THE USE OF ISOTOPE DILUTION IN DETERMINATION OF GEOLOGIC AGE OF MINERALS

Publisher Website
Google Scholar
Abstract
The mass spectrometer has been used for the estimation of trace quantities of rubidium and strontium. The isotope dilution technique developed by Aldrich has been extended so that 0.01% of rubidium and 0.0001% strontium have been analyzed with 100 mgm. of mineral. The use of small quantities for mass spectrometric determination allows the use of easily available fission strontium and rubidium. The radioactivity of the fission strontium also simplifies the chemical manipulation. No chemical separation from the mineral was required for the rubidium but the strontium was concentrated by ion exchange methods. Ages are presented for one lepidolite and two biotite minerals and their ages compared to those found by other methods. With one of the biotites the effect of weathering on the fractionation of rubidium from strontium has been studied.