The laser microprobe and its application to the study of C and O isotopes in calcite and aragonite
Abstract
Laser probe microsampling of C and O from carbonate minerals for isotopic analysis was achieved by focussing a Nd : YAG high-power laser through microscope optics onto a sample situated in a vacuum chamber. The laser beam, about 10 μm in diameter, was used to ablate an area on the sample (a slab or a thin section), liberating CO 2 gas. The CO 2 was purified and led directly into a mass spectrometer for isotopic analysis. Fractionation effects and reproducibility were assessed by analyzing homogenized natural and synthetic carbonate standards that had been well characterized using conventional acid digestion techniques. The data indicated that δ13C was not significantly fractionated during laser ablation. However, the δ18O of the evolved CO 2 was 1.7ℵ lighter than O in the original CaCO 3 in the case of calcite, 2.5ℵ lighter for aragonite. This fractionation was not dependent on laser operating conditions, although the operating conditions were important for efficient CO 2 production. Optimal reproducibility in carbonates was in the order of ± 0.2ℵ (σ) for both δ13O.
- Publication:
-
Sedimentary Geology
- Pub Date:
- December 1989
- DOI:
- 10.1016/0037-0738(89)90023-7
- Bibcode:
- 1989SedG...65..211S