Fałdy i spękania w skałach dolnocechsztyńskich na obszarze szybu wschodniego kopalni Lubin

Józef Oberc, Wojciech Salski

Abstract


FOLDS AND FRACTURES IN THE LOWER ZECHSTEIN ROCKS NEAR THE EASTERN SHAFT OF THE LUBIN MINE

Summary

The copper ore deposits recently discovered in the vicinity of Lubin, occur within both the Weissliegendes, and the copper-bearing shales of Lower Zechstein age, which belong to the Fore-Sudetic (Wroclaw) monocline. This unit rests on crystalline basement. From the Sudetic block it is separated by the Middle Odra river fault that runs in a WNW-ESE direction. The monocline is built up of the Rotliegendes (300 m), Zechstein (approximately 250 m) and Buntsandstein (about 200 m) deposits. These formations are discordantly overlain with the limnic Neogene deposits, which also cover the Middle Odra river fault and the remaining faults found in the area here considered. The beds of the Permo-Mesozois series, dipping at an angle of 2–6° towards north-east, are cut by numerous faults characterized by a WNW-ESE direction (dislocation system of the Middle Odra river), WE direction and NS direction. The fold tectonics of this area is a result of the influence of Laramie activity.
Tectonical observations made in the mine workings situated NW of Lubin have demonstrated that at the zone of the copper-bearing shales, particularly in the so-called pitch shales, are found drag folds, the axes of which run mainly in a NW-SE direction to plunge towards north-east. On the post-diagenetic sliding planes there are found scratches (A-lineation) running NNE-SSW, perpendicularly to the axes of the drag folds. These latter, and the sliding scratches have developed within an in competent bed with some thick series of competent rocks at the bottom and at the top. Apart from these fine structures related to the Laramie phase (BLa, ALa) there are found also broad anticlines and synclines whose axes can hardly be measured at present.
Discontinuous deformations are represented here by fractures and faults. The densest fracture system cuts the copper-bearing shales, the thinnest one – transects the Weissliegendes deposits. The fractures are arranged in 4–5 systems. The present authors relate them to two bc systems of various age (WNW-ESE and NW-SE systems). The age of these systems corresponds to that of the ac fracture system (NNE-SSW and NE-SW). Two bc systems are in, accordance with the directions of the Laramie structures in the North-Sudetic synclinorium and the Szczecin–Lódź–Miechów synclinorium. Most probably, the structures of the crystalline basement of the monocline considerably affected the development of the fractures in the Lower Zechstein series. Besides these systems, the carbonate series reveals fractures characterized by a W-E direction only. Both NW-SE and WNW-ESE fractures, rarely other systems, are accompanied by ore veins (chalcosine, chalcopyrite).
The BLa fold axes run parallely to the bc fracture system distinguished by a NW-SE direction. On the other hand, the fracture system of a WNW-ESE direction is perpendicular to the sliding scratches ALa.
The fault systems presented in Fig. 1 are parallel to the respective fracture systems, except for the faults characterized by a N-S trend, which do not have any equivalents in fracture directions. The fractures are related to the vertical and tangent movements of various age, i.e. to the Laramie phase, the Mesozoic movements and, even the Upper Permian movements of the sea bottom in the rocks which, at that time, were already lithified.

 


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