Comparison of oxygen isotope data obtained by laser fluorination of olivine with KrF excimer laser and CO2 laser

The physics and chemistry of laser fluorination techniques that rely on CO2 lasers and excimer lasers differ on several fundamental levels: the mechan isms of laser-sample coupling, the time-scales of the interactions, and the nature of the fluorination chemistry. We examine the fluorination chemistr y of the mineral olivine (Mg, Fe)(2)SiO4) and use the results of our laser fluorination analyses to assess the accuracy and precision of both techniqu es. Oxygen isotope analyses of two populations of olivine grains made by us ing the CO2 laser fluorination technique give delta(18)O of 5.02 and 4.84 p arts per thousand, respectively. Analyses of the same sample populations by KrF excimer laser give delta(18)O of 5.07 and 5.00 parts per thousand, res pectively. We maintain that these two techniques an independent of one anot her and, therefore, that these results can be used to confirm their respect ive accuracy and precision. We have also examined the chemistry of the two techniques for fluorination of olivine with an eye toward pinpointing pitfa lls, advantages, and analytical strategies for each. Copyright (C) 1998 Els evier Science Ltd.