40Ar-39 Ar ages of selected rocks and minerals from the Kraków-Lubliniec Fault Zone, and their relation to the Paleozoic structural evolution of the Malopolska and Brunovistulian terranes (S Poland)

Abstract

New ⁴⁰Ar-³⁹ Ar isotope ages of mafic and felsic rocks from the contact zone of the Malopolska and Brunovistulian terranes are presented and discussed. A ⁴⁰Ar-³⁹ Ar age estimation of detrital muscovite from a Lower Devonian "old red" type sandstone drilled on the Malopolska side of this zone was also done. Our studies reveal that three events of Paleozoic magmatic activity took place in the study area. The oldest, late Emsian episode is recorded by a diorite from the core part of an intrusion penetrated by the Sosnowiec IG 1 borehole. A younger, Visean event is documented by a diabase cored in the borehole WB-137. Diabases from Niedwiedzia Góra and from borehole PZ-10, and a rhyodacite from borehole 16-WB gave early Permian (Artinskian-early Sakmarian) ages. The youngest, middle Sakmarian age was obtained for a diabase forming the external parts of the Sosnowiec IG 1 polycyclic intrusion. A diorite penetrated by the Sosnowiec IG 1 borehole was emplaced during the late Emsian extension that preceded the Lochkovian-Pragian? transpression related to the final docking and amalgamation of the Brunovistulian Terrane.