DETERMINATION OF RARE-EARTH ELEMENTS IN SINGLE MINERAL GRAINS BY LASER ABLATION MICROPROBE INDUCTIVELY COUPLED PLASMA-MASS SPECTROMETRY - PRELIMINARY-STUDY

The application of a laser ablation microprobe with high spatial resol ution coupled with an inductively coupled plasma mass spectrometer to determine rare earth elements (REE) in single mineral grains is descri bed. The REE were determined down to sub-ppm concentrations using a 40 mum diameter ablation crater; quantification at the 100 ppm level usi ng a 4 mum diameter crater was demonstrated. A dual gas flow sample in troduction system was used to permit calibration of the ICP mass spect rometer with aqueous standards. Repeatability of the order of +/- 10% relative was achieved with the use of an internal standard when ablati ng a grain of clinopyroxene. Laser ablation craters with diameters of less than 5 mum were used to probe REE distributions within a grain of monazite. Comparison with data obtained by electron probe microanalys is (EPMA) showed that the detection limits using high resolution laser ablation ICP-MS were superior to those of EPMA for this application.