Turkish Journal of Earth Sciences

The Geology and Coal Petrography of Miocene Lacustrine Lignites and Permian Bituminous Coals from the Karapinar Area, Sariz-TURKEY




Coals occur in the Karapınar area mainly within fault-bounded lacustrine Middle Miocene deposits, and locally within shales in the lower part of marine Upper Permian limestones. This study presents the geological setting, proximate analyses, mineralogical and petrographical composition, maceral-based coal facies interpretation and rank of the Middle Miocene lignites, and preliminary results of the Upper Permian bituminous coals. The lignites on an air-dried basis constitute a broad variation of ash yields (11.6-47.0 wt%, av. 28.1 wt%), relatively high total sulphur contents (1.8-4.8 wt%, av. 3.1 wt%) and low calorific values (2050-4791 kcal kg-1, av. 3505 kcal kg-1 ). X-ray powder diffraction studies of the whole coals reveal that the dominant minerals are quartz, clay minerals and pyrite. In addition, calcite and aragonite, which were derived from fossil fragments, were identified in some samples. The average maceral group composition and mineral matter content are 69.4 vol% huminite, 6.2 vol% liptinite, 8.9 vol% inertinite and 15.6 vol% mineral matter. The distribution of maceral groups in the Karapinar area suggests that the inertinite content generally increases from Sarlak mine towards Salderesi mine, whereas the huminite content decreases. This indicates that there was a relatively higher state of oxidation in the peat towards the Salderesi mine. Both the range of values (0.32-0.41 %Rr ) of mean random eu-ulminite-B reflectances and calorific analyses indicate a transition zone from lignite to subbituminous rank for the lignites. Two Upper Permian bituminous coal samples yielded, on an air-dried basis, higher amounts of total sulphur (5.6-6.9 wt%), calorific values of 5561-6149 kcal kg-1, pyrite and/or marcasite, and calcite infilling fractures, and vitrinite contents of 74.5-79.3 vol%. The mean random reflectance values (0.66-0.70 %Rr) of telocollinite suggest a high volatile bituminous coal rank which is relatively lower than the Westphalian coals located in the Zonguldak basin, NW Türkiye.

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