IMAGING ELEMENT-DISTRIBUTION PATTERNS IN MINERALS BY LASER ABLATION - INDUCTIVELY COUPLED PLASMA - MASS SPECTROMETRY (LA-ICP-MS)

We demonstrate the application potential of laser-ablation - inductively coupled plasma - mass spectrometry (LA-ICP-MS) to map the distribution of major and trace elements in a variety of samples. The examples cover a wide range of elements, including the rare-earth elements (REE) and platinum-group elements (PGE). In order to test the capabilities of the technique, samples of different matrices were analyzed (i.e., carbonates, silicates and sulfides). The main obstacle to rapid processing of element-distribution maps by laser ablation was data processing. This has been overcome with the development of new software, such as IOLITE, and improved designs of the laser-ablation cells and refinements of commercially available laser systems. It is possible to obtain fully quantified concentration maps for single-matrix samples using parallel adjoining line-scans. Single spot-analyses will result in better precision and accuracy, but the geochemical images are superior to conventional laser-ablation spot-analysis because they reveal geochemical details that are not visible under the microscope and cannot be appreciated with single spot-analyses. In addition to providing spatial information, the individual line-scans that are used in the image acquisition offer the option to obtain quantitative results along any part of the scan. Using LA-ICP-MS imaging, our dataset reveals zoned REE distribution in garnet crystals, a heterogeneous occurrence of the PGE in sulfides, as well as the internal chemical structures in ooids with respect to conditions of growth.