Abstract
The Bukok hydrothermal deposits are located in the Haenam area of the southwestern part of the Korean Peninsula. This mining area is composed of Cretaceous volcaniclastic sediments, acidic pyroclastics and rhyolite lava in ascending order. In the waning stage of acidic volcanism, low temperature hydrothermal alteration occurred by a solution related to post-volcanic activity. The hydrothermal solution ascending through the conduit of a rhyolite dome altered the parent rhyolite, pyroclastics and sediments. The alteration minerals contain quartz, barite, alunite, dickite, kaolinite, illite, chlorite, calcite and pyrite, which are classified as a mineral assemblage of the "acid sulfate type". Hydrothermal alteration resulted in the loss of major components such as Fe2O3, TiO2, Na2O, K2O and MgO, the depletion of trace and rare earth elements and the enrichment of Au, Ag, As and Sb. The mobility of trace elements including precious and base metals took place due to gold mineralization associated with the hydrothermal alteration.
The δ34S values for sulfide (pyrite) and sulfates (alunite and barite) range from -3.4 to 3.5‰ and from 6.0 to 9.6‰, respectively. The difference of δ34S values indicates that the acid sulfate alteration is a primary hypogene origin. The δ18 OH2O and δDH2O values estimated from the data of dickite and illite are from -3.8 to -0.3 and -79.6 to -96‰, respectively, representing that the hydrothermal fluids are the mixture of magmatic and meteoric waters in origin. The homogenization temperature (Th) and salinity of fluid inclusions for quartz ranges from 127 to 361°C and from 0.33 to 7.87 wt.% NaCl, respectively.
The geochemical characteristics of the Bukok hydrothermal clay deposits described above are very similar to those of "volcanogenic-epithermal gold deposits".
