High precision δ17O isotope measurements of oxygen from silicates and other oxides: method and applications
✍ Scribed by M. F. Miller; I. A. Franchi; A. S. Sexton; C. T. Pillinger
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 112 KB
- Volume
- 13
- Category
- Article
- ISSN
- 0951-4198
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✦ Synopsis
The use of infrared laser-assisted fluorination to release oxygen from milligram quantities of silicates or other oxide mineral grains is a well-established technique. However, relatively few studies have reported the optimisation of this procedure for oxygen-17 isotope measurements. We describe here details of an analytical system using infrared (10 mm) laser-assisted fluorination, in conjunction with a dual inlet mass spectrometer of high resolving power ($250) to provide 17 O and 18 O oxygen isotope measurements from 0.5-2 mg of silicates or other oxide mineral grains. Respective precisions (1') of typically 0.08 and 0.04% are obtained for the complete analytical procedure. Departures from the mass-dependent oxygen isotope fractionation line are quantified by D 17 O; our precision (1') of such measurements on individual samples is shown to be AE0.024%. In turn, this permits the offset between parallel, mass-dependent fractionation lines to be characterised to substantially greater precision than has been possible hitherto. Application of this system to investigate the 17 O versus 18 O relationship for numerous terrestrial whole-rock and mineral samples, of diverse geological origins and age, indicates that the complete data set may be described by a single, mass-dependent fractionation line of slope 0.5244AE 0.00038 (standard error).