Gold Deposition by Boiling or Cooling Without Boiling: Genesis ofthe Sangchon Gold Deposits,Hadong Area, South Korea  

作　　者：Maeng-Eon PARK, Kyu-Youl SUNG (Department of Environmental Geosciences, Pukyong National University, Pusan 608-737, Korea) Seong-Taek YUN (Department of Earth and Environmental Sciences, Korea University, Seoul 136-701, R.Korea) 

出　　处：《Global Geology》2001年第2期139-150,共12页世界地质（英文版）

摘　　要：In order to understand the mechanism(s) of gold precipitation in the anorthosite-hosted Sangchon gold deposits in the Hadong area, Korea, chemical speciation and reaction path calculations were accomplished by geochemical modeling. The modeling consisted of three-step procedures: reaction with anorthosite, then the simple cooling of the reacted fluid, and finally the boiling of metalliferous fluid. The principal vein minerals of the Sangchon deposits consist of quartz, sericite, kaolinite, pyrite, galena, chalcopyrite, sphalerite and acanthite. The sulfide mineralization is typically zoned from pyrite (preferentially at vein margins) to galena and sphalerite (toward vein center). Electrum is intimately associated with pyrite ± chalcopyrite and sphalerite. By comparing the results of modeling with the observed mineral assemblages and paragenesis, the most appropriate evolution path of ore fluids was suggested as follow: reaction of a single fluid with anorthosite at 300℃, then the isobaric cooling of the fluid at temperatures from 250° to 100℃, and then the boiling and cooling of the fluid due to the decrease of pressure and temperature. Calculations also show that all of the observed alteration minerals formed due to fluid-anorthosite interaction at early period, whereas most of sulfides and electrum were precipitated mainly due to cooling. The abundance of gold in veins depends critically on the ratio of total base metals plus iron to sulfide in the aqueous phase, because gold is transported as Au(HS) 2 -whose solubility is very sensitive to the sulfide activity. Our results of geochemical modeling generally fit to the observed mineral assemblages and mineral composition, indicating the usefulness of numerical simulation for elucidating the genesis of gold deposits.In order to understand the mechanism(s) of gold precipitation in the anorthosite-hosted Sangchon gold deposits in the Hadong area, Korea, chemical speciation and reaction path calculations were accomplished by geochemical modeling. The modeling consisted of three-step procedures: reaction with anorthosite, then the simple cooling of the reacted fluid, and finally the boiling of metalliferous fluid. The principal vein minerals of the Sangchon deposits consist of quartz, sericite, kaolinite, pyrite, galena, chalcopyrite, sphalerite and acanthite. The sulfide mineralization is typically zoned from pyrite (preferentially at vein margins) to galena and sphalerite (toward vein center). Electrum is intimately associated with pyrite ± chalcopyrite and sphalerite. By comparing the results of modeling with the observed mineral assemblages and paragenesis, the most appropriate evolution path of ore fluids was suggested as follow: reaction of a single fluid with anorthosite at 300℃, then the isobaric cooling of the fluid at temperatures from 250° to 100℃, and then the boiling and cooling of the fluid due to the decrease of pressure and temperature. Calculations also show that all of the observed alteration minerals formed due to fluid-anorthosite interaction at early period, whereas most of sulfides and electrum were precipitated mainly due to cooling. The abundance of gold in veins depends critically on the ratio of total base metals plus iron to sulfide in the aqueous phase, because gold is transported as Au(HS) 2 -whose solubility is very sensitive to the sulfide activity. Our results of geochemical modeling generally fit to the observed mineral assemblages and mineral composition, indicating the usefulness of numerical simulation for elucidating the genesis of gold deposits.

关 键 词：Sangchon gold deposits  cooling  boiling  genesis  Hadong area 

分 类 号：P618.51[天文地球—矿床学]