Uwagi o wieku bezwzględnym skał – nowe kierunki interpretacji w geochronologii izotopowej

Jan Burchart

Abstract


REMARKS ON ABSOLUTE AGE OF ROCKS: MODERN TRENDS IN ISOTOPE GEOCHRONOLOGY

Summary

The paper presents modern approaches in interpretation of results of isotopic dating. Problem arising from argon loss during geological processes and its bearing on the “ages” obtained by means of Ar/K methods is discussed. Also the cases of excess argon and possible influence of alkali exchange are reviewed. A special attention is paid to Compston-Jeffery model of strontium evolution and to the concept of isochrons. As an example the author's determinations of the crystalline rocks from the Tatra Mts. (Central Carpathians) made in Graduate Research Center of the Southwest, Dallas, Texas, are reported: Mineral isochrons of two gneisses give the ages of 300 and 313 m.y., and 87Sr/86Sr initial ratios of 0.714 and 0.717 respectively, while a total rock isochron yields 415 m.y. and initial ratio of 0.706.


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