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    冀西石湖金矿成矿流体特征

    Characteristics of ore-forming fluids of the Shihu gold deposit, western Hebei

    • 摘要: 提要:通过对石湖金矿矿石中石英包裹体的气、液相成分分析表明,石湖金矿成矿流体为富含CO2、H2O和CH4、C2H6等挥发分的K+-Na+-Ca2+-SO2-4-NO-3-Cl-体系。硫、碳同位素分析显示硫、碳来源于地幔,氢氧同位素分析则显示成矿流体为岩浆热液和大气水的混合流体。6个均一法测温数据平均为310℃,显示为中温成矿,53个爆裂法测温数据主要集中在区域320~350℃和360~380℃两个区域,成矿期大致分为两个阶段。成矿压力为20.3 MPa,成矿深度为0.75 km,lgfo2=-39.95,Eh=-0.42~-0.64V, pH=5.94~6.44,这些特征都表明矿床形成于超浅成、相对偏氧化的弱碱性成矿环境。101-4主矿体不同中段石英包裹体测温等温线图表明,成矿流体的运移方向为自矿区南端深部流向矿区北端浅部,运移方向与矿体的侧伏方向基本一致,预示矿区南端深部还有很好的找矿前景。

       

      Abstract: Abstract:Analysis of the compositions of gas and liquid phases in quartz inclusions suggests that the ore-forming fluids in the Shihu gold deposit are a K+-Na+-Ca2+-SO2-4-NO-3-Cl-system rich in organic volatiles such as CO2, H2O and CH4 and C2H6. Analysis of sulfur and carbon isotopes shows that sulfur and carbon are derived from the mantle, and hydrogen and oxygen isotope analysis shows that the ore-forming fluids are a mixture of magmatic hydrothermal fluids and meteoric water. The average of six homogenization temperature data is 310℃, indicating mesothermal mineralization, and 53 data of decrepitation temperatures mainly cluster at two ranges, namely, 320-350℃ and 360-380℃, which reveals that approximately two mineralization occurred. The ore-forming pressure was 20.3 MPa and the ore-forming depth was 0.75 km, with lgfo2=39.95, Eh=-0.42 to -0.64V and pH=5.94 to 6.44-all these suggest that the deposit was emplaced in a near-surface, relatively oxidized and weakly alkaline ore-forming environment. The vertical isothermal diagram of quartz inclusions at different levels in orebody 101-4 suggests that the ore-forming fluids moved from south to north and from deep to shallow, with the direction of the fluid movement coinciding with the pitch direction of the orebody, implying that there are very good ore prospects at depths of the southern end of the mining area.

       

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