MICROBEAM AMS - PROSPECTS OF NEW GEOLOGICAL APPLICATIONS

AMS applications in geology have hitherto concentrated on the use of c osmogenic isotopes and rare in-situ produced isotopes for geomorpholog ical and geophysical studies. Special features of AMS lend themselves to more general applications to other isotopes and geochronological sy stems. In-situ measurements in geochronology carried out with ion-micr oprobes are restricted by isobaric and molecular mass interferences to special systems where the problem is minimal. AMS can be used to alle viate this mass interference problem, and opens up the prospect of a l ess restrictive in-situ microanalysis for geochronology. At CSIRO, a m icrobeam AMS system designed to achieve this capability is under const ruction. With this system, several interesting applications such as th e Re-Os system became accessible more conveniently. The U-Pb system be comes accessible for hydrous minerals, and Rb-Sr systems for Rb-rich s amples. In addition, microbeam AMS allows determination of trace eleme nts at lower levels than those accessible with the proton microprobe. This paper discusses these prospects and describes the AUSTRALIS syste m (AMS for Ultra Sensitive TRAce element and Isotopic Studies) being d eveloped at CSIRO.