Wavelength-dispersive x-ray fluorescence spectrometric determination of Uranium, Thorium, Niobium, Zirconium, Yttrium, and Cerium in Syenitic Rocks

Syenitic rocks are potential sources of uranium, thorium, niobium, zirconium, yttrium, and cerium. Vast syenitic terrains in Peninsular and Extra-Peninsular India remain uncharacterised geochemically. Therefore, it is essential to delineate syenitic rocks anomalously enriched in these rare-elements.

The paper proposes a simple, accurate, precise, rapid, and non-destructive wavelength-dispersive x-ray fluorescence spectrometric technique for determining uranium, thorium, niobium, zirconium, yttrium, and cerium in syenitic rocks. The technique uses a sequential x-ray fluorescence spectrometer, 100 kV - 80 mA - 3 kW x-ray generator, rhodium x-ray tube, LiF 220 analysing crystal, fine (150 μm) collimator, air path, scintillation detector, short counting times, and the international syenite standards, SY-2 and SY-3, and secondary standards generated from them.

The accuracy of the technique is excellent (within 3% for thorium, niobium, and cerium) and very good (within 5% for uranium, zirconium, and yttrium). The precision is also excellent (within 2% for uranium, thorium, niobium, zirconium, and yttrium) and very good (within 7% for cerium). The lower limits of detection for the six elements are: uranium = 7 ppm; thorium = 6 ppm; niobium, zirconium, and yttrium = 2 ppm; and cerium = 44 ppm. The time taken for determining uranium, thorium, niobium, zirconium, yttrium, and cerium in a batch of twentyfour samples of syenitic rocks, for a replication of four analyses per sample, by one operator, using a manual wavelength-dispersive x-ray fluorescence spectrometer, is only twentyfour hours.