Determination of major and trace elements in rocks employing optical emission spectroscopy and X-ray fluorescence.

Abstract

An optical emission spectrometric method for major element determination and an X-ray fluorescence method for the determination of trace elements are described. The first method combines a tape machine with a direct reader and uses samples and synthetic standards which have been \"isoformed\" by dilution (1 to 12) with Li tetraborate containing Sr tetraborate and Co oxide and fusion. The major element results obtained by this nearly matrix independent method are used in the correction for matix effects in the trace element procedure where the samples and synthetic standards are diluted by mixing with Li tetraborate (2 to 1) before fusion. The synthetic standards are made from pure chemicals and pocessed in the same manner as the samples. Matrix effects are corrected for by means of absorption coefficients. Methods of correction based on the use of scattered background or incoherently scattered tube lines (Compton scatter) as intensity reference are also investigated and discussed. The major elements determined are Si, Al, Fe, Ti, Mg, Ca, Na, K, and Mn. At present the trace element programme includes Zr, Y, Sr, Rb, Zn, Cu, Ni, Cr, and Ba; the programme can easily be extended to include other elements. Results obtained for major and trace element abundances on some international reference samples and for trace elements in synthetic samples having major element composition quite different from that of the standards are presented.