Simultaneous in-situ multi-element analysis of minerals on thin section using LA-ICP-MS

In-situ trace-element analyses on minerals are especially useful for characterization of geological materials. We explored optimistic conditions of a inductively coupled plasma mass spectroscopy with laser-ablation sample introduction method (LA-ICP-MS) for in-situ quantitative trace-element analysis of geological materials on thin section. The sampling with an excimer laser with energy density of 8 J/cm² is appropriate for in-situ analysis of minerals on thin section based on ablation hole morphology. The rate of material removal is estimated from deep holes on a glass after 500 shots with energy on sample surface of 8 J/cm² to be approximately 0. 2ƒﾊm/pulse. 150-200 shots might be available for a sample prepared as normal thin section (30ƒﾊm in thickness). All data were obtained by ablating in He gas prior to combination with the dominant Ar carrier flow because ablation in He minimized post-ablation surface condensation, resulting in high sensitivity. We examined the relationship between the size of laser-ablation hole and sensitivity of analysis in conducting in-situ simultaneous quantitative LA-ICP-MS analysis of 37 elements including rare earth elements (REEs). The diameter of laser beam can be as small as 30ƒﾊm to obtain sufficiently good dataset for trace-element concentrations of minerals from thin section.