| 我国几个主要斑岩铜（钼）矿床的包裹体演化机制及成矿pH条件 |
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| 引用本文：.1985.Evolution mechanism of inclusions and metallogenic PH condition of some major porphyry copper(molybdenum)deposits in China[J].Mineral Deposits,4(3):51~60 |
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| Evolution mechanism of inclusions and metallogenic PH condition of some major porphyry copper(molybdenum)deposits in China |
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| Abstract:Besides summarizing the type, homogenization temperature, salinity, composition, fluid boiling and evolution mechanism of inclusions in porphyry copper (molybdenum)deposits of China, this paper has discussed particularly the pH condition during quartz-sericitization and potash silicate alteration. If the homogenization temperature, KCl and NaCl concentration and chemical compo- sition ot K-feldspar and sericite are obtained from fluid inclusions in those alteration zones, the pH and αK+ values of ore-forming fluids can be calculated without difficulty. The data gained in the Yulong, Masongduo and Dexing porphyry copper deposits show that at the stages of quartz-sericitization, potash-silicate alteration and the precipitation of large quantities of metalliferous ores, the ore-forming fluids had αK+ values of 0.1-2.5 mol with the average of 0.67 mol, and pH values of 4.0-4.7. The uninterrupted change of magmatic and postmagmatic fluids with the variation in temperature, pressure and composition resulted in different types and associations of fluid inclusions in minerals for different rock-forming and ore-forming stages. Above the magmatic solidus line the primary gas-inclusions with high temperature(900℃)can be found, sometimes coexisting with melting inclusions. However, at the stage most favorable for ore deposition, polyphase inclusions rich in daughter minerals are predominant; they are associated with gas-inclusions and a few liquid-inclusions, and have homogenization tempera- tures of 250-500℃. At the late stage of mineralization, the mixing with the meteoric water led to the decrease of salinity, and the temperature of fluid phase was also decreased to 200 ℃, accompanied by the evolution of liquid inclusions into biphase gas-liquid inclusions. |
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