| Co-Investigator(Kenkyū-buntansha) |
FUKUOKA Masato Institution, Department : Kyuushu Univ., Fac. of Sci. Title of Position : Assist, 理学部, 助手 (70117232)
MOTOMURA Yoshinobu Institution, Department : Kyushu Univ., Fac. of Sci. Title of Position : Assista, 理学部, 助手 (20037237)
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| Research Abstract |
The present study has made physicochemical characterization on the Uchiyama granitic body, which intrudes into the Paleogene Taishu Group, and also clarified mineralization features of veins developed in both Ohfunakoshi and Sasu areas, Shimojima, Tsushima Islands, Nagasaki prefecture. In the granitic body, magmatic susceptibility values measured by means of kappermeter, KT-5, range widely from 2x10^<-6> to 922x10^<-6> emu/g. The values display zonal arrangement which forms higher magnetic susceptibility in the core of the body to lower in the peripheral part close to mudstone-rich Lower Formation of the Taishu Group. From analyses of vein structure, mineral association and ore textures on the new outcrops of the veins, mineralization features of the Ohfunakoshi area can be regarded to correspond to those of Yasuda and Taisho deposits in the Sasu area. At the southern part of Sasu, cobaltite was firstly identified in a quartz-pyrite vein at the Tenkuma Prospect. The fact suggests that Co-Bi zone can be settled between tourmaline-greisen zone and iron-sulfide zone in the sense of district zoning, and the zone probably extends to the Yora-Naiin area. Fluid inclusions in quartz of the Uchiyama granitic body show homogenization temperatures in the range of 300 to 520^ﾟ C, and salinity with 38 to 61 wt% NaCl equivalents, and those in quartz of Ohfunakoshi vein groups 220 to 380^ﾟ C and 2.4 to 6.4wt%. The fluid inclusion study of both granitic rocks and vein minerals strongly supports a genetical model that high temperatures and high saline fluids were derived from the Uchiyama granitic magma, and mixed gradually with meteoric water to form distric zoning of lead-zinc sulfide mineralizations at Shimojima, Tsushima Islands.
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