Zmienione diabazy z okolicy Zawiercia

Wiesław Heflik, Marek Muszyński


Wykonano badania mikroskopowe, rentgenograficzne oraz chemiczne zmienionych diabazów, napotkanych wierceniem w okolicy Zawiercia. W profilu dajki wydzielono kilka stref o odmiennym stopniu i charakterze przeobrażeń skały diabazowej. Stwierdzono, że przeobrażenia te zostały spowodowane głównie przez procesy deuteryczne (uralityzacja, chlorytyzacja), hydrotermalne (feldspatyzacja, dolomityzacja) oraz wietrzenne (kaolinityzacja, kalcytyzacja). Zasugerowano decydujący wpływ przeobrażeń deuterycznych i hydrotermalnych na uformowanie się geochemicznych odmian diabazów rejonu zawierciańsko-mrzygłodzkiego.


Altered diabases encountered in A 4 borehole drilled in the vicinity of Zawiercie have been subjected to microscopic, X-ray, and chemical examination, results of which are presented in the paper. The rocks under consideration have been met between Silurian phyllites and metaclastics. at the depth from 161.9 to 214.1 m. It was possible to reveal that plagioclases and clinopyroxenes had been the main primary components participating in forming the initial structure of rocks in lower part of dike, while plagioclases and glass had governed the rock formation in upper part. Texture of the rocks had been intergranular and intersertal respectively, and their structure massive and orderless. The later alternations were . governed by deuteric, hydrothermal, and weathering processes which resulted in partial or complete (in some sections) modification of primary mineral composition and structure of rocks as well.

The deuteric processes in general were responsible for uralitization of piroxenes, chloritization of both the glass and the subsidiary amphiboles, and sericitization of plagioclases in part. A potassium metasomatism and a dolomitization were the main hydrothermal processes. The first one contributed to appearance of potassium feldspars side by side plagioclases, continuation of sericitization of plagioclases, and reconstruction of chlorites to hydromicas. Zones subjected to the dolomitization are marked out with decomposition of primary rock components and their discpiacement by dolomite: quartz (chalcedone), and hydromicas as well. A reservoir of acid or neutral magma was probably a source of hydrothermal fluids; this is evidenced by occurrence in the altered rocks of such trace elements as B, Li, Ga, Sb, Zn, Pb, Zr, and Ag.

Contrary to ideas of O. Juskowiak, H. Pendias. and W. Ryka (1978) the authors' opinion is that the deuteric and hydrothermal processes were of paramount importance in forming geochemical alterations of diabases within the Zawiercie - Mrzygłód area. Weathering in both the forms of kaolinization and calcitization of rock components concerned mainly the roof part of the dike.

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