Oznaczenia wieku granitu Karkonoszy metodą izochronową, rubinowo-strontową. na podstawie całych próbek skalnych

Jean L. Duthou, Jean P. Couturie, Michał P. Mierzejewski, Christian Pin

Abstrakt


NEXT DATING OF GRANITE SAMPLE FROM THE KARKONOSZE MOUNTAINS USING RB-SR TOTAL ROCK ISOCHRONE METHOD

Summary
Different kind of Karkonosze granite were dated by four Rb/ Sr total rock isochrones. Furthermore, three other samples have been dated using the conventional method. The granite with biotite schlieren (Huta quarry, near Szklarska Poręba) gives the isochrone, which points out to the age of 328 M.y. and Sri = 0,7064 ± 22. The porphyritic granite from Michałowice quarry gives an isochrones age of 329 ± 17 M.y. with Sri = 0,7056 ± 11. The common isochrone, which contain the isotopic data from the lakuszyce borehole (porphyritic granite) and from the Michałowice quarry gives the age of 324 ± 11 M.y. with Sri = 0,7059 ± 7. The equigranular range granite, from the Mały Staw, yielded (five points isochrone) on 309 ± 3 M.y. with Sri = 0,7073. The leucogranite from the Huta quarry exhibits the age of 310 M.y. using conventional method. Two other samples, from Michałowice quarry, have been dated using the conventional method. These two samples are probably ancient enclaves, more or less assimilated by granitic magma. These samples exhibit the oldest age in the granitic Karkonosze Mts as yet, that is 350 M.y. The evolution of the Karkonosze pluton appears to have been rather a long process, which lasted at least over 20 M.y. It is suggested, that in Karkonosze Mts there exists some younger granite, which has not been dated till now.