Rare Earth Element analyses (SIMS)
When analyzing Rare Earth Elements in mineral samples, one has to deal with several molecular interferences of extremely close masses which cannot be separated using typical high mass resolution conditions.
To address such mass interference issues, energy filtering of the secondary ions with a well-controlled energy bandwidth is mandatory. The energy filtering technique is based on the fact that the energy distribution is narrower for polyatomic species compared to monoatomic species. By moving the energy slit off axis or by applying an offset to the sample voltage, it is possible to separate monoatomic from isobaric cluster ions.
For measuring trace elements content, a high-brightness oxygen source is also essential in order to obtain µm-scale elemental information with high sensitivity.
The IMS 7f-GEO has been designed to meet all these requirements
REE in Garnet grains
Analyses were performed using a 20nA O- primary beam (spot size 20µm) and the energy filtering technique. These results correspond to a mapping of REE concentration in a Garnet grain. One spot (over a total of 9) shows a significant enrichment for light REE compared the other areas.