Łupki łyszczykowo-syderytowe z Olesznem Podgórskiej na północnym brzegu bloku izerskiego

Teresa Oberc-Dziedzic

Abstract


 Wykazano, że drobnoziarniste łupki łyszczykowo-syderytowe mają wysoki stopień metamorfizmu (występowanie biotytu), czym różnią się od sąsiadujących z nimi łupków kompleksu kaczawskiego. Na podstawie badań przedstawionych w artykule zaliczono je do kompleksu izerskiego.

 

MICA-SIDERITE SCHISTS FROM OLESZNA PODGÓRSKA, NORTHERN MARGIN OF THE IZERA BLOCK

 

Quartz rock occurs at the boundary of fine-grained granites and mica schists north of Oleszna Podgórska near Lubomierz. In connection with demonstrating resources of the rock, four drillings were made in its proximity (Fig. 1). Two drillings (no 3 and 2a) entered mica schists beneath the quartz rock, one drilling (no 2b) – beneath granite and. the quartz rock, and the last one (no 2) – just below the surface. The schists are dipping southwards beneath the granites.

It is possible to differentiate several varietes of schists: quartz-albite-muscovite-siderite, quartz-alhite-muscovite-biotite, quartz-muscovite-siderite-pyrite and biotite schists with siderite. All the varietes are fine-grained and excellently laminated.

Depending on the variety, it is possible to distinguish quartz, quartz-albite, mica and siderite laminae. Siderite occurs in laminae parallel to those formed of other minerals or, sometimes, along axial planes of small folds. Pyrite is often concentrated in bends of folds and is primarily related to quartz-muscovite-siderite-pyrite schists. It should be emphasized that calcite is absent and that neither traces of feldspatization nor supply of other elements were found here. There are transitions between all the varietes of schists and lithological boundaries between the varietes are dipping at the angle of 60-70° and are parallel to the lamination.

The schists are intensively folded (PI. I, Figs. 2–3; PI. Il, Fig. 4). Isoclinal and disharmonic folds are most common here.

The nature of these schists suggest that their ratios are preserved unaltered since the sedimentation. The mineral composition indicates that clay shales and siltstones formed in the siderite-pyrite facies were parent rocks of these schists.

Concentration of siderite could have taken place during the sedimentation or at the beginning of diagenesis.

Siderite-bearing mica schists markedly differ from both the Izera and Kaczawa schists. They differ from the former in being very fine-grained, the lack of potassium feldspar, omnipresence of siderite and the style of deformations, and from the latter in more advanced metamorphism and resulting presence of biotite which, up to the present, is not known from the Kaczawa schists. Weakly metamorphosed Kaczawa schists were found in the waste and innumerous outcrops in the proximity of rocks described here so the latter should be considered as related to the Izera complex. If this is the case these rocks would represent equivalents of the schists from Pilchowice and occur at the boundary of the Kaczawa and Izera complex.

Siderite-bearing mica schists do not display traces of thermal effects of neighbouring fine-grained granites which igneous nature is still to be proved. The metamorphosis of schists took place during strong differential movements and the crystallization did not continue after the deformations. The metamorphism conditions are determined by the occurrence of biotite on the one hand and the persistence of siderite on the other hand.

 


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DOI: https://doi.org/10.7306/gq.v22i1.8866