The Disappearance of Coal Seams Recorded in Associated Gangue Rocks in the SW Part of the Upper Silesian Coal Basin, Poland

Justyna Ciesielczuk,Paweł Filipiak,Dominik Jura,Magdalena Misz-Kennan,Aniela Matuszewska,Monika J Fabiańska

doi:10.3390/min11070735

Abstract

Coal seams in the Upper Silesian Coal Basin vanish within the Carboniferous Upper Silesian Sandstone Series and below an unconformity marking the Carboniferous top surface. Changes in the geochemical, mineralogical, petrological and palynological characteristics of gangue rocks associated with the vanished seams record what happened. The observed changes could have been caused by (1) coal-seam paleofire, (2) peat combustion, (3) igneous intrusion, (4) metasomatism and/or (5) weathering. Multifaceted research on samples collected at the Jas-Mos mining area, a part of the operating Jastrzębie-Bzie Coal Mine that are representative of different geological settings in the northern and southern parts of the mining area, point to intra-deposit paleofire as the most plausible reason for the disappearance. Biomarkers enabled recognition of differences in heating duration and oxygen access. Coal seams in the south burned quickly with abundant oxygen supply. Seams in the north pyrolyzed for an extended time under conditions of limited oxygen. Though other methods used proved less sensitive, all confirmed low (100–150 °C) paleotemperature heating. Overall, the reason for the local disappearance of the coal seams, making their exploitation difficult and unprofitable, can be assigned to a variety of different processes in a complex overlapping history of variable weathering, heating due to local endogenic fires and, probably, earlier peat combustion.

Highlights

Published: 7 July 2021Coal and coal-bearing rocks in the south-western part of the Upper Silesian CoalBasin (USCB) of Early Pennsylvanian (Namurian BC) age underwent changes resulting in the partial/complete disappearance of coal seams over an area of ca 500 km2
The aim of our research was (1) to determine whether the variety of alterations seen were caused by coal-seam fire, peat fire or magmatic intrusion, (2) to investigate changes in the maceral composition, geochemistry, mineralogy and palynology of rocks associated with disappearing coal seams and (3) to elucidate any differences in coal-seam fire conditions between the northern and southern parts of the Jas-Mos minefield of the Jastrzebie-Bzie Coal Mine
Gangue rocks accompanying disappearing coal seams in different positions in the Upper Silesian Sandstone Series were collected in two sets representing the northern and southern areas of the Jas-Mos mining area of the Jastrzebie-Bzie Coal Mine, respectively

Summary

Introduction

Basin (USCB) of Early Pennsylvanian (Namurian BC) age underwent changes resulting in the partial/complete disappearance of coal seams over an area of ca 500 km. Basin (USCB) of Early Pennsylvanian (Namurian BC) age underwent changes resulting in the partial/complete disappearance of coal seams over an area of ca 500 km2 This disappearance is associated with gangue rocks of various colors, typically located above the seams. The altered, variably colored coal-bearing rocks are characterized by increased fracturing, porosity and reduction of physical and mechanical properties [6,7], all a reflection of oxidation and heating. Changes in the gangue rocks accompanying the vanishing coal seams may have been caused by weathering and thermal alteration of coal-bearing sediments locally preserved below a regional unconformity marking the Carboniferous top surface and within intraPennsylvanian disconformities [8].

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