HYDROTHERMAL SOLUTION BRECCIA HOSTED CARLIN-TYPE GOLD MINERALIZATION IN PALEOZOIC TAEBAEGSAN BASIN, REPUBLIC OF KOREA

Taebaegsan basin, which is located in Ogcheon orogenic belt of Korea peninsula, is composed of low-metamorphosed Cambrian to Ordovician marine strata (Joseon Supergroup). Various carbonate hosted metal deposits as skarn, manto and vein-type are reported for long years.

Several structures were formed under the contractional tectonic settings in the basin during Triassic to Cretaceous (i.e. thrust, folds and high angle faults). Specially, hydrothermal solution breccia (Yemi-breccia) is broadly distributed at Yemi area in the basin along N-S direction (approximately 10km), and it is over lied upper Maggol limestone which part of Joseon Supergroup. Yemi-breccia is subdivided into crackle, mosaic and chaotic breccia based on textures or subdivided sulfide-matrix breccia (SM), dark silica-matrix breccia (DM), red silica matrix breccia (RM) and carbonate-matrix breccia (CM) on the basis of matrix filled mineralogy. They show gradual transformation in SM zone to CM zone. SM mainly distributes in pathway of hydrothermal fluid and it consists of pyrrhotite, chalcopyrite, pyrite, fluorite and quartz. DM and RM mainly consist of pyrite, magnetite, hematite, quartz, dolomite and calcite. Typically, RM has contains of carbonate and hematite more than DM has. CM mainly consists of dolomite and calcite.

Hydrothermal alterations such as silicification, argilization, decalcification and carbonatization are developed in the Yemi-breccia and limestone hosts. These alteration zones (tens to hundreds of meters long) shows gradual distribution. Geochemistry of breccia and altered limestone indicates Carlin-type gold mineralization, three different types of gold are occurred as follows, 1) Gold in arsenic-rich pyrite, 2) Extracted gold from substituted hematite by post-hydrothermal fluid and 3) Gold grains in host rock. EPMA analysis for pyrite, secondary hematite and limonite show 0.04 to 0.1wt% gold contents, and It shows 0.5~12wt% gold contents that FE-EPMA analysis to gold grains (0.1~10um) in not only pyrite and hematite but also host rocks.

The Yemi-breccia is formed by introducing hydrothermal fluid and meteoric fluid along some spaces such as faults and bedding plane. Carlin-type gold mineralization is mainly formed in SM and DM zones. And these data will use for exploration of bonanza as useful information.