Quantitative electronprobe microanalysis of rock-forming minerals

A number of well-characterized silicate minerals and metal oxides have been analysed by the electron-probe technique in two different instruments with a range of accelerating poten-tials. Simple oxides and minerals have been used as standards for the elements Na to Ca and pure metals for the elements Ti to Ni. Factors affecting the accuracy of analysis are discussed in detail. The effect of wavelength-shift errors is treated in a general manner and curves enabling the magnitude of the effect to be determined in any instrument are given. Corrections associated with X-ray generation (the atomic number correction), absorption and secondary excitation by characteristic and continuous radiation are examined separately. It is shown that analyses with an accuracy of 1 per cent or better can be obtained with recently developed correction methods and it is suggested that this approach is now a workable and possibly a preferable alternative to methods employing empirical calibration