Fluid inclusion characteristics of hematite-bearing quartz vein from the Daenam mine, Republic of Korea

Abstract

The Daenam mine, which produced over 9250 tons of iron oxide ore from 1958 to 1962, is situated in the Early Cretaceous Yeongyang subbasin of the Gyeongsang basin. It consists of two lens-shaped, hematite-bearing quartz veins that occur along faults in Cretaceous leucocratic granite. The hematite-bearing quartz veins are mainly composed of massive and euhedral quartz and hematite with minor amounts of pyrite, pyrrhotite, mica, feldspar and chlorite. Fluid inclusions in quartz can be divided into three main types: CO 2-rich, CO 2–H 2O, and H 2O-rich. Hydrothermal fluids related to the formation of hematite are composed of either H 2O–CO 2–NaCl ± CH 4 (homogenization temperature: 262–455 °C, salinity <7 eq. wt.% NaCl) or H 2O–NaCl (homogenization temperature: 182–266 °C, and salinity <5.1 eq. wt.% NaCl), both of which evolved by mixing with deeply circulating meteoric water. Hematite from the quartz veins in the Daenam mine was mainly deposited by unmixing of H 2O–CO 2–NaCl ± CH 4 fluids with loss of the CO 2 + CH 4 vapor phase and mixing with downward percolating meteoric water providing oxidizing conditions.