QUANTITATIVE-ANALYSIS OF MAJOR ELEMENTS IN SILICATE MINERALS AND GLASSES BY MICRO-PIXE

The Guelph micro-PIXE facility has been modified to accommodate a seco nd Si(Li) X-ray detector which records the spectrum due to light major elements (11 less than or equal to Z less than or equal to 20) with n o deleterious effects from scattered 3 MeV protons. Spectra have been recorded from 30 well-characterized materials, including a broad range of silicate minerals and both natural and synthetic glasses. Sodium i s mobile in some of the glasses, but not in the studied mineral lattic es. The mean value of the instrumental constant H for each of the elem ents Mg, Al, and Si in these materials is systematically 6-8% lower th an the H-value measured for the pure metals. Normalization factors are derived which permit the matrix corrections requisite for trace-eleme nt measurements in silicates to be based upon pure metal standards for Mg, Al and Si, supplemented by well-established, silicate mineral sta ndards for the elements Na, K and Ca. Rigorous comparisons of electron microprobe and micro-PIXE analyses for the entire, 30-sample suite de monstrate the ability of micro-PIXE to produce accurate analysis for t he light major elements in silicates. (C) 1997 Elsevier Science B.V.