Tefenni (Burdur) Linyitlerinin Mineralojik Petrografik Özellikleri Ve Oluşum Ortamlarının İncelenmesi

Abstract

This thesis aims to investigate the mineralogical-petrographic properties and formation environments of coals in the Tefenni Basin (Burdur, SW Türkiye). Palynological, mineralogical, geochemical and Rock-Eval pyrolysis analyses were also carried out within the scope of the thesis. The investigated coal seams were cored at the deepest parts of the exploration wells and are located within the lacustrine units. The Tefenni Basin is NE-SW trending and is approximately 60 km long and 10-20 km wide. A total of 46 samples were obtained from four exploration wells, which were collected from the mostly lacustrine sedimentary sequences of the basinal infilling; 42 of them are coal, clayey coal, coaly siltstone/claystone/shale, carbonaceous claystone samples, and 4 of them are clayey limestone containing trace organic matter. In addition, rock samples were obtained from the AK-43 well, which has a total depth of approximately 452 m from beneath the surface, in order to determine the vertical mineralogical distributions. Furthermore, palynological studies were performed on selected samples from the AK-44 well, which firstly identify the Early Pliocene age for coal seams. The weighted means of total moisture on an as received basis is 37.4%; on an air-dry basis (adb) volatile matter is 43.3%, ash is 31.0%, total S is 2.66%, total C is 37.56% and upper calorific value is 3407 kcal/kg. According to XRD-whole data, clay minerals, quartz, calcite, aragonite, dolomite, pyrite, and feldspar are detected in most of the coal, clayey coal, coaly siltstone/claystone/shale, and carbonaceous claystone samples, and gypsum and opal-CT were identified in a few samples. The identified minerals were also determined in rock samples examined from the AK-43 well. In all of the examined samples, huminite constitutes the important maceral group on a mineral-free basis (mmf). Liptinite and inertinite display low proportions. The random mean reflectance (%Rr) and standard deviations of ulminite reflectances were measured as 0.29%±0.03. The rank of samples are low-rank (lignite) based on average values of gross calorific values and %Rr values of samples. Tmax values vary between 421 and 437°C, which are compatible with the rank of the samples and indicate a low degree of coalification. Comparing the elemental compositions of selected coal and clayey coal samples from the AK-44 well with world low-rank coal averages, Ni is the only slightly enriched element, while the averages of Ba, Co, Cr, Li, Pb, Se, V and Zn are close to the world low-rank coal averages. Beside, As, B, Cu, Ga, Mo, Rb, Sr, U and Y are depleted. Within the scope of the study, SEM-EDS studies were performed on selected polished blocks. A part of detected minerals in XRD, several accessory minerals in micron sizes (e.g. biotite, sphene, Ti-oxide, ilmenite, Fe-Cr-oxide, F-apatite and florencite), fossil shell fragments with CaCO₃ composition, silica (diatom and sponge spicules?) and biogenic residues with Ca-phosphate composition were observed. In addition, traceable amounts of Mn were also detected from carbonate minerals and especially pyrite grains. According to coal facies, palynology and diatom studies in the Tefenni Basin, precursor peats were developed under lake-shore (limno-telmatic) and occasionally wet forest (telmatic) mire conditions, where neutral-weak alkaline conditions prevailed, similar to the Pliocene coal formations in Southwestern Anatolia.