DOUBLE β- DECAY OF 130TE: A NEW ISOTOPIC GEOCHRONOMERTER FOR GOLD MINERALIZTION

Abstract

The process of 2β- decay of 130Te with the formation of 130Xe was used for the tellurium-xenon isotopic dating of tellurium-bearing minerals accompanying gold mineralization. The correlation of 130Xe diffusion characteristics of tellurium minerals with the half-life of 130Te determined from the concentrations of 130Xe in these minerals suggests that the value of 2.7 × 1021 years proposed for the half-life of 130Te by some authors is probably overestimated because of the loss of part of radiogenic xenon during geologic history or younger ages of the tellurium minerals than was previously supposed. Minerals with the highest activation energy of 130Xe migration were used to calculate the half-life of 130Te. The most probable value is 0.75 × 1021 years. The ratio 130Xe/130Te was used to determine the ages of a number of tellurium minerals from gold deposits including Montezuma (Mexico), Boliden (Sweden), Kochbulak (Uzbekistan), and Aksu (North Kazakhstan). The values appeared to be much younger than the ages suggested for these deposits. This may be indicative of either later tellurium mineralization, easier recrystallization of tellurium minerals at superimposed processes, or very fast diffusion of radiogenic xenon in such minerals. To assess these effects and obtain reliable ages of tellurium minerals from isotopically open geochemical systems, we propose a neutron-induction variant of the tellurium-xenon method of isotopic geochronology.