Lead-Zinc Mineralization and Related Granitic Rocks, Tsushima Islands, Nagaski Prefecture

Research Project

Project/Area Number	01540664
Research Category	Grant-in-Aid for General Scientific Research (C)
Allocation Type	Single-year Grants
Research Field	鉱物学(含岩石・鉱床学)
Research Institution	Kyushu University
Principal Investigator	SHIMADA Nobutaka Institution, Department : Kyushu Univ., Fac. of Sci. Title of Position : Professor, 理学部, 教授 (00037235)
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)
Project Period (FY)	1989 – 1990
Project Status	Completed (Fiscal Year 1990)
Budget Amount *help	¥700,000 (Direct Cost: ¥700,000) Fiscal Year 1990: ¥700,000 (Direct Cost: ¥700,000)
Keywords	Tsushima Islands / Granitic rocks / Magnetic susceptibility / Fluid inclusions / Lead-zinc mineralization / Cobaltite / 鉱脈 / ゾ-ニング / 対馬内山花こう岩体 / 流体含有物 / 花こう岩類
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.