OXYGEN-ISOTOPE ANALYSIS OF QUARTZ BY NEODYMIUM-YTTRIUM ALUMINUM GARNET LASER-FLUORINATION

Oxygen isotope measurements of powdered quartz samples have been perfo rmed following liberation of oxygen by a fluorination reaction induced by heating the sample with radiation from a neodymium-yttrium alumini um garnet laser (wavelength 1064 nm). The fluorination reagent used wa s chlorine trifluoride. In order to effect absorption of the laser ene rgy by the sample, nickel powder was mixed with the quartz. Sodium chl oride was also mixed with the sample, which is important in reducing t he incidence of problematic species generated during fluorination.; Th e amount of sample analysed was normally less than 1 mg. Analytical pa rameters such as the choice of chemicals for flux, flux-to-sample rati o, amount of nickel powder, pressure of chlorine trifluoride and power of the laser were examined in detail using a quartz standard. Sodium chloride has proved to be a better flux than potassium chloride, not s howing any strong dependence of delta(18)O with any of the parameters and producing oxygen yields ranging from 70 to 90% of the expected val ue. Although the delta(18)O values obtained by this technique, with 1 mg samples, were lighter than expected by about 0.8 parts per thousand , the precision was good (0.1 parts per thousand), enabling a correcti on to be applied to the measured value.