大華 및 敦山 重石ㆍ모리브덴 鑛床의 流體包有物

Fluid inclusions of Daehwa and Donsan tungsten-molybdenum deposits

Mineralization of Daehwa and Donsan W-Mo deposits can be devided into three distinct depositional stages on the basis of mineral paragenesis and flnid inclusion studies ; stage Ⅰ, deposition of oxides and silicates ; stage Ⅱ, deposition of base-metal sulfides and sulfosalts with carbonates; stageⅢ, deposition of barren calcite and fluorite. Tungsten, molybdenum and tin mineralization occurred in stage Ⅰ. Fluid inclusion studies reveal that ore fluid of stage Ⅰ were homogeneous H₂O-CO₂ fluids containing 3.5~14.6 mol % CO₂. Minimum temperature and pressure of stage Ⅰ ore fluids were 240℃ and 500 bars respectively. Salinities of aqueous type Ⅰ inclusions in minerals of stage Ⅰ range from 3.7 to 7.6 wt. % equi. NaCl, whereas those of CO₂-containing type Ⅲ inclusions range from 0.3 to 4.4 wt. %. Temperatures of stage Ⅱ ore fluids range from 200 to 305℃ on the whole and salinities were in the range of 3.2~7.2 wt. %. Homogenization temperatures of fluid inclusions in calcite and fluorite of stage Ⅲ range from 114 to 186℃ and salinities were in the range of 0.9~4.3 wt. %. Sulfur fugacities during stage Ⅱ deduced from mineral assemblages and tamperature data from fluid inclusions declined from earlier to later in the range of 10⁻¹¹⁸~10⁻¹⁸ atm. Fluid inclusion evidences suggest that the dominance of CO₂ in ore fluid during W-Mo mineralization is the characteristic features of Cretaceous W-Mo deposits of central district of Korea compared to those of Kyeongsang basin district.