Inter-laboratory comparison of oxygen isotope compositions from biogenic silica

Bernhard Chapligin (1) , Melanie J Leng (2) , Elizabeth Webb (3) , Anne Alexandre (4) , Justin P Dodd (5) , Akira Ijiri (6) , Andreas Lücke (7) , Aldo Shemesh (8) , Andrea Abelmann (1) , Ulrike Herzschuh (1) , Fred J Longstaffe (3) , Hanno Meyer (1) , Robert Moschen (7) , Yusuke Okazaki (6) , Nicholas H Rees (9) , Zachary D Sharp (5) , Hilary J Sloane (2) , Corinne Sonzogni (4) , George E.A. Swann (10) , Florence Sylvestre (4) , Jonathan J Tyler (9) , Ruth Yam (8)

1 AWI - Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung = Alfred Wegener Institute for Polar and Marine Research = Institut Alfred-Wegener pour la recherche polaire et marine
2 NERC Isotope Geosciences Laboratory
3 UWO - University of Western Ontario
4 CEREGE - Centre européen de recherche et d'enseignement des géosciences de l'environnement
5 The University of New Mexico [Albuquerque]
6 JAMSTEC - Japan Agency for Marine-Earth Science and Technology
7 IBG - Institute of Bio- and Geosciences [Jülich]
8 Department of Earth and Planetary Sciences [Rehovot]
9 University of Oxford
10 UON - University of Nottingham, UK

Several techniques have been introduced in the last decades for the dehydration and release of O2 from biogenic silica (opal-A) for oxygen-isotope analysis. However, only one silica standard is universally available: a quartz standard (NBS28) distributed by the IAEA, Vienna. Hence, there is a need for biogenic silica working standards. This paper compares the existing methods of oxygen-isotope analyses of opal-A and aims to characterize additional possible working standards to calibrate the δ18O values of biogenic silica. For this purpose, an inter-laboratory comparison was organized. Six potential working standard materials were analysed repeatedly against NBS28 by eight participating laboratories using their specific analytical methods. The materials cover a wide range of δ18O values (+23 to +43‰) and include diatoms (marine, lacustrine), phytoliths and synthetically-produced hydrous silica. To characterize the proposed standards, chemical analyses and imaging by scanning electron microscopy (SEM) were also performed. Despite procedural differences at each laboratory, all methods are in reasonable agreement with a standard deviation (SD) for δ18O values between 0.3‰ and 0.9‰ (1σ). Based on the results, we propose four additional biogenic silica working standards (PS1772-8: 42.8‰; BFC: 29.0‰; MSG60: 37.0‰; G95-25-CL leaves: 36.6‰) for δ18O analyses, available on request through the relevant laboratories.

Domaines: Géochimie; Sciences de l'environnement

Bernhard Chapligin, Melanie J Leng, Elizabeth Webb, Anne Alexandre, Justin P Dodd, et al.. Inter-laboratory comparison of oxygen isotope compositions from biogenic silica. Geochimica et Cosmochimica Acta, 2011, 75 (22), pp.7242 - 7256. ⟨10.1016/j.gca.2011.08.011⟩. ⟨hal-01909561⟩