Triyas-Jura Yaşlı Tabas Kömürlerinin Kimyasal Ve Petrografik Özellikleri, Orta İran

Abstract

This thesis study aims to investigate the geochemical and petrographical properties of coals from the Parvadeh and Mazino coalfields in the Tabas Basin. This basin is in the Tabas Block of the Central Iran Region located within the Central Iran Microplate, a part of the Alpine-Himalian orogenic system. The coalfields of the Tabas Basin are positioned in the folded-trusted zones. Therefore, the objective of the dissertation is to investigate the coals and find out the controlling factors in bituminous coal-anthracite formation using various analytical methods. For this, a total of 115 coal and inorganic (roof and floor rocks, and intercalations) samples, 88 of which are from C1 and B2 seams in the Parvadeh coalfield and 27 of which are from M1, M2, and M3 seams in the Mazino coalfield, were obtained. The coal samples from the Pardevh coalfield are dull-bright black, while in the Mazino coalfields, the coal samples are very bright and metallic grey in color. The coal samples from Parvadeh and Mazino, which have ash yields lower than 50,0% on a dry basis, display average values of 1,9% and 1,2%, total moisture on an as-received basis, and 21,6% and 7,4% volatile matter, 23,4% and 9,3% ash yield, 2,5% and 2,0% total S, 71,8% and 87.8% total C, and 6450 and 7647 kcal/kg gross calorific value on a dry basis, respectively. The identified minerals from coal and inorganic samples from both Paravadeh and Mazino coalfields by XRD-whole rock are quartz, clay minerals (kaolinite, chlorite, and illite/mica), feldspars, pyrophyllite, calcite, dolomite/ankerite, siderite, pyrite, halite, apatite, and gypsum. In addition to XRD-whole rock data, micron-sized minerals (e.g., sphalerite, galena, chalcopyrite, celestine, and sulfate salts) are identified and their modes of occurrence are put forward. For the first time, epigenetic paragonite and pyrophyllite occurrences are identified in the Mazino anthracites. Vitrinite, on a mineral-matter-free basis, is the predominant maceral group and, to a lesser extent, inertinite from both Parvadeh and Mazino coals. Liptinite group macerals are barely observed in the coal samples. The random vitrinite reflectance (%Ro) values of Pardevh coals are measured between %1,23-1,35 (avg. %1,28±0,03). The range values of maximum and minimum apparent reflectance (R' max and R'min) of Mazino anthracite are %3,91-3,97 (avg. %3,94±0,08) and %2,21-2,24 (avg. %2,23±0,16). The Tmax values of Parvadeh coals range from 463 to 475 ⁰C (avg. 472 ⁰C), whereas in the Mazino coals, the Tmax values range from 606 to 607 ⁰C (avg. 606 ⁰C). Hence, the Parvadeh coals are late-mature to over-mature, and the Mazino coals are over-mature for oil generation. The Parvadeh coals display Sr-enrichment, and Li, Mo, and Cs are also slightly enriched. Nickel is the only slightly enriched element in the Mazino anthracites. According to micro-Raman measurements, the positions of the D1 bands and the full width at half maximum (FWHM) of the G band of the studied bituminous coal samples are different from the studied anthracite samples. The distinct rank difference between the studied coalfields is also interpreted in this dissertation. The Parvedeh and Mazino coalfields are located in the folded-trusted zones, and then they are presumably transferred tectonically into their recent positions. Furthermore, coal-bearing formations seem to be affected indirectly by the Palaeocene and Eocene magmatic intrusions, where they first formed and matured. Overall, this impact was possibly more effective in the Mazino coalfield, and the Parvadeh coalfield is more likely to be less affected by these intrusions.

Keywords: Tabas, Bituminous coal, Anthracite, Mineralogy, Coal petrography, Trace elements, Rock-Eval