Abstract
Thorium, uranium, and potassium concentrations have been determined in nineteen sands and sandstones by γ-ray spectrometry, fluorometric uranium analysis, and α-counting. The samples were selected so that both common and extreme thorium and uranium ratios would be represented. The average and nearly uniform values found in orthoquartzitic, clay-free sands were potassium (as metal) 0.64 ± 0.04 per cent; thorium 1.7 ± 0.1 p. p. m.; and uranium 0.45 ± 0.05 p. p. m., giving a Th/U ratio of 3.8 ± 0.8. The Th/U ratio found is very near to that of average igneous rocks and may represent an independent determination of the average crustal Th/U ratio. Heavy mineral separations on some of the ordinary sands indicate that very little of the thorium, uranium, and potassium in a common sand is associated with the heavy detrital grains. Neglecting a very minor feldspar content, the radioactivity of the common sandstones studied is contained almost entirely in the quartz, where it appears to be largely related to microscopic and submicroscopic inclusions. The heavy detrital minerals do not begin to affect the Th/U ratio or concentration ratios until they occur in large quantities as in placer sands. Within experimental error, the modern beach sands studied were in radioactive equilibrium. These preliminary data provide some independent and experimental comparisons for the average thorium and uranium content of sandstones calculated from geochemical balances. The data are also helpful in constructing models of the changes in thorium and uranium ratios that might be observed in moving from a beach line through shallow water sediments to deep-water sediments.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call