Exploring meteorite collections via non-destructive micro X‑ray fluorescence analysis

Meteorites offer a unique view on the formation and evolution of our solar system. Thousands of such samples exist in meteorite collections all over the world; however, this resource is by far not fully explored. One reason, among others, is that some rare meteorites , particularly those of historic importance, are usually museum objects. The sampling of such material should be avoided or significantly reduced, for example, by using non-destructive analytical tools. For this, spatially resolved X-ray fluorescence (micro-XRF) is an ideal technique. Several micro-XRF instruments that are currently available allow studying samples in the size range of meters to sub-millimeters with high spatial resolutions in the low µm range. There are several major advantages in micro-XRF with respect to other conventional micro-analytical instruments (e.g., SEM) including (1) the capability to handle large samples; (2) low detection limits (usually below those of SEM EDX systems), and (3) high analysis speed allowing to cover large areas in relative short time. We explore the analytical capacity of two different micro-XRF instruments. The first is an open beam system (M6 JETSTREAM) and the second (M4 TORNADO Plus) is an instrument with a vacuum chamber and several options for improving the light-element sensitivity. Here, we present several case studies from chondrites and achondrites with sample sizes up to 16 × 20 cm. We evaluate quantification of chemical compositions (whole rock, fragments and mineral components) by standard-free and standard-based methods and discuss possible micro-XRF-based classification of meteorites based on established criteria.