Coal features and depositional environment of the Northern Karapınar–Ayrancı coal deposit (Konya, Central Turkey)

Abstract

The Karapınar–Ayrancı deposit is the most significant one among the recently explored coal deposits in Turkey. The aim ofthe present study was to determine maceral, mineralogical, and elemental compositions of coal samples picked up from one borehole(DK-7) drilled at the northern part of the deposit. The coal samples display moderate to high ash yield (average 38.7%, on dry basis),high volatile matter yield (average 33.9%, on dry basis), high total sulfur (average 6.7%, on dry basis) and low hydrogen contents(average 4.8%, dry basis). Huminite is dominant, and liptinite and inertinite appear at low concentrations. The bulk coal samples containmainly quartz, clay minerals (mainly illite and chlorite), muscovite, feldspars, carbonates (calcite and aragonite), and rarely pyriteand gypsum/bassanite. The maceral and mineralogical compositions point to mesotrophic and rheotrophic conditions during peataccumulation; nevertheless, the inorganic intercalations show that peat formation was ceased several times. The petrographical andmineralogical compositions of coal seams in northern and eastern parts of the deposit could imply vegetation and water chemistrydifferences. The abundance of fossil shell-bearing layers in the studied samples could imply a slightly higher water table than this in theeastern part. In addition, higher telohuminite content might be related to a higher contribution of tree/bush peat-forming vegetationin the northern part; however, the lack of xylite-rich lithotype and the abundance of fluorinite-type resinite imply the predominance ofshrubs on the palaeomire’s surface. Overall, the precursor peat in the northern part of the deposit was accumulated under pure telmaticto limnotelmatic conditions, vegetation heterogeneity and ditches transporting inorganic material from the margins were developed onthe surface of the Karapınar–Ayrancı paleomire.