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.
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.
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.
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.
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.
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.

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Sulfide and sulfate minerals in the seven Paleogene coal seams of the Ashibetsu colliery in the Ishikari coalfield, Hokkaido, were investigated by X-ray diffraction of low temperature ash, coal, shale and tuff. The distribution of total sulfur in the coal seams is compared with the occurrence of these minerals and the morphological change of pyrite.
Most of the sulfide minerals found in the Ashibetsu coal seams are pyrite. Marcasite is rare. Pyrite tends to appear near the roof or the floor of the coal seams, and the sulfide and sulfate minerals were not detected in the main part of the coal seams save one, the Torashita-sanshaku seam. In that case, pyrite and gypsum occurred throughout the seam. Total sulfur content is also very low in the main parts of all the coal seams except the Torashita-sanshaku seam. However, total sulfur content is still low in the main part of the Torashita-sanshaku seam at a different location. This evidence suggests that most of the coal seams were formed in a fresh water environment, though a few areas were formed in a brackish water environment. This suggestion is consistent with the depositional environment inferred from the clay mineral composition.
Pyrite exists as very small, microscopically observable crystals even in the coals containing less than 0.5% total sulfur (S). Framboids are rarely present in such low sulfur coals. The number of isolated, small crystals and of framboids increases as S approaches 1%. Bigger framboids and clusters of framboids appear in coals containing more than 1% S. Pyrite spheres, formed from infilled framboids, and larger pyrite spheres or larger, irregular pyrite nodules, formed from infilled clusters of infilled framboids, are often observed in coals containing more than 2% S. All the pyrites of different shapes found in the Ashibetsu coals are syngenetically formed as the result of the activity of sulfur reducing bacteria in different depositional environments.
Gypsum, szomolnokite, conquimbite, roemerite, melanterite, and hydronium jarosite were identified in some coal samples. These sulfate minerals are weathering products from pyrite. Gypsum appears in the early stages of weathering in calcite-rich coal. Iron sulfate minerals appear in calcite-poor coals from an early stage. A coal sample, rich in iron sulfate minerals, was exposed to the laboratory atmosphere for about two and half years, resulting in the appearance of copiapite and paraconquimbite. This indicates that promotion of weathering may cause the iron sulfate mineral phase to be more varied.

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