Mineralogy and Geochemistry of Feed Coals and Combustion Residues from Tunçbilek and Seyitömer Coal-Fired Power Plants in Western Turkey

This study focuses on the enrichment of elements in feed coal (FC) and combustion residues, namely, fly ash (FA) and bottom ash (BA) samples, picked up from the Tunçbilek and Seyitömer coal-fired power plants in western Turkey. The FCs in both plants have generally similar mineralogical compositions, although siderite and dolomite are more prominent in Tunçbilek and feldspar and pyrite are more abundant in Seyitömer. Minerals in the FA from both power plants are mainly quartz, hematite, magnetite, anhydrite, and mullite. Along with quartz, the Fe-oxides are dominant phases in the BA samples. Accessory minerals in the FCs, FAs, and BAs, such as chromite and pentlandite, were identified by combined scanning electron microscopy–energy dispersive X-ray analysis. Significant enrichments of Cr and Ni were detected in FCs, FAs, and BAs from both power plants. These enrichments are probably associated with pyrite, chromite, and pentlandite. Mercury was also significantly enriched in the Seyitömer FA, owing to Hg retention by chars and anhydrite. The Hg and Cl concentrations of char samples from FAs of both power plants indicate that Hg and especially Cl concentrations are much higher than those in the FCs

The genesis of the carbonatized and silicified ultramafics known as listvenites: a case study from the Mihaliccik region (Eskisehir), NW Turkey

The Mihaliccik region (Eskisehir) in NW Turkey includes an ophiolitic assemblage with a serpentinite-matrix melange. The serpentinites of this melange host silica-carbonate metasomatites which were previously named as listvenites. Our mineralogical and geochemical studies revealed that these alteration assemblages represent members of the listvenitic series, mainly the carbonate rocks, silica-carbonate rocks and birbirites, rather than true listvenites (sensu stricto). Tectonic activity and lithology are principal factors that control the formation of these assemblages. Carbonatization and silicification of the serpentinite host-rock is generated by CO(2), SiO(2)-rich H(2)O hydrothermal fluid which includes As, Ba, Sb and Sr. Low precious metal (An, Ag) contents of the alteration assemblages indicate lack of these metals in the fluid. Primary assemblages of the alteration are carbonate rocks that are followed by silica-carbonate rocks and birbirites, respectively. Petrographic studies and chemical analyses suggested an alkaline and moderate to high temperature (350-400 degrees C) fluid with low oxygen and sulphur fugacity for the carbonatization of the serpentinites. The low temperature phases observed in the subsequent silicification indicated that the fluid cooled during progressive alteration. The increasing Fe-oxide content and sulphur phases also suggested increasing oxygen and sulphur fugacity during this secondary process and silica-carbonate rock formation. The occurrence of birbirites is considered as a result of reactivation of tectonic features. These rocks are classified in two sub-groups; the Group 1 birbirites show analogous rare earth element (REE) trends with the serpentinite host-rock, and the Group 2 birbirites simulate the REE trends of the nearby tectonic granitoid slices. The unorthodox REE trend of Group 2 birbirites is interpreted to have resulted from a mobilization process triggered by the weathering solutions rather than being products of enrichment by the higher temperature hydrothermal activity. Copyright (c) 2006 John Wiley & Sons, Ltd

Enrichment and distribution of elements in the middle Miocene coal seams in the Orhaneli coalfield (NW Turkey)

This study focuses on ascertaining controlling factors and differences on mineralogical and elemental contents for reconstructing palaeoenvironmental conditions of both seams applying standard coal characteristics, mineralogical, coal-petrologic, and elemental data of the Orhaneli coalfield. The studied coalfield, one of the important coalfields in NW Turkey, includes two workable coal seams, the lower with 0.5–2 m and the upper with 5–6 m in thickness, which are separated by 2–5 m thick, grayish-green limnic claystone. The floor rocks of the both seams are limnic claystones, whereas the roof rock of the upper seam is the tuffite layers-bearing lacustrine marls. Matrix and xylite-rich lithotypes are common in the upper seam, while alternations of xylite-clayey bands (detro-xylite and xylo-detritic) are common in the lower seam. The lower seam is also characterized with the presence of altered tuff layers, while freshwater gastropod shell-bearing bands were identified from the upper seam. Even though the banding character and maceral composition of the coals were invariant between the seams, there are distinct differences in mineralogy and elemental composition, that can be related to the nature of the clastic sediment influx and contemporary volcanic inputs into freshwater forested mires. The lower seam is characterized by high ash yields (%44.2–64.3, d) and relatively high concentrations of aluminosilicate-affiliated elements and REY (rare earth elements and Y). In contrast, the upper seam has relatively low ash yield, and is slightly enriched B concentration. The B enrichment in the upper seam is presumably controlled by the presence of clay mineral (e.g., illite) and clastic volcanogenic accessory minerals (e.g., apatite). Arsenic is the only enriched element in both seams due to development of anoxic conditions. Although no traceable As was detected from syngenetic framboidal pyrite grains, the contemporary volcanic inputs (e.g., air-fall ash/tephra) along with leached surface waters into palaeomires might be source for As, while the development of anoxic conditions palaeomires could cause formation of syngenetic pyrite grains. Thus, the As concentrations of the studied samples are elevated. Nevertheless, the difference on ash yields and mineralogical compositions between studied seams might be related with different clastic influx ratios and contemporary volcanic inputs, in turn, aluminosilicate affiliated elements display different concentration coefficients (CC) values in the studied seams, and high B concentrations that are not expectable for a limnic coal Besides, enrichment of Cr, V and Ni in the upper seam are controlled by clastic V-bearing chromite grains from Orhaneli chromite deposit in the adjacent area. Furthermore, the contemporary volcanic inputs into the palaeomire of the lower seam, and their alteration under anoxic conditions caused REY enrichment and the formation of kaolinite and smectite matrices of clay aggregates in coal and altered tuff layers in this seam.The authors would like to thank Turkish Coal Enterprise (TKİ) for sampling permission, and field geologists for their helps during sampling, to Mr. Arif Talay and Mr Ufuk Kibar (MTA) for his helps during FEI-SEM studies, to Prof. Dr. James Hower (University of Kentucky, Center for Applied Energy Research), Prof. Dr. Xavier Querol (Institute of Environmental Assessment and Water Research) and Prof. Dr. Kimon Christanis (University of Patras) for their constructive comments during manuscript preparation. Finally, Dr. S. Dai, the editors-in-chief, and the anonymous reviewers are also thanked for constructive comments and corrections.Peer reviewe

The Miocene Coal Seams In The Soma Basin (W. Turkey): Insights From Coal Petrography, Mineralogy And Geochemistry

The Neogene Soma Basin, western Turkey, hosts three coal seams (kM2, kM3 and kPl) and several altered tuff layers within the Miocene sequences. This study focuses on the evaluation of coal-petrography, mineralogical and elemental compositions, as well as the Rock-Eval pyrolysis of the three coal seams from Eynez, Isiklar and Denis sectors, and to identify the mineralogy of altered tuff layers within kM2 and kPl seams. The routine coal quality analyses show that coal samples from the kM2 seam are characterized by lower ash yields and total S contents, and higher gross calorific values than kM3 and kPl seams. The mineralogical composition of the bulk coal samples varies between all three seams. The statistical treatment implies that major elements in bulk coal samples such as Al, Fe, K, Mg and Na, and the vast majority of minor and trace elements have inorganic affinity. The trace element contents and elemental enrichments in the coal samples are generally changeable from seam to seam, which could be related to differences in ash yield and mineralogy. Altered tuff layers, or tonsteins were identified in kM2 and kPl seams. The tonsteins are clay rich, and certain trace elements (e.g. As and Zr) are enriched in the coal layers beneath the tuff layers in the kM2 seam. This might be related to penetration of leached pore water into these layers and precipitation of epigenetic minerals. The coal-petrography composition and the coal-facies diagrams show that the precursor peat of the kM2 seam was accumulating under telmatic, mesotrophic, anoxic conditions, whereas the water level was high and stable. The relatively low ash yields and thicker coal beds suggest a lower clastic input from the basin margins, and water table fluctuations resulted in calcareous intercalations in the kM3 and kPl seams. These imply the development of limno-telmatic conditions whereas fluvial activity affected during peat accumulation of both seams. Considering the maceral composition along with the coal thickness, coal seams in the Soma Basin might display oil generation potential; however, the pyrolysis analysis shows that the studied coal seams are mainly gas-prone and only certain coal beds have mixed-hydrocarbon generation capacity. All data presented in this study indicates that lithological features, differences in coal qualities and elemental contents in the Soma Basin were mainly controlled by changes in the depositional conditions and the detrital input during Miocene. (C) 2017 Elsevier B.V. All rights reserved.Wo