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This paper describes sample processing and the results on X-ray fluorescence analysis of 10 major elements in silicate rocks by mounting sample glass-disks on the spectrometer. The sample disk was mad...e by fusing and molding in a Au-Pt crucible of a mixture of 1 g of rock powder, 5g of flux (Li_2B_4O_7 and about 30 mg of lithium bromide (LiBr・H_2O). Synthetic glasses prepared from pure chemical reagents yielded reliable and useful calibration curves for wide optimal ranges of composition. The use of the synthetic glasses for calibration eliminates errors which are usually associated with the geochemical standards. As a result, it is possible to estimate the matrix effects correctly. Detailed investigation of matrix effects on each spectrum was made possible to classify the measured elements into the following three groups, 1) elements with their Kα lines longer than the absorption edge of Si, whose Kα lines are absorbed mostly by oxygen, 2) elements with the absorption edges lying between Si-Kα and Cr-Kα, some of which are excited secondary by Si-Kα and the others are suppressed their Kα radiation by the absorption of Si, and 3) elements with the absorption edges shorter than Cr-Kα, whose Kα lines are absorbed by Fe. For the correction of the the matrix effects to the intensity of X-ray radiated from the measure element, it was found sufficient to consider only the element with the next largest mass absorption coefficient to get reliable analytical results. The effects of other elements are mostly negligible. It should be noticed that the Si-Kα line excites the associated Al to give additional Al-Kα radiation. Analytical results of geochemical inter-laboratory standards, which are very close to their recommended values, were listed in Table 4.続きを見る
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