岳下炭の分析値の地質学的解析 : "佐世保炭田" 炭の地質学的研究

The author (1963) alreaay reported the general relationships between the causes of coalification and the grade of coalification of some chief coal seams in the Sasebo coal field in northwestern Kyushu. In this paper, he treated more precisely the coal specimens, which are obtained from the coal seam "Sanjaku-so" in the Takeshita Colliery. It is located in the southwestern part of the coal field, where some amounts of the most important strong-coking coal in Japan are produced. Contents of ash, moisture, carbon, and hydrogen are determined by the Japanese Industrial Standard methods (JIS M8812-and M8813-1959), and the results are shown in Table I. Variations of analyses with the geologic aspects are as follows: 1. Moisture content of the coal seam along the slope in the mine decreases at increasing depth. The average rate of decrease of moisture with depth is approximately 0. 10 % per 100 meters (fig. 3). 2. Carbon content of the ash-free-dry coal increases with depth at the rate of 0. 35% per 100 meters increase in depth, while the hydrogen decreases at about 0. 12% per 100 meters increase in depth (fig. 4). 3. The mine is divided into two sections with a fault, which has a down-throw of about 100 meters in the pit (fig. 2). Notwithstanding the throw of such amount, coal specimens on both the sides of the fault practically show the same values of moisture, carbon and hydrogen in the same depth. Having studied the relationships between variations of analyses and causes for the development of different varieties of coal, the author came to the conclusions as follows: 1. According to paragraph 1 cited above, Schlirmann's rule is applicable even to this single and dipping seam of high rank bituminous coal, while schurmann's rule stated that the water content of lignite in a given borehole decreases at increasing depth. 2. The author (1963) has made a revision on the definition of Hilt's law as follow; "carbon content increases with depth along slope of a mine in a single coal seam", while Hilt's law stated in a given shaft or a given borehole, volatile matter decreases at increasing depth. Then, Hilt's law in revised definition is found really applicable for this coal seam. 3. Variations of contents of moisture, carbon, and hydrogen have no remakable relation to the factors producing the change of the grade of coalification, such as limited effect of heat from intrusions of igneous rocks, effects of fractures or pores in the overlying rocks, and compression resulting. from fault movements, but only have close relation with the depth of burial, which is accompanied with influence of temperature gradient obtaining in their depth. 4. It is presumed that the NW-SE trending faults, which have the same trend as the fault running across in the pit, were made after the accumulation of the Upper Miocene Oya and Fukazuki formations of the Nojima group. Therefore, the time length from the formation of those faults to the present, may be probably shorter than the time length since burial of the seam till the faults occurred. Consequently, accompanied with the evidence shown in 3 above, it is inferred that coalification might have been developed rather slowly before the faults of NW-SE trend occurred, and advanced comparatively rapidly after that time.