Skład izotopowy i wiek bezwzględny ołowiu z galeny obszaru śląsko-krakowskiego

Abstract

ISOTOPIC COMPOSITION AND ABSOLUTE AGE OF GALENA LEAD FROM THE SILESIAN - CRACOW AREASummaryDeterminations of isotopic composition of 7 galena samples were made on the material from the Silesian-Cracow area, and 7 determinations made by various authors in various laboratories were collected. The samples come from the zinc-lead deposits occurring in the region under consideration, within the Lower Triassic and as small mineralization in the Devonian dolomites and Carboniferous diabases. Age determinations were made according to the ratio Pb206/Pb207. Except for one sample thought by the authors to be incorrectly identified, all the samples show insignificant variability of isotopic composition, approximate to the variability being a result of analytical error. This might prove a common genesis of the galena lead occurring in various stratigraphical horizons of the Silesian-Cracow area. Confidence interval for mean value amounts to from 76 mil. years to 147 mil. years, this corresponding with the whole time of both Cretaceous and Upper Jurassic. Within the same interval falls the mean from two datings (= 85 mil. years) made by the authors by means of K-A method on Carboniferous diabase samples. However, the authors are of the opinion that the results presented in the paper cannot be reckoned as an ultimate proof of the post-Triassic age of the mineralization in the Silesian-Cracow area. They think that a solution can be expected after helium dating that could be made on the selected pyrite samples.