Z petrografii skał tufogenicznych karbonu dolnego w Zarębach koło Łogowa

Abstract

ON THE PETROGRAPHY OF TUFFOGENIC ROCKS OF THE LOWER CARBONIFEROUS AT ZARĘBY NEAR ŁAGÓW (ŚWIĘTY KRZYŻ MOUNTAINS)

At Zaręby near Łagów tuffogenic rocks are exposed which have been described by H. Żakowa (1961) as to their stratigraphy and geological position. In test pit No. 2 they occur three times, in No. 3 - twice.

These tuffogenic rocks appear in argillaceo-siliceous schists with phosphorites of the Zaręby beds (Tournaisian) in the shape of intercalations of 10 cm. thickness at the most; macroscepically they resemble loosely cemented sandstones. On the other hand, a sample taken from a well at Zaręby resembles a crystalline schist of greenish-black colour.

These rocks were investigated: as to their mechanical composition (Table 1 and Fig. 1), their chemical character (Table 2), and their geochemical character (Table 3). Some components were identified by X-ray determination. The results of thermal examinations of the samples are presented in Fig. 2.

On the basis of the collected material, the. above research distinguishes two varieties of tuffites from the test pits (a vitro-crystalloclastic and a crystalloclastic variety), and a tuffstone found in the well.

As regards their petrographic character, these rocks were assigned to tuffstone and to kaolinitized tuffites corresponding to quartz keratophyres.

The author correlates them with keratophyre tuffstones from Wildenfels and Wallau (Germany) (Table 2).

In her conclusions the author suggests that the volcanic source supplying this pyroclastic material must have been located at a moderate distance from the locality where the described Lower Carboiferous tuffites occur, and that eruption must have taken place several times, each time supplying material of identical petro-graphic character of acid rock (quartz keratophyres).