Zagadnienie genezy skały skaleniowej ze Strzeblowa koło Sobótki

Abstract

PROBLEM OF ORIGIN OF FELDSPAR ROCKS FROM STRZEBLÓW, NEAR SOBÓTKASummaryThe feldspar rocks from Strzeblów occur within the north-eastern margin of the Strzegomz-Sobótka granite massif. The results of the recent mineralogic-petrographical studies demonstrate that these rocks reveal a visible structural and mineral-chemical variation. Seemingly, the rocks look like a slightly weathered granite that underwent beaching. A closer study shows, however, that is not an intermediate formation between the granite and kaolin here. The genesis of these rooks may hardly be explained, because it is connected with a lot of successive superposing processes. The authors of this paper are of the opinion that the genesis of these rocks depended upon the following factors: a – differentiation of granite magma, b – cataclasic, c – influence at brown coal formation, and d – weathering processes.Among the factors mentioned above, the differentiation of granite magma was of the highest importance, being responsible for the separation of light-coloured magma with small amount of femic minerals (biotite) from the normal biotite-bearing granite magma. The consolidated forms of this latter occur as rocks that may be observed in various quarries near Strzleblów and Sobótka. The leucocrartic differentiate was strongly affected by autohydrothermal phenomena, which led to alteration procces that in turn set both sodium and SiO2 in motion.In a metasomatic way the sodium dislodged potassium and by infiltration, it pertitized, in the form of albite, the potassium feldspar. Silica caused here the silification of rocks. Simultaneously, tectonic phenomena took leading to the intense cracking the feldspar rocks. Rich rock fissures were filled with quartz which, within the Srzegom-Sobótka massif, constitutes now numerous quartz veins (in the vicinity of Sady, Krasków, Mrowiny, Morawy, a.o.). Moreover, these fissures were responsible for the development of weathering processes. The alteration process of the rocks under consideration, particularly of their top part, also depended upon the morphological depression adjacent to the elevated feldspar rocks, being affected by the brown seams found in the neighboring areas.