COMPOSITIONAL VARIATION OF ARSENOPYRITE AND FLUID EVOLUTION AT THE ULSAN DEPOSIT, SOUTHEASTERN KOREA: A LOW-SULFIDATION PORPHYRY SYSTEM
COMPOSITIONAL VARIATION OF ARSENOPYRITE AND FLUID EVOLUTION AT THE ULSAN DEPOSIT, SOUTHEASTERN KOREA: A LOW-SULFIDATION PORPHYRY SYSTEM
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韩国东南部蔚山矿床毒砂的成分变化和流体演化：低硫化斑岩系统
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发表时间：
2000
期刊：
影响因子：
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通讯作者：
Seung
中科院分区：
文献类型：
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作者：
S. Choi;Seung
蔚山铁钨矿位于韩半岛东南边缘的白垩纪庆尚火山沉积盆地内。不同的热液活动导致钙矽卡岩和脉状沉积物在第三纪花岗岩附近的重结晶石灰岩中形成。蔚山矿区的矿床提供了一个独特的机会，可以从地球化学角度记录与低硫化系统有关的矽卡岩-脉系统的复杂演化。花岗岩与重结晶灰岩接触处存在无水Ca-Al-Mg矽卡岩矿物，显示了早期矽卡岩阶段（I期）的等化学接触变质作用。在主进行矽卡岩阶段（II期）磁铁矿沉积后，毒砂的第一次沉积与闪辉石-镍云母-革辉石-滑石-天然铋-铋黄铁矿-六方磁黄铁矿共生。这些常见的硫化物组合在矽卡岩主阶段具有整体低硫化度的特征。逆行矽卡岩（III期）的特征是白钨矿在方解石和石英中少量浸渍，并伴有放光石和绿泥石。第三阶段后期进行了铜锌和多金属硫化物成矿。最新一期热液系统（第四期）以菱铁矿-石英脉中的锌铅银成矿为特征。毒砂中As含量从第II阶段到第IV阶段下降，表明温度或硫逸度（或两者）随时间下降。不同的矽卡岩形成事件和不同阶段的矿石矿物，是由与Fe-As （-Ni）成矿作用相关的顺行矽卡岩形成时期的高盐岩浆流体向与W-Cu-Zn成矿作用相关的顺行矽卡岩形成时期的低盐低温流体演化的结果。随着岩浆源流体影响的减弱，地表流体沿裂缝下降到更深的水平，导致与锌-铅-银矿化相关的菱铁矿-石英沉积。这些结果表明，蔚山矿床可能是一个矽卡岩矿床，其成因与低硫化斑岩系统有关。
The Ulsan Fe–W mine is located within the Cretaceous Gyeongsang volcano-sedimentary basin at the southeastern edge of the Korean Peninsula. Distinct hydrothermal events resulted in calcic skarn and vein deposits in recrystallized limestone near a Tertiary epizonal granite stock. The deposits of the Ulsan mine present a unique opportunity to document geochemically the complex evolution of a skarn–vein system that is related genetically to a low-sulfidation system. Isochemical contact metamorphism of an early skarn stage (stage I) is displayed by the presence of anhydrous Ca–Al–Mg skarn minerals at the contact between granite and recrystallized limestone. Following magnetite deposition in the main prograde skarn (stage II), the first deposition of arsenopyrite occurs intergrown with rammelsbergite – niccolite – gersdorffite – lollingite – native bismuth – bismuthinite –hexagonal pyrrhotite. These common sulfide assemblages are characterized by an overall low-sulfidation state during the main skarn stage. Retrograde skarn (stage III) is characterized by minor impregnations of scheelite in calcite and quartz, with actinolite and chlorite. During the latest part of stage III, Cu–Zn and polymetallic sulfide mineralization was introduced. The latest episode in the hydrothermal system (stage IV) is characterized by Zn–Pb–Ag mineralization in siderite–quartz veins. Decreasing As contents in arsenopyrite from stages II to IV indicate a decrease in temperature or sulfur fugacity (or both) with time. The various skarn-forming events and ore minerals from various stages are interpreted to have resulted from an evolutionary trend from hypersaline magmatic fluids during prograde skarn formation associated with Fe–As(–Ni) mineralization to low-salinity and low-temperature fluids during the retrograde skarn formation, associated with W–Cu–Zn mineralization. As the influence of magma-derived fluids waned, surficial fluids descended to deeper levels along fractures, resulting in siderite–quartz deposition associated with Zn–Pb–Ag mineralization. These results demonstrate that the Ulsan deposit is likely a skarn deposit that is genetically related to a low-sulfidation porphyry system.