A fault controlled, newly discovered Eskişehir Alpu coal basin in Turkey, its petrographical properties and depositional environment

• Published in: International journal of coal geology 2015-01, Vol.138, p.127-144
• Main Authors: Toprak, Selami, Sutcu, Emine Cicioglu, Senguler, Ilker
• Format: Article
• Language: English
• Subjects: Anatolian coal; Basins; Coal; Coal mines; Deposition; Fault controlled coal basin; Faults; Funginite; Limnic coal; Macerals; Pyrite; Turkey; Turkish coal
• ISSN: 0166-5162; 1872-7840
• DOI: 10.1016/j.coal.2014.12.013

Recent findings suggest that Turkey contains about 15 billion tons of coal within its borders. A small proportion of it (NW part) is bituminous, but the rest is sub-bituminous and lignite coal. About 80% of the coals are utilized in power generation. The newly found coal field, Alpu Basin, contains about 1.3 billion tons of coal. The coal basin is a fault controlled and deeply buried basin which is close to the industrial areas in Turkey. In the studied area, there are two coal horizons in the Middle Miocene aged m2 unit. The average mineable coal seam thickness is approximately 13–14m. In order to determine the coalification degree, petrographic composition and depositional environment of the coals, petrographic and XRD analyses were conducted on coal samples taken from three boreholes which were drilled by MTA in the Eskişehir–Alpu Basin. According to the ASTM classification, the rank of the coals is sub-bituminous. Alpu coals contain two prominent types of maceral assemblages: either containing high amounts of funginites, macrinites, ulminite and gelinites, or high amounts of liptinites associated with detrital huminites (attrinite and densinites). The first type exhibits rather more homogeneous features, but the second has a more complex, mixed appearance with detrital macerals, intensive lineation, laminations and considerably higher pyrite contents. The Alpu coals contain montmorillonite, heulandite, α-quartz, pyrite, gypsum, kaolinite, illite, illite–montmorillonite, orthoclase and clay minerals which indicate variation in the pH conditions. The tissue preservation index (TPI) and gelification index (GI) indicate a limnic environment. The sample points are located between open marsh and clastic marsh areas on the TPI–GI diagram. This case indicates that the water table was variable during the coal formation. •Fault, erosion, conditions exhibited significant features in the coals.•The macerals lost their textures, with high pH conditions.•Alpu coals show two types of maceral associations.•Funginites exhibit rare images.•Macrinite associations with funginite and cutinite.