Influence of Tectonic Dislocations on Oil Shale Mining in the Estonia Deposit

Abstract

Three linear tectonic dislocation groups of different orientation (and probably also of different age) cut the Estonian oil shale-kukersite deposits. Two younger groups of structures are typical fault zones with N-NE and NW trends, which are expressed topographically as narrow valleys, partly infilled by till, both on land and offshore. The oldest, third group of structures is represented by narrow, somewhat curvilinear, NE-trending folded and fractured zones, associated with extensive dolomitization, hydrothermal mineralization and karst. Oil shale within these structural zones is oxidized and partly replaced by karst clay. All dislocations disrupt and complicate the structure of deposit, which affects mining conditions from the technical point of view and also causes a loss of oil shale resources.

Surface Mining Technology in the Zones of Tectonic Disturbances, Estonian Oil Shale Deposit

“…The Estonian oil shale deposit, which was formed about 458-456 Ma ago, constitutes a 135 km elongated lens-shaped body of EW direction in the lowermost part of the Kukruse Stage of the Upper Ordovician limestone bedrock in NE Estonia [1]. In its eastern part near the Estonian-Russian borderline on the Narva River the width of the deposit is about 45 km, which gradually narrows down to 10-15 km in the westernmost part [3,4]. The economic bed is cropping out 5-10 km to the south of the shoreline of the Gulf of Finland, in the 1.5-2 km zone, and dips gently to the south, about 2.9 m per km.…”