DETERMINATION OF TRACE-ELEMENTS IN SILICATE ROCKS BY X-RAY-FLUORESCENCE SPECTROMETRY ON 1 5-GLASS DISCS - COMPARISON OF ACCURACY AND PRECISION WITH PRESSED POWDER PELLET ANALYSIS/

A fusion procedure commonly used for major element analysis of silicat e rocks (1:5 sample to flux ratio, using 0.7 g of sample) was used to determine a small group of trace elements (Cu, Zn, Rb, Sr, Y, Zr, Nb) by X-ray fluorescence. Compton scatter peak ratioing was successfully used for matrix corrections, despite the thickness of the glass discs being only 1.7 mm. Precision and detection limits were compared with p ressed pellet values. For most elements, routine analytical precision is better with powder pellets and detection limits are worse in glass discs, by an average factor of 2, considering all elements analyzed. A ccuracy was evaluated with international reference materials and for m ost of the determinations, good or excellent agreement with recommende d values was obtained. The main advantages of using glass discs for th e trace element determination are the possibility of analyzing small a mounts of sample and the suppression of any mineralogical effects in t he glass discs, which can also be used to determine major elements.