Authigenic pyrite and calcite in Harutori lake sediments: A point of view as environmental indicator
1994
Ito, T. (Hokkaido Univ. of Education, Kushiro (Japan). Kushiro Coll.)
Authigenic pyrite and calcite were found in the lake sediment of Harutori Lake. Harutori Lake is brackish water lake and the water of lake has been polluted by drainage of living. The pyrite in diameter from few to 50 micron was formed as resulting from reducing conditions produced by the decay of organisms. The morphology of pyrite was a framboidal in abundance but a cubic and an octohedral in small. Until now, the report of calcite from the bottom sediment of lake of Japan has not known on account of a little contents of calcium ion in the Japanese lake water. The calcite was in diameter from 4 to 90 micron. The size and form of aggregate of calcite showed the growing in the bottom sediments. A rhombic platy form of calcite has been observed generally and a bipyramidal solid and a hexagomal plate was known. In the diatomaceous coarse sediment at the lower part of bottom, calcite was not found and the size of pyrite grains was smaller than other pyrite from upper part of fine clayey sediments. Those occurrences probably suggest the absence of calcite is not by dissolution but unforming of calcite under unfavorable conditions. Therefore, the presence and the morphology of calcite will be able to indicate the condition of oxidation-reduction of water, bacterial activity in the bottom sediment and/or the lixuriant growth of water plants at surface of the brackish water lake
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