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KMID : 0380319880410000045
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Journal of Korean Research Institute for Better Living
1988 Volume.41 No. 0 p.45 ~ p.56
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A Study on Reflectance, X-ray Diffraction Pattern and Stable Isotopes for Coal Samples from Major Coal Fields in South Korea
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Abstract
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Reflectance, X-ray diffraction pattern and isotope composition of eleven coal samples from seven major coal fields of Paleozoic to Mesozoic in age were studied to examine their mineral constituent, degree of coalification and graphitization. The relationships between chemical composition and degree of coalification and graphitization were also discussed.
Under microscope, these coal samples were identified to be mostly collinite of vitrinite group with subordinate fusinite and semifusinite of inertinite group. Compositional ratios of vitrinite and inertinite in volume range from 94 : 6 to 67 : 33 indicating predominance of vitrinite over inertinite by two to 15 times. The bulk of coals comprise mainly macerals. Detrital minerals, however, contained 15 to 45 percent of the total volume of coal samples.
The reflectances of vitrinite in most samples, except for a Boeun coal, are measured to be 3.5 to 4.0 Rm% indicating that these coal samples are equivalent to anthracite. This is also consistent of the data of X-ray diffraction patterns which better discriminate coal ranks than the reflectance does.
Carbon isotopic compositions of coals and coaly shales from various coal fields range from -16.3 to -25.3%, with a mean value of -22.3%. No difference of carbon isotopic composition is found in various coals with different geologic age.
It is apparent that the Najeon coal beds are getting higher in degree of graphitization with depth in the undeground. The reason for this can be attributed to a potential increase of hydrothermal alteration of the coal beds due to the quartz porphyry intrusion, by which an introduction of igneous quartz to the coal beds can be postulated to explain the gradual increase of ash contents of the coal.
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