Effects of the peat acid digestion protocol on geochemically and morphologically diverse tephra deposits. (11th July 2019)

• Record Type: Journal Article
• Authors: Monteath, Alistair J.; Teuten, Alex E.; Hughes, Paul D. M.; Wastegård, Stefan
• Is Part Of: Journal of quaternary science. Volume 34:Number 4/5(2019)
• Page Start: 269
• Page End: 274
• Publication Date: 2019-07-11
• Subjects: acid digestion -- chemical durability -- electron probe microanalysis -- peatlands -- tephra; Geology, Stratigraphic -- Quaternary -- Periodicals; Paleontology -- Quaternary -- Periodicals; 551.79
• DOI: 10.1002/jqs.3104
• Languages: English
• ISSNs: 0267-8179

Abstract

ABSTRACT: Tephra shards for electron probe microanalysis are most efficiently extracted from peat using acid digestion, which removes organic material that hinders density separation methods. However, strong acids are known to alter glass chemical compositions, and several studies have examined how acid digestion affects rhyolitic volcanic glass. The focus on rhyolitic tephra in these studies leaves considerable uncertainty, as the dissolution rates of natural glasses (including tephra) are determined by the chemical composition and surface area/volume ratio, both of which vary in tephra deposits. Here, we use duplicate samples of basaltic, trachydacitic and rhyolitic tephra to examine physical and geochemical alteration following acid digestion. Scanning electron microscope imagery reveals no discernible degradation of glass surfaces, and electron probe microanalysis results from duplicate samples are statistically indistinguishable. These findings suggest the acid digestion protocol for organic peats does not significantly alter glass geochemistry regardless of shard morphologies or geochemical compositions.