Oxygen isotope analyses of fine-grained minerals and rocks using the laser-extraction technique

The δ18O values of fine-grained materials made with the laser-extraction technique are often lower than those obtained conventionally. We propose a simple method to overcome this problem that involves the mixing of samples with a LiF binder and pressing the powder into pellets prior to evacuation and analysis. The presence of the LiF allows for rapid fluorination of all minerals or whole-rock samples to be made, thus eliminating potential problems related to loss of partially reacted ejecta, slow laser heating, and incidental fluorination. Accurate isotope determinations of fine-grained materials can be made with this method.