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Combined oxygen and silicon isotope analysis of biogenic silica

Leng, Melanie; Sloane, Hilary. 2008 Combined oxygen and silicon isotope analysis of biogenic silica. Journal of Quaternary Science, 23 (4). 313-319. 10.1002/jqs.1177

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Abstract/Summary

There is increasing interest in the use of biogenic silica O and Si isotope ratios to understand climate and environmental processes. Virtually all of the fairly substantial body of literature deals with either oxygen or silicon. This is partly because measurement of oxygen isotope composition is done using either vacuum dehydration, isotope exchange or stepped fluorination techniques, while increasingly researchers are turning to multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) for Si isotope analysis, even though Si isotope analysis can be done using fluorination methods used for the oxygen isotope measurements. Here we describe a procedure for simultaneous determination of isotopic abundances of oxygen and silicon from the same aliquot of biogenic silica. Pure silica is dissociated into O and Si compounds using a fluorination technique, in which reaction with bromine pentafluoride (BrF5) produces oxygen (O2, subsequently converted to CO2), silicon tetrafluoride (SiF4) and other fluorine by-products (e.g. BrF3). These compounds are cryogenically separated using cold traps. Yields for oxygen and silicon recovery are 70–80% for biogenic silica depending on the nature of the hydrous layer and 97–99% for pure quartz. Reproducibility of the oxygen isotopic composition is ca. 0.3% and silicon between 0.06–0.12%.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1002/jqs.1177
Programmes: BGS Programmes 2008 > NERC Isotope Geoscience Laboratory
ISSN: 0267-8179
Additional Keywords: Oxygen isotopes, Silicon
NORA Subject Terms: Earth Sciences
Date made live: 04 Jul 2008 13:46
URI: http://nora.nerc.ac.uk/id/eprint/3558

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