The geological aspects of meta-lignite and sub-bituminous coal occurrences in Poland within the context of deposits and uneconomic occurrences in Europe

Two types of brown coal can be distinguished in Poland - “soft brown coal” and “hard brown coal”, the latter being of higher rank. Hard brown coal is divided into dull and bright types. This division is based on an increasing degree of coalification (rank). According to globally recognized nomenclature for coal technology, brown coal is categorized as a low rank energetistic raw mineral with the release of low-rank C ortho-lignite (soft brown coal), low-rank B meta-lignite (dull brown coal), and low-rank A sub-bituminous coal (bright brown coal - ECE UN/50, ISO-11760). In Poland and Europe, ortho-lignite is an essential energetistic raw mineral. Its share of the energy balance of many EU member states is considerable. Deposits of ortho-lignite in Poland and Germany are among the largest in Europe, and together they comprise the Atlantic Hemisphere of brown coal deposits. In contrast, deposits of meta-lignite and sub-bituminous coal in Europe, despite its numerous occurrences, are rather small. In the balance sheet of European countries, it is not an attractive raw mineral. In Europe, deposits of meta-lignite in Mesozoic sediments appear frosted. Marine conditions of the sedimentation of these rocks were not conducive to the deposition of coaly sediments. There were only periods of marine regression in certain epochs (brakish sediments), such as the Late Triassic (Rhaetian, Keuperian), Early Jurassic, Doggerian, and a few Cretaceous periods. From these periods numerous but small deposits of coal, or just its natural occurrence, have been preserved. Coal deposits of Mesozoic meta-lignite are mostly in the formof cratonic construction. They are characterized by thin coal formations containing a small number of coal seams, which, however, can be thick and can have a good technological quality. The most famous European meta-lignite deposits are Fuveau-Di Larzac (France), Hagenes (Sweden),Moravska Trebova and Sokolovo (Czech Republic), and Belgorod-Obojansk (Russia). Also entered into the European register of deposits are the Mesozoic Polish deposits Zawiercie in the Krakow Monocline and the northern part of the Holy Cross Mts of the Kamienna river region. Coal deposits of the Cenozoic Period of dull (meta-lignite) and bright (sub-bituminous coal) types in Europe aremore numerous. Their genesis ismostly orogenic, related to the final stages of formation of themountains of the Alpine system. There are small deposits of coal formed in the intermountain and foredeep tectonic zone. Igneous phenomena of orogenic systems in general are the cause of a higher rank and higher quality coal. Well known deposits of meta-lignite and sub-bituminous coal are located in the Alps and Apenines - Monasgue (France), the Piemont-Ligurian Riviera (Italy), Hirschberg and Meissner (Germany), the Carpathian Mts localites of Ajka and Tatabanya (Hungary), Silwaniei and Petroºani in Romania, the Carpathians region in Ukraine, and also in the Balkans foredeep (Pirin and Perni in Bulgaria). There are a few Polish deposits in this period. They occur in the local intermountain basins in the Carpathians (Orawa and Nowy S¹cz Basins), in the Sudetes Mts (e.g. Lusina- Udanin, Strzegom), and in the Carpathians foredeep. These are mostly small deposits of ortho-lignite. The exceptions are the non-industrial coal deposits Grudna Dolna and the lower parts of the deck in the Orawa-Nowy Targ Basin (Lipnica Wielka), representing mainly meta-lignite. As mentioned, there are few instances of Polish meta-lignite and sub-bituminous coal and they have no economic importance. Their classification has been carried out according to rank on the basis of existing Polish documentation as well as works of its studies. The main criterion for ranking the coal was random reflectivity (Rr o) and petrologic characteristics. Coal from 0.33 to 0.40% (random reflectivity) is considered to bemeta-liginite, with coal from 0.41 to 0.50% considered to be sub-bituminous coal. In Poland, 20 regions were found. The register covers the Mesozoic deposits platform (rarely to the Cenozoic period) and orogenic deposits mostly to Cenozoic, not having the characteristics of coaly formations (e.g. the Carpathian Flysch and the Podhale Flysch sediments, southern Poland). Coal in this rank has no economic significance in Poland. However, it is an important element in the cognitive theory of coalification.