鐵岩銀鑛床의 鑛石과 流體包有物

Silver ores and fluid inclusions of the cheolam silver deposits

The Cheolam silver deposits are emplaced along the fractures in breccia dike and the Hongjesa granite. Breccia dike contains fragments of late Cretaceous acidic volcanic rocks and other fragments of various rocks distributed in the mine area. Therefore it is presumed that the mineralization was taken place in later than late Cretaceous time. Mineral paragenesis is complicated by multiple episodes of fracturing. Six distinct depositional stages can be recognized: stage Ⅰ, deposition of base metal sulfides; stage Ⅱ, deposition of base metal sulfides and silver minerals; stage Ⅲ, deposition of carbonates; stage Ⅳ, deposition of silver minerals and base metal sulfides; stage Ⅴ, deposition of silver minerals; stage Ⅵ, deposition of barren quartz. Silver minerals from the deposits are native silver, acanthite, pyrargyrite, argentian tetrahedrite, stephanite, polybasite, pearceite, allargentum, antimonial silver and electrum. Fluid inclusion studies ware carried out for stage Ⅰ, Ⅱ, Ⅳ and Ⅵ quartz and stage Ⅲ calcite. Homogenization temperatures for each stage are as follows: stage Ⅰ, from 225° to 360℃; stage Ⅱ, from 145° to 220℃; stage Ⅲ, from 175° to 240℃; stage Ⅳ, from 130° to 185℃; stage Ⅵ, from 120° to 145℃. Salinities of ore fluids were in the range of 4 and 10 wt.% equivalent NaCl over stage Ⅰ and stage Ⅵ. Ore mineralogical data of each stage indicate that temperatures are within the range of homogenization temperature of fluid inclusions and sulfur fugacities declined steadily from 10-9.7atm. to 10-18.7atm. through stage Ⅰ into stage Ⅴ.