Bozdoğan (Aydın, Türkiye) Kömürlerinin Kimyasal ve Petrografik Özellikleri

Abstract

This thesis aims to investigate the chemical and petrographical features of seams within basin infillings of the Bozdoğan Graben (Aydın, SW Anatolia). Mineralogical, geochemical, Rock-Eval pyrolysis, and palynological studies have been conducted on samples in order to make detailed discussions. The studied seams were cored by boreholes within deeper parts of the basin infillings of Bozdoğan Basin and firstly investigated in this thesis study. The Bozdoğan Basin is 15 km wide and 30 km long, and its basement rocks are mainly composed of Palaeozoic metamorphic rocks from the Menderes Massif. The basement rocks are unconformably overlain by sedimentary rocks of the Oligocene–Early Miocene Akçay Group (Karadere, Mortuma, Yenidere, and Künar/Kale formations). Akçay Group is unconformably overlain by sedimentary units of the Middle Miocene-Pliocene Muğla Group (Sekköy, Yatağan and Milet formations). The investigated coal seams in this thesis are cored in two boreholes (AB-32 and AB-33) from 300.63–406.90 m and 716.3–619.98 m beneath the surface, respectively. A total of twelve coal samples—one coaly siltstone and one carbonaceous shale sample—were obtained from two boreholes. Furthermore, a total of seventy rock core samples were obtained from AB-33, which is the deepest core (772 m beneath the surface), in order to investigate mineralogical distributions throughout the basin infillings. Coal samples are macroscopically black in colour and brittle, and cleat/fracture epigenetic gypsum/anhydrite infillings are commonly ıobserved. The palynological studies from coal samples show that coal seams are located in the Middle Miocene (Serravallian) Sekköy Formation. The average total moisture on an as-received basis is 21.6%, whereas the average values of ash yield, volatile matter, total S and C, and gross calorific values on an air-dry basis (adb) are 35.2%, 44.0%, 5.6%, 39.1%, and 3581 kcal/kg, respectively. The sulphur form analyses of high total S-bearing samples show that the samples contain extra-ordinary organic sulphur contents (avg. 5.12%, adb). The identified minerals from coal samples by X-ray diffraction (XRD) are quartz, gypsum/anhydrite, calcite, feldspars, clay minerals, dolomite, aragonite, and pyrite. Furthermore, similar minerals are identified in rock samples from the AB-33 borehole, and cristobalite and serpentine group minerals are detected in a few rock samples in this borehole. Coal petrography studies revealed that huminite is the dominant maceral group in coal samples, while liptinite and inertinite display lower proportions. The random huminite reflection values (%Rr) are measured around 0.33±0,01%. The %Rr values along with gross calorific values of coal samples (avg. 7356 Btu/lb, on a moist, mineral-matter-free basis) show that coal samples are of lignite (low-rank A). In agreement with the coalification degree of coal samples, Tmax values are between 406 °C and 430 °C. The concentration co-efficiencies (CC) of coal samples suggest U enrichments, and B, Mo, and Sr are slightly enriched.