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

Abstract

The Karapinar-Ayranci deposit is the most significant one among the recently explored coal deposits in Turkey. The aim of the 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 contain mainly quartz, clay minerals (mainly illite and chlorite), muscovite, feldspars, carbonates (calcite and aragonite), and rarely pyrite and gypsum/bassanite. The maceral and mineralogical compositions point to mesotrophic and rheotrophic conditions during peat accumulation; nevertheless, the inorganic intercalations show that peat formation was ceased several times. The petrographical and mineralogical compositions of coal seams in northern and eastern parts of the deposit could imply vegetation and water chemistry differences. The abundance of fossil shell-bearing layers in the studied samples could imply a slightly higher water table than this in the eastern part. In addition, higher telohuminite content might be related to a higher contribution of tree/bush peat-forming vegetation in the northern part; however, the lack of xylite-rich lithotype and the abundance of fluorinite-type resinite imply the predominance of shrubs on the palaeomire's surface. Overall, the precursor peat in the northern part of the deposit was accumulated under pure telmatic to limnotelmatic conditions, vegetation heterogeneity and ditches transporting inorganic material from the margins were developed on the surface of the Karapinar-Ayranci paleomire.