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内容記述 |
The occurrences of molybdenite from Gunma Prefecture, Japan were investigated. There are four localities of molybdenite in Gunma Prefecture:Minagasawa area (the source area of Tone-River),Tanig-awadake area,Shirasawa mine(skarn ore deposit)in Numata-city,and Akazawa trail in Takasaki city. At the first locality(Minagasawa area),molybdenite occurs in pegmatite or aplitic quartz vein derived from the intrusive rock(porphyritic granite),with quartz,plagioclase,K-feldspar(altered),chlorite after biotite,epidote and a small amount of pyrite, chalcopyrite, apatite and zircon. At the second (Tanigawadake area), molybdenite occurs in aplitic quartz vein including slender fragments of altered plutonic rock which contains quartz, feldspar(albite?),plagioclace(altered),muscovite,calcite,chlorite and a small amount of pyrite, magnetite(?),chalcopyrite,zircon and rutil. Molybdenite from Shirasawa mine shows two different occurrences:one occurs in compact magnetite ore with hedenbergite,and the other occurs as very tiny molybdenites dispersed in leucocratic rock with pods of amphibole and pyrrhotite. Molybdenite from Akazawa trail occurs in the pyroclastic rocks(propyrite)which has undergone extensive hydrothermal alteration(silicification),with quartz,kaokinite,sericite,natroalunite(or minamiite?),native sulfur and a trace amount of rutil,marcasite, pyrophyllite(?)and tourmaline(greyish blue～greiysh purple). \nAll molybdenites from Gunma Prefecture are 2H1 type, according to their X-ray powder diffraction patterns. The unit cell constants of molybdenites from Minagazawa, Tanigawa dake, Shirasawa mine and Akazawa trail are as follows:a＝3.1619(2)Å、c＝12.305(2)Å、V＝106.53(2)Å;a＝3.1610(2)Å、 c＝12.299(2)Å、 V＝106.42(2)Å;a＝3.1600(2)Å、 c＝12.299(4)Å、 V＝106.36(4)Å;a＝3.1605(6)Å、 c＝12.287(5)Å、V＝106.29(6)Å,respectively. The unit cell constants of native sulfures and natroalunites (or minamiites?)are also reported. |
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