| 浙东脉状铅锌矿地球化学热力学研究 |
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| 引用本文：.1988.A geochemical and thermodynamical study on the veinlike lead-zinc deposits in eastern Zhejiang[J].Mineral Deposits,7(4):52~64 |
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| 中文摘要:浙东脉状铅锌矿主要赋存于侏罗纪一白垩纪火山碎屑岩中，成矿地质条件相似。本文在对典型矿区主要成矿阶段矿物组合、成矿温度、矿液成分研究的基础上，对成矿的其它物理化学条件，如pH、fO2、fS等作了热力学分析与计算，并结合主要矿石矿物的溶解度资料，计算与分析了成矿过程中主要成矿元素的搬运形式及富集机理。 |
| 中文关键词:脉状铅锌矿 成矿物理化学条件 热力学分忻 浙东 |
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| A geochemical and thermodynamical study on the veinlike lead-zinc deposits in eastern Zhejiang |
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| Abstract:The veinlike lead-zinc deposits in eastern Zhejiang occur mainly within the Jurassic-Cretaceous acid pyroclastic rocks, having similar geological environInents. According to the homogeneous temperatures and freezing points of fluid Inclusions, the temperatures of the main mineralization period are about 270℃ to 330℃ for the second stage and 200℃or so for the third; the salinities of the ore-forming fluids are 7 to 11 mass percent NaCl equivalent for stage two and 3 to 4 mass percent NaCl equivalent for stage three. On the basis of the information about mineral assemblages, mineralization temperatures and com position of ore-forming fluids, thermodynamic calculation and analysis have been made for other factors of physicochemical environment, such as pH, sufur fugacity, and oxygen fugacity. For stage two, pH is 4.2 to 5.7, sulfur fugacity is about 10-11.5 to 10-8 bar, and oxygen fugacity is about 10-35 to 10-29 bar; for stage three, pH is 5.6 to 7, sulfur fugacity is about 10-11 to 10-15.7 bar, and oxygen fugacity is about 10-43.5 to 10-39 bar. Although different deposits are slightly different in sulfur fugxcity and oxygen fugacity, they are mostly in an environment dominated by reduced sulfur species.The calculated m inerogenic environments and the data on the solubilities of ore minerals enable the authors to analyse and calculate the transportation and precipitation mechanism of the main ore-forming elements. During stage two, zinc and lead were mainly transported as chloride compelexes and precipitated as a result of decrease in temperature and increase in pH of the fluids. Besides, mixing of the ore-forming fluids with a more dilute solution is possibly another reason for precipitation. In a few ore districts dominated by oxidized sulfur species, the decrease in oxygen fugacity might also have caused the precipitation of considerable amounts of ore materials. At stage three, lead and zinc were mainly transported in the form of sulfur complexes and precipitated most possibly through the decrease in temperature and increase in oxygen fugacity. The ore-forming fluids at this stage had relatively low capacity of metal traⅡsportation, suggesting the probable existence of a large and prolonged hydrothermad circulating system. |
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