Alexandre A. auteur aut IRD Basile Doelsch Isabelle auteur aut IRD Sonzogni C. auteur aut IRD Sylvestre F. auteur aut IRD Parron C. auteur aut IRD Meunier J.D. auteur aut IRD Colin Fabrice auteur aut IRD text journalArticle eng text/pdf born digital access The laser fluorination technique reported here for analyzing the oxygen isotope composition (delta O-18) of fine quartz size fractions 50-20, 20-10, 10-5, 5-2, 2-1 and < 1 mu m has been validated by comparison with the ion microprobe technique. It yields accurate 61 8 0 data with an external precision better than 0.15%.. This is a significant methodological improvement for isotopic studies dealing with materials such as soil or biogenic oxides and silicates: particles are often too small and recovered in insufficient amount to be easily handled for ion microprobe analysis. Both techniques were used to investigate delta O-18 composition of a Cretaceous quartzite and silcrete sequence from the South-East of France. Quartzite cements average 31.04 +/- 1.93%.. They formed from Mid-Cretaceous seawater. Higher in the series, silcretes cements average 26.66 +/- 1.36%. They formed from Upper- or post- Upper-Cretaceous soil water and groundwater. Oxygen isotope data show that the silicification steps from one mineralogical phase to another and from one layer to another (including from an upper pedogenic silcrete to a lower groundwater silcrete) occurred in a closed or weakly evaporating hydrological system. (c) 2006 Elsevier Inc. All rights reserved. specialized FRANCE 064 70 11 2827-2835 2006 0016-7037 https://www.documentation.ird.fr/hor/fdi:010035663 10.1016/j.gca.2006.03.003 0016-7037 [F B010035663] https://www.documentation.ird.fr/hor/fdi:010035663 https://www.documentation.ird.fr/intranet/publi/2006/06/010035663.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2006-08-10 2018-12-17 fdi:010035663 fre