| 概要 |
Argentian tetrahedrite has been found as large crystals attaining 1. 0x 1. 5m mi n size, in the zinc-lead-silver veins of Shigekuma and Nihongi ore deposits in Tsushima Island, Nagasaki Prefecture. Th...ey are formed in the Taishu Group of Paleogene age, consisting mainly of mudstone with some intercalations of sandstone and shale. Constituent ore minerals from the deposits are sphalerite, pyrite, tetrahedrite, chalcopyrite, bournonite, and galena, and associated with small amounts of gangue minerals, such as siderite, calcite, quartz, Fe-chlorite, and sericite. There are three kinds of occurrence of argentian tetrahedrite: (1) as tetrahedritechalcopyrite veinlets cutting sphalerite-pyrite ores, (2) as relic minerals in the massive galena with flow-like structure, and (3) as captured fragments in siderite vein. On the basis of the microscopic and field observation, the sequence of sulfide mineralization is presented from ealier to later stages as follows: sphalerite-pyrite-tetrahedrite-chalcopyrite-bournonite-galena. Bournonite occurs as a reaction rim between tetrahedrite and galena. Unit cell edges for fifteen tetrahedrite range from 10. 414 to 10. 564 A. These values are larger than those of other localities. It is inferred from crystallochemical point of view that the variation of unit cell edge is markedly affected by substitution of Ag for Cu in tetrahedrite, according to the qualitative analysis by the electronprobe microanalyser. However, any. regular relationship between the variation of a。ofthis mineral and its distribution in the ore body has not been recognized.続きを見る
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Mendeley出力
