Journal of the Korean Society of Mineral and Energy Resources Engineers ISSN:2288-0291(Print) 2288-2790(Online) 한국자원공학회지

Within the Sobaegsan Massif, two representative mesothermal-type gold mine areas (Youngdong area and Boseong-Jangheung area) occur. The d 34S values of sulfide minerals from Youngdong area range from -6.6 to 2.3‰ (average = -1.4‰, N = 66), and those from Boseong-Jangheung area range from -0.7 to 3.6‰ (average = 1.6‰, N = 39). These d 34S values of both areas are comparatively lower than those of most Korean metallic ore deposits (3 to 7‰). Within the Sobaegsan Massif, the d 34S values of Youngdong area are lower than those of Boseong-Jangheung area. It is inferred that the difference of d34S values within the same Sobaegsan Massif can be caused by either of the following mechanisms: (1) the presence of at least two distinct reservoirs (both igneous, with d 34S values of < -6‰ and 2±2‰) for Jurassic mesothermal-type gold deposits in both areas; (2) different degrees of the mixing (assimilation) of 32S-enriched sulfur (possibly sulfur in Precambrian pelitic basement rocks) during the generation and/or subsequent ascent of magma; and/or (3) different degrees of the oxidation of an H2S-rich, magmatically derived sulfur source (d 34S = 2±2‰) during the ascent to mineralization sites. According to the observed differences in ore mineralogy (especially, iron-bearing ore minerals) and fluid inclusions of quartz from the mesothermal-type deposits in both areas, we may conclude that pyrrhotite-rich, mesothermal-type deposits in the Youngdong area formed from higher temperatures and more reducing fluids than did pyrite(-arsenopyrite)-rich mesothermal-type deposits in the Boseong-Jangheung area. However, we prefer the third mechanism than others because the d 34S values of the Precambrian gneisses and Paleozoic sedimentary rocks occurring in both areas were not known to the present. In future, in order to elucidate the provenance of ore sulfur more systematically, we need to determine d 34S values of the Precambrian metamorphic rocks and Paleozoic sedimentary rocks consisting the basement of the Korean Peninsula including the Sobaegsan Massif.