| Abstract: | A new method of determining the age of native platinum based on alpha-radioactivity of one of its natural isotopes 190Pt is proposed. Due to a special form of occurrence of radiogenic helium in the crystal lattice of native metals as a helium cluster-bubbles, the stability of 190Pt-4He of the isotope system is extremely high in the natural environment. To check the efficiency of the proposed 190Pt-4He method of isotope geochronology, six independent mineral aggregates of native platinum from chromite-bearing dunites of the southern part of platinum-bearing zonal Galmoenan dunite-cllinopyroxenite-gabbro plutonic complex (Koryak-Kamchatka belt, Russia) were analyzed. The age calculated by the tangent of the 190Pt-4He isochrone slope angle equals 69.5 ± 4.9 mln years. The obtained age value coincides with the results of isotope datings, which were made previously by different methods of isotope geochronology. |
