Mineralogy and petrography of the two Lower Eocene lacustrine coals, Sorgun and Suluova, Turkey

Karayigit A. İ., Gayer R., Cicioglu E., Eris E.

INTERNATIONAL JOURNAL OF COAL GEOLOGY, vol.34, pp.111-130, 1997 (SCI-Expanded) identifier identifier


Coal reserves of Lower Eocene age are limited in Turkey and the most important are situated in the Sorgun and Suluova basins. A thick and laterally extensive coal seam occurs at the base of the Celtek Formation in the two basins. The Celtek Formation was developed in a fluvial-lacustrine facies and was unconformably overlain by transgressive units of Middle-Upper Eocene age. The coal samples were studied mineralogically and petrographically, and to define fluorescence emission spectra of sporinite and cutinite. A total of 75 coal samples collected from the two basins are characterized, on an air-dried basis, by relatively low moisture contents (0.69-9.31 wt%, av. 3.90 wt%), a broad range of ash yields (2.4-67.8 wt%, av. 19.9 wt%), total sulphur contents (0.55-7.60 wt%, av. 2.15 wt%), and calorific values (1689-7480 kcal/kg, av. 5458 kcal/kg). Minerals of the coals from the two basins determined on an air-dried basis by X-ray diffraction method are mainly kaolinite, quartz and pyrite. Kaolinite and pyrite contents of the Sorgun coals are higher and quartz contents are lower than those of the Suluova coals. In addition, a few samples in the Sorgun coals contain epigenetic calcite, whereas some samples in the Suluova coals contain syngenetic siderite, calcite and dolomite. The coals in general are characterized by high contents of macerals of the huminite group (av. 69.0 vol%), and contain liptinite (av. 4.9 vol%), inertinite (av. 0.8 vol%) and mineral matter (av. 25.3 vol%). On the TPI and GI diagram the coals plot in the limno-telmatic and telmatic areas in which the Sorgun and Suluova peats accumulated between the high and low water tables. Fluorescence emission spectra of sporinite and cutinite macerals are, in general, similar in the coals of both basins, but the spectral maxima of sporinites and cutinites are between 594-658 nm and 592-671 nm respectively. The values for the sporinites indicate a relatively broad range of coal rank. However, the range of values of the mean random ulminite (mainly eu-ulminite A) reflectances (0.46-0.60%Rr, av. 0.53%Rr), the proximate and ultimate analyses imply that the rank is a subbituminous A coal transitional to high-volatile C bituminous coal according to the ASTM classification. (C) 1997 Elsevier Science B.V.