Rb-Sr法による若干の黒雲母試料の年代測定

抄録

Age estmate for the biotite samples contained in six granitic rocks, three of which were from Kitakami massif and the other three were from Abukuma massif, was carried out by Rb-Sr method. After dissolving each biotite sample in 3N-HC1 solution, Rb and Sr were separated by an ion-exchange column. Quantitative analyses of Rb and Sr were carried out by isotope dilution method using ⁸⁷Rb- and ⁸⁶Sr-spikes, respectively.
Isotopic abundance ratio was mearsured using a modified Hitachi RMU-6 mass spectrometer with a triple-filament type surface ionization ion source. The initial ratio (⁸⁷Sr/⁸⁶Sr)₀ was obtained from the provisional isochron, and the ages for each three biotite samples of Kitakami and Abukuma massifs were estimated to be 121×10⁶ yr and 105×10⁶ yr, respectively.