de MARIA LEMNE, ELEONORA VIJDEA, ANCA TANASESCU,
OLIVIA ROMANESCU, AUREL RADULESCU
Institutul de Geologie si Geofizica, Bucuresti
DETERMINATION OF THE ABSOLUTE AGE BY MEANS OF THE A – K
ISOTOPIC DILUTION VARIANT
(Abstract)
The A–K isotopic dilution method has been tested for the young period
determinations. Argon enriched in Ar38 isotope (Ar38 – 98,34%; Ar40 =
94%; Ar36 = 0,72%) has been used as a dilution factor.
The radiogenic Ar40 extraction has been carried out in a reactor plant and
in a purification installation constituted of a titanium furnace and an electric
titanium tube. The isotopic ratio determinations are effectuated with MS – 20
spectrometer.
The sensitivity and accuracy of the radiogenic Ar40 analysis and of the absolute
age determinations have been controlled with three international standards:
biotite LP – 6; muscovite 4 – M and phonollite M – Z. These
standard cover a large time interval from 125 to 7.1 million years, with the
following errors: 4.5%, 3.5% and 25%.
The I.G.G. laboratories can determine with accuracy ages lower than the Upper
Miocene.