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Trace elements in the Lower Pliocene fossiliferous Kangal lignites, Sivas, Turkey

International Journal of Coal Geology
Publication Date
DOI: 10.1016/s0166-5162(01)00030-1
  • Quality
  • Mineralogy
  • Trace Elements
  • Lignite
  • Tuff
  • Kangal
  • Turkey
  • Earth Science


Abstract The Kangal lignite basin, which is one of the most productive lignite basins in eastern Anatolia-Turkey, includes two lignite seams containing abundant gastropoda shells in the Lower Pliocene Kalburcayiri Formation. The seams are currently exploited in an open-cast mine in the Kalburcayiri field and supply feed coal to a power plant with 300-MW capacity. The average thickness of each of the two seams in this mine is about 10 m, and they are separated by about 20 m of tuffaceous sedimentary rocks. A 15–20-cm thick tuff bed occurs within the upper seam. The purpose of the study was to understand mineralogy and trace element concentrations of the two lignite seams in the Kalburcayiri Formation which were affected by volcanic ashes. Fifty-nine core samples of the lignites from seven boreholes across the basin, and eight channel samples from the working lignite seams were collected and analysed by proximate analysis, X-ray powder diffraction (XRD), inductively coupled plasma–mass spectrometry (ICP–MS), and scanning electron microscopy (SEM) with energy-dispersive X-ray microanalysis techniques. The samples show that the worked lignite seams, on an as-received basis, contain high moisture contents (43.4–57.8%). All the samples on an air-dried basis have high ash yields (from 19.5% to 81.7%) and a broad range of total sulfur contents (from 1.16% to 7.04%), and calorific values (684 to 4621 kcal/kg), except for two samples with no temperature rise due to high ash yield. The mineral matter of the studied samples is made up of calcite, quartz, feldspar, pyrite, opal-CT, clay minerals, gypsum and traces of aragonite. The trace element analyses, on a whole-coal dry basis, indicate that most of the borehole samples showed enrichment in specific elements, including Zn (15–1394 μg/g), Mo (13–368 μg/g ), and U (5.5–131 μg/g), when compared to the range of these elements for most coals in the world. The contents of Zn, Mo, and U for the samples from the worked lignite seams are, respectively, 38–187, 54–161 and 28–55 μg/g . The SEM studies show that Zn is hosted mainly in micron-sized Zn-bearing mineral (sphalerite), but no Mo- and U-bearing minerals have been detected during these studies, except for monazites containing Th and U traces. The Mo and U concentrations are negatively correlated with the ash yields, and these elements are contained mainly within organic matter.

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