Wiek izotopowy K/Ar granitoidów Kudowy

Abstract

Wykonano 8 oznaczeń wieku izotopowego K/Ar. Stwierdzono znaczny rozrzut wyników oznaczeń: od 311 do 365 MA. Wszystkie te oznaczenia wskazują jednak, że granit Kudowy jest starszy od fazy asturyjskiej i powstał prawdopodobnie w okresie górny dewon – wizen.

K/AR ISOTOPIC AGE OF KUDOWA GRANITOIDS

Granitoid Kudowa massif occurs in the complex of micaceous schists. The age of this massif has been the subject of controversies and the datings range from Asturlian to early Variscan and even Caledonian phases. Single K/Ar and Rb/Sr datings did not solve this problem.

Recently there were made 8 (Tab. 1, Fig. 2) K/Ar isotopic datings (with identification of Ar volume without isotopic control). The scattering of results obtained was large, from 311 to 365 m. y. but, nevertheless, they indicate that the Kudowa granitoid is older than the Asturian phase and presumably originated in the Late Devonian – Visean.

The scattering of the results obtained may be explained by either overprinting of ages related to two different orogenic phases, Bretonian and Sudetic, or the prolonged process of rheomorphic plasticization of granitoids in times of origin of the massif.

The datings showed that the Kudowa massif markedly differs in age from the Karkonosze, Strzegom and Strzelin massifs (Fig. 1), being similar to the Central Bohemian pluton and other granitoids from the interior of the Bohemian Massif.