경상남도 함안-군북지역의 동광화작용: 유체포유물 및 안정동위원소 연구

Copper Mineralization in the Haman-Gunbuk Area, GyeongsangnamdoProvince: Fluid Inclusion and Stable Isotope Study

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The Haman-Gunbuk mineralized area is located within the Cretaceous Gyeongsang Basin along the southeastern part of the Korean peninsula. Major ore minerals, magnetite, scheelite, molybdenite and chalcopyrite, together with base-metal sulfides and minor sulfosalts, occur in fissure-filling tourmaline, quartz and carbonates veins contained within Cretaceous sedimentary and volcanic rocks and/or granodiorite (118±3.0 Ma). The ore and gangue mineral paragenesis can be divided into three distinct stages: Stage I, tourmaline+quartz+Fe-Cu ore mineralization; Stage II, quartz+sulfides+sulfosalts+carbonates; Stage III, barren calcite. Earliest fluids are recorded in stage I and early por-tions of stage II veins as hypersaline (35∼70 equiv. wt.% NaCl+KCl) and vapor-rich inclusions which homogenize from ∼300℃ to ≥ 500℃. The high-salinity fluids are complex chloride brines with significant concentrations of sodium, potassium, iron, copper, and sulfur, though sulfide minerals are not associated with the early mineral assemblage produced by this fluid. Later solutions circulated through newly formed fractures and reopened veins, and are recorded as lower-salinity(less than ∼20 equiv. wt.% NaCl) fluid inclusions which homogenize primarily from ∼200 to 400℃. The oxygen and hydrogen isotopic compositions of fluid in the Haman-Gunbuk hydrothermal system represents a progressive shift from magmatic-hydrothermal dominance during early mineralization stage toward meteoric-hydrothermal dominance during late mineralization stage. The earliest hydrothermal fluids to circu-late within the granodiorite stock localizing the ore body at Haman-Gunbuk could have exsolved from the crystal-lizing magma and unmixed into hypersaline liquid and H₂O-NaCl vapor. As these magmatic fluids moved through fractures, tourmaline and early Fe, W, Mo, Cu ore mineralization occurred without concomitant deposition of other sulfides and sulfosalts. Later solutions of dominantly meteoric origin progressively formed hypogene copper and base-metal sulfides, and sulfosalt mineralization.