A precise and rapid X-ray fluorescence technique has been devised for measuring concentrations of Ni, Cu, and Zn in the range from zero to 5,000 ppm in undiluted and unfused samples of powdered rock. The crux of the method is the use of primary WL^agr radiation coherently scattered and partly absorbed by the sample as a measure of the absorption characteristics of the sample for the X-ray wavelengths concerned. The method was calibrated by adding known amounts of Ni, Cu, and Zn to rock powders with a representative range of absorption characteristics, thereby establishing a family of linear calibration curves, each labeled with the associated intensity of the WL^agr line. Measurement of WL^agr line intensity could then be used to predict the slope of the calibration curve for any sample.

It was found that WL^agr line intensity could also be used to predict and correct for "instrumental contributions" of CuK^agr and NiK^agr line intensities, and to predict rather than measure background counting levels, thereby shortening analytical time appreciably.

The total time required for the determination of Ni, Cu, and Zn in one sample is about 15 minutes. The method has a precision (standard deviation of a single determination) of about ±4% for Zn, ±5% for Ni, and ±8% for Cu at a concentration level of 70 ppm. Determinations by this method (SRC) are compared with recommended values (USGS) for standard rocks W 1 and G 1 in the following table.

Table

The method has greatly accelerated studies of the distribution of traces of ore metals in Precambrian country-rock in Saskatchewan.

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