石狩炭田芦別炭の鉱物組成 4. 主要無機元素と鉱物組成との関係 Mineralogical composition of the Ashibetsu coals in the Ishikari coalfield. 4. Relationships between major inorganic elements and mineralogical composition.
The major inorganic elements (Si, Al, K, Ti, Na, Mg, Ca, Fe, Sr, P, F, and Cl) and total sulfur in seven Paleogene coal seams of the Ashibetsu colliery in the Ishikari coalfield, Hokkaido, were analyzed and the contents were compared with their mineralogical composition. The results show that the contents of all of these elements except Cl well reflect the abundance of the minerals containing each element in the coal seams.<BR>The high correlation coefficient between any pair of ash content, Si, Al, K, Ti, and Na indicates that these five elements are associated with silicate minerals. The correlation coefficient between Si and ash content is the highest because Si is contained in quartz and all aluminosilicate minerals in the coal samples. Most of the Al is associated with aluminosilicate minerals, although a minor fraction is also associated with goyazite and boehmite. K is contained as an interlayer cation in illite, K-smectite, and/or illite/smectite mixed-layer clay minerals. Ti is thought to substitute for Al in aluminosilicate minerals, especially in clay minerals. The content of Na reflects the existence of Na-bearing minerals such as plagioclase, smectite, and illite/smectite mixed-layer clay minerals.<BR>Mg is mostly associated with carbonate minerals and partly with Mg-bearing clay minerals. Mg correlates well with ash content for the coal samples containing Mg-bearing clay minerals such as illite, smectite, K-smectite, and illite/smectite mixed-layer clay minerals. Most of the Ca exists as calcite and ankerite, although part of the Ca exists also as apatite, dolomite, and plagioclase. The great abundance of ankerite resulted in the relatively high correlation coefficient between Ca and Mg. Fe is divided into Fe in carbonate minerals and Fe in pyrite and iron sulfate minerals. Fe correlates well with Mg for the coal samples containing Mg-bearing siderite. The high correlation of Fe with S is caused by several samples which contain a higher amount of pyrite and iron sulfate minerals.<BR>The average contents of Ca, Mg, and Fe in the coal samples containing only calcite and ankerite as Ca, Mg, and/or Febearing minerals are estimated to be nearly the same as those in recent plants or peats. This result implies that Ca, Mg, and Fe in both calcite and ankerite originate from organic material of peats.<BR>The correlation of Ca with P for the coal samples relatively rich in apatite is high, indicating that significant amount of Ca exists as apatite. P occurs as apatite and goyazite, and Sr occurs as goyazite only. As P and Sr also show a high correlation coefficient, these two phophate minerals are thought to be closely related in origin. Apatite is thought to appear mostly as fluorapatite since most of coal samples contain enough F to form fluorapatite. The remainder of F is believed to be organically bound.<BR>Both inorganic and organic chlorine appear to exist though the content of Cl is low in the coal seams. Inorganic chlorine is thought to be incorporated into the coal seams by clay minerals because the correlation coefficient between Cl and both Na and ash contents is relatively high. Up to about 0.01% of the Cl appears to be organically bound.
資源地質 46(1), 13-24, 1996-02-28
The Society of Resource Geology