
    JournalJournal of Quaternary Science
    Volume34
    Issue number8
    DOIs
    Publication statusPublished - 28 Nov 2019

    Keywords

    • basaltic
    • EPMA
    • experimental methods
    • glass preservation
    • tephrochronology

    ASJC Scopus subject areas

    • Arts and Humanities (miscellaneous)
    • Earth and Planetary Sciences (miscellaneous)
    • Palaeontology

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