PROTON-MICROPROBE ANALYSES OF PLATINUM-GROUP ELEMENT AND GOLD GRAINS

Noble metal grains were separated from sediments of a paleoterrace of the Mekong river, northeast Thailand. Preliminary scanning-electron mi croscopy investigations show that all levels of the sediment are chara cterized by the coexistence of Au and Pt grains. This coexistence in o ne geological site is rare. Proton-microprobe analyses were carried ou t in order to detect trace elements which are indicative of their sour ce region(s) and the physico-chemical conditions during formation. Spe cial attention was given to the trace-element contamination of the use d absorbers and to the influence of the response function of our Si(Li )-detector on the data evaluation. Both effects play an important role in judging the reliability of our results. (C) 1997 Elsevier Science B.V.