GEOLOGICAL CONTROLS ON THE MINERALOGY AND GEOCHEMISTRY OF THE BEYPAZARI LIGNITE, CENTRAL ANATOLIA, TURKEY

The raw coal from the Cayirhan mine, Beypazari basin, Turkey contains an average of 28.5% mineral matter, consisting up to 80% zeolites. The coal seam is split by a 1-m-thick tuffaceous siltstone into the upper , first (Tv) and lower, second (To) seams, which contain essentially d ifferent zeolites. The first seam contains Ca-rich zeolites (clinoptil olite/heulandite) whilst the second seam contains Na-rich zeolites (an alcime). Experimental work has shown that a Na-rich activation solutio n will produce Na-rich zeolites when the original volcanic glass is Na -rich, but will produce Ca-rich zeolites when the volcanic material is Ca-rich. It is thought that a Na-rich activation solution, derived fr om contemporaneous volcanics in the Beypazari basin, reacted with volc anic tuffs of different chemical composition to produce the Vertical v ariability in the mineral matter of the two seams. Trace element analy ses of the raw coal showed that they are enriched in As, B, Cr, Ni and Zr when compared to world-wide averages of coal. They are also enrich ed in the major elements Na and K. These elements are probably also de rived from a volcanic source. Barium and Sr show a clear affinity for analcime, whilst Li, Cr, Ni, Cu, Zn, Co and Ga show a clear affinity f or clinoptilolite/heulandite. Trace elements showing a positive correl ation with the organic matter are Mn, B, Be, Ge, Y, Zr, Nb, Hf, W and U. Manganese, U, Th, Sc, Ge and HREE (heavy rare earth elements) show correlations with phosphate. Trace elements showing correlation with b oth Fe and S contents are Co, Mo, Ta, Pb and IREE (intermediate rare e arth elements). Arsenic and V seem to have mixed affinities with sulph ides and zeolites, and organic matter and zeolites, respectively. Alth ough a proportion of the As, B and S are retained in the ash during co al combustion, due to the sorption mechanism of CaO derived from the c linoptilolite/heulandite decomposition, significant emissions of these elements may arise from the Cayirhan thermal power station due to the anomalously high concentrations of these elements in the Beypazari co al. The high total alkali metal content of these coals exceeds the rec ommended maximum for steam coal, but it is believed that sodium occurr ing in a mineralogical form such as analcime is not as likely to contr ibute to boiler fouling as organically-associated sodium.