臨溪地域의 金-銀 鑛化作用

Gold-silver mineralizations in the Imgye district

The gold ore deposits of Nakcheon, Gongyeong and Dongmyeong mine in the Imgye district are E-W trending fissure filling veins emplaced in Precambrian Jungbongsan granite and sedimentary rocks of Cambrian Yangdeog group. The K-Ar age for vein alteration sericite and vein laced muscovite are 73 and 93 Ma, respectively. Vein structure and mineralogy indicate the three distinct depositional stages: Ⅰ) basemetal sulfides and tin minerals, Ⅱ) gold-basemeatl sulfides, Ⅲ) gold-silver-basemetal sulfides. Major gold and silver ore minerals are electrum, native silver, pyrargyrite and argentite. Fluid inclusion data indicate that filling temperatures were from 350℃ to 190℃ through stage Ⅰ, Ⅱ and Ⅲ. Salinities were in the range of 0.0~9.5 NaCl eq.wt.% and do not reveal any systematic trend. Intermittent boiling of ore fluid during stage Ⅰ is indicated by fluid inclusions in quartz. Fluid pressure during stage Ⅰ which is estimated from fluid inclusions showing boiling evidence range from 50 to 100 bars. Gold ore deposits of the Imgye district were formed under higher temperatures and lower sulfur fugacities compared with the Eunchi silver ore deposits about 8 Km apart from the Imgye district.