| 概要 |
This paper deals with the heavy minerals found in the coal seams (the Honso and the Jyoso) intercalated into the Paleogene Tertiary formations of the Miike Coal Field, Kyushu, Japan. The results of th...e analysis are summarized and the depositional environments of the coal seams are considered as follows: 1. Heavy mineral contents, kind of minerals, their frequencies and other features are shown in Table 1 and Figures 4 and 5. 2. Pyrite is authigenic and its formation is remarkable in the upper part of the coal seams and in the hanging walls as well. A very small amount of minerals other than pyrite, such as zircon (rounded and euhedral forms), tourmalines, garnet, rutile, micas, hornblende, and pyroxene etc., is included in the coal seams. Hornblende and pyroxene, which are presumed to be volcanic activity in origin, are larger in grain size and more angular in form than other detrital heavy minerals. Further more, glauconite, analcite, magnetite, and calcite etc. are also found in the coals. 3. Between the heavy mineral composition in the Honso coal seam and that in the Jyoso, such commoness is recognized as very high frequency of colorless zircon, high frequency of hornblende and pyroxene, and formation of zeolite, while a remarkable differentiation is shown between heavy mineral composition in the sandstone of coal bearing formations of the coal field and that in the coal seams. 4. Depositional environments of coals in the Miike Coal Field considered from the view point of heavy mineral composition are; Foot wall: Brackish or fresh water, and formation of abundant pyrite and of less glauconite. Coal seam: Very scearce movement of water in the sedimentary basin where the coal was formed, formation of pyrite (rather less amount) and of glauconite (very rare), low pH and low Eh condition of water, igneous activity, and nothing or rare formation of anatase. Parting: Fall of volcanic ash or sedimentation of tuffite. Hanging wall: Formation of pyrite and glauconite in a considerable amount (transgression), and end (?) of volcanic activity.続きを見る
|
Mendeley出力
