Die Isotop-Röntgenfluoreszenz Analyse und ihre Anwendung bei geochemischen Untersuchungen in Grönland

The principles of X-ray fluorescence ar e briefly described. In particular, two methods of radioisotope X-ray fluorescence analysis ar e discussed: (a) radioisotope X-ray fluorescence analysis by means of portable apparatus incorporating scintillation or proportional counters and balanced differential X-ray filters, and (b) radioisotope X-ray fluorescence spectrometry by means of Si(Li) or Ge(Li) semiconductor detectors. For a portable radioisotope X-ray fluorescence analyser calibration curves were established for Cr, Ni.Cu.Zn, Zr,
Nb, Mo, La+Ce, and Pb in rock powders, Ti.Zr, and Nb in plane cut rock surfaces, and Zr, Nb, and La+Ce in rock outcrops. Detection limits found from calibration data were 0.3% Cr, 0.06% Ni, 0.14%Cu, 0.14%Zn, 0.04% Zr 0.07% Nb, 0.03% Mo, 0.02% La+Ce and 0.1 % Pb in rock powders, 0.07% Ti, 0.4% Zr and 0.1% Nb in cut rock surfaces, and 0.14% Zr, 0,15% Nb and 0.16% La+Ce in rock outcrops. Values for the accuracy and the precision of these analyses ar e given. Special investigations include the dependence of the analytical result on the grain size of the sample material and experiments regarding the critical sample weight. Si(Li) and Ge(Li) X-ray spectrometers for the analysis of rock samples are described. Two methods of X-ray spectrum reduction carried out by means of a 32K computer were investigated: simple channel-by-channel integration and least-squares fitting. Calibration data on rock powders yielded for the Si(Li) X-ray spectrometer (lmCi Cd for excitation of characteristic X-rays) 23 ppm Rb, 110 ppm Sr, 69 ppm Zr, 206 ppm Nb, and 172 ppm Mo as detection limits for the analysis of rock powders. For plane cut rock surfaces and the Ge(Li) X-ray
pectrometer (10 mCi Am for excitation purpose) detection limits of 400 ppm Ce and 180 ppm Nd were obtained. The influence of interferences on the analytical result such as overlapping of X-ray peaks, absorption of X-rays in the sample and grain-size effects are dealt with. Special emphasis is given to the correction of X-ray intensities by means of scattered X-radiation. Portable radioisotope X-ray fluorescence analysers were applied in geochemical investigations of Zr, Nb, and La+Ce in a series of alkaline rocks of the IUmaussaq intrusion. South Greenland, of Ho in molybdenitebearing rocks, and of Zr and La+Ce in sedimentary rocks from East Greenland. Semiconductor X-ray spectrometers were used in the analysis of sediments from a stream draining the Hinaussaq intrusion. South Greenland, in the analysis of La, Ce, Ni, Cu, and Zn in stream sediments from East Greenland, and in investigations of Rb, Sr, Zr, Mb, Sn, Ba, La, Ce, Fr, and Nd in cut drill cores.