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内蒙古乌拉山金矿田内主要出露晚太古代乌拉山群区域变质岩和规模不一的花岗岩体以及不同时代、不同种类的脉状地质体。含金矿脉中主要矿物共生组合为碱性长石、石英、斜长石、碳酸盐矿物 (方解石、白云石 )和少量金属硫化物。矿床的显著特征为碱性长石交代作用强烈 ,碱性长石也广泛产于该地区其他各种类型的岩石中。本文采用电子显微探针分析了共生碱性长石和斜长石的化学成分 ,并采用三元二长石温度模型估计了碱性长石的平衡温度。结果表明 ,第一成矿阶段的碱性长石石英含金矿脉中碱性长石的形成温度为 3 5 3℃ ,第二成矿阶段石英含金矿脉中碱性长石的形成温度为 2 81℃ ,矿脉碱性长石形成压力约为 5kbar。这些结果与同类矿石中平衡共生的碳酸盐矿物和云母类矿物的地质温度计估计的形成温度以及共生石英中流体包裹体的均一温度非常一致。因此 ,乌拉山金矿床形成和富集的温度可估测为 2 6 0～ 3 80℃ ,压力约为 5kbar。此外 ,应用二长石温度计计算了本地区区域变质片麻岩和花岗岩中碱性长石的平衡温度 ,所得温度比采用共生铁铝榴石和黑云母温度计估计的温度要低约2 5 0℃。这表明共生的铁铝榴石和黑云母的平衡温度可能代表其寄主变质岩变质期温度及寄主花岗岩原生温度 ,而区域变质岩和花岗岩中的碱性长
The Inner Mongolia Wulashan gold ore field mainly shows the Late Archean Wulashan Group regional metamorphic rocks and the different sizes of granite bodies as well as different age and different types of vein-like geological bodies. The main mineral assemblages in the gold-bearing veins are alkaline feldspar, quartz, plagioclase, carbonate minerals (calcite, dolomite) and small amounts of metal sulfides. The significant feature of the deposit is the strong exchange of alkaline feldspar. Alkaline feldspar is also widely found in various other types of rocks in the area. In this paper, the chemical composition of symbiotic alkaline feldspar and plagioclase was analyzed by electron microprobe. The temperature of ternary feldspar was estimated by using the ternary bimonthly temperature model. The results show that the formation temperature of alkaline feldspar in alkaline feldspathic quartz-bearing gold veins in the first metallogenic stage is 353 ℃, and the formation temperature of alkaline feldspar in quartz mineralized veins in the second metallogenic stage is 2 81 ℃, the formation of veins alkaline feldspar pressure of about 5kbar. These results are in good agreement with the estimated formation temperatures of geothermal thermometers and the uniform temperatures of fluid inclusions in the symbiotic quartz with the commensurate carbonate minerals and micas of similar minerals. Therefore, the formation and enrichment temperature of the Wulashan gold deposit can be estimated at 260 ~ 380 ℃ and the pressure is about 5kbar. In addition, the equilibrium temperature of metamorphic gneiss in granitic and gneisses in the area was calculated by using a dabblestone thermometer, and the obtained temperature was about 250 ℃ lower than the temperature estimated by the co-production almandine and biotite thermometer. This suggests that the equilibrium temperature of the symbiotic almandine and biotite may represent the temperature of host metamorphic rocks and the host temperature of host granites, whereas the alkaline longs in regional metamorphic rocks and granites