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Przeobrażenia amfiboli w porfirach ryodacytowych z Zalasu koło Krakowa

Marszałek M., Czerny J.

Geologia / Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie

2009

T. 35, z. 2/1

159-166

The study was aimed at alteration of amphibole phenocrysts in the porphyries from Zalas. The alteration processes took place at the magmatic stage: development of orthopyroxenes and biotitization, and at the postmagmatic one: chloritization followed by argillitization and formation of feldspars, carbonate minerals, quartz, ilmenite, magnetite and hematite. Post-magmatic alteration resulted from hydrothermal processes of the metasomatic character.

On the palaeomagnetic age of the Zalas laccolith : (southern Poland)

Nawrocki J., Polechońska O., Lewandowska A., Werner T.

Acta Geologica Polonica

2005

Vol. 55, no. 3

229-236

An age estimation for the Zalas laccolith (Kraków area, South Poland) using the palaeomagnetic method is presented. 29 hand samples were taken from the rhyodacites and neighbouring Visean sediments cropping out in three localities. Two components of magnetization were isolated in the volcanic rocks and Visean sediments. The "A" component, common to the greenish rhyodacites and Visean sediments from Orlej, is carried by magnetite and is regarded as primary. Comparison of the mean inclination of this component with the expected (reference) stable European inclinations leads to the conclusion that the Zalas laccolith was emplaced about 280 Ma ago. The second component, "B", characteristic of the reddish rhyodacites, is carried by hematite and was recorded during the Late Permian (c. 260 Ma) metasomatic alterations of these rocks.The palaeomagnetic poles calculated for the "A" component show a distinct departure from the Permian segment of the Baltic apparent polar wander path (APWP) due to anticlockwise block rotations of the rocks studied that were most probably connected with the Early Permian sinistral transtensional tectonic regime in Central Europe.