Element geochemistry of the miocene aged coals in the Alpu (Eskişehir) area

The study area is located between Kızılcaören and Çavlum villages in the Northwestern Alpu (Eskişehir). Neogene Sedimentary units are widely exposed in this region. The stratigraphic sequence is determined by exploratory wells belong to MTA General Manager. The basement rocks of the study area consist of Triassic aged metamorphic rocks and Jurassic-Cretaceous aged ophiolitic rocks. Miocene aged deposits unconformably overlies the basement rocks. The basement of Miocene, which is characterized by gravelstone, sandstone and claystone, is named m1 series. This series is conformably covered m2 series. The m2 series is composed of with gravel, green colored claystone, grey colored sandstone, dark grey, green colored siltstone and thin grained gravelstone. The m3 series, which is characterized by limestone and gravelstone, conformably overlies the m2 series and is conformably covered by Pliocene clastic units. All of the coal samples were collected from lower and upper seams. Proximate and element analyses of the samples were performed and have been evaluated. In an air-dried basis, the coal samples of R-37 (Danişment), R-70, R-145 (Çavlum), R-160 and R-194 (Sevinç) wells are 59.97, 39.8, 29.5, 43.1 and 60,7 %, respectively. Average fixed carbon contents of the samples (air dry) of R-37, R-70, R-145, R-160 and R-194 wells are in a seriatim of 14.54, 22.8, 26.9, 18.97 and 10.1 %. Average gross calorific values of air dried of the coal samples of R-37, R-70, R-145, R-160 and R-194 wells are in order of 2104, 3105, 3783, 2615 and 1794 kcal/kg. The Coals of Çavlum region have the lowest mean value of ash, the highest mean value of fixed carbon and the highest mean value of gross calorific. The R-160 well has the highest mean value of total moisture content (19.57 %) and yet the R-37 well has the lowest mean value of total moisture content (13.8 %). The R-70 well has the highest mean value of volatile matter content (30.6 %) and the R-37 well has the lowest mean value of volatile matter content (23.69 %). In the other hand, R-160 well has the highest mean value of total sulphur content (4 %) and R-37 well has the lowest mean value of total sulphur content (0.79 %). Major element concentrations of Miocene aged coals in the Alpu area were established as Na, Mg, Al, Si, P, K, Ca, Ti, Mn, Fe and S. Compared to average values of the world coals, major element contents of these three fields are in highly enriched levels. The enrichment values for Mn, P, K and Ca are less than one indicate depletion of these elements in the studied coals with respect to the upper crustal values. Whereas other major elements have high enrichment values. The ash contents of the studied coal samples showed a positive correlation with Si, Al, Fe, Ti in the Danişment field, K, Al, Si, Ti in the Çavlum field and Si, P in the Sevinç field. Some trace elements contents of studied coal samples are defined as V, Cr, Ni, Cu, Zn, Rb, Sr, Ba, Pb and Zr. The enrichment values for the trace elements of the three fields are less than 0.01, therefore, this also indicate highly depletion with respect to upper crustal values. The ash contents of the studied coal samples showed a positive correlation with V, Cr, Ni in the Danişment field, with Cr, Ni, Sr and Zr in the Çavlum field and, with Zr in the Sevinç field. These results indicate that Miocene aged coals in the Alpu basin are low rank coals. Keywords: Coal, Element geochemistry, Proximate analyses, Miocene, Alpu, Eskişehir