| 水热条件下黄铁矿吸附-还原金氯络合物的电位法研究 |
| 李肃宁
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| 导师 | 周丽
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| 2013
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| 学位授予单位 | 中国科学院研究生院
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| 学位授予地点 | 北京
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| 学位名称 | 硕士
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| 学位专业 | 矿物学、岩石学、矿床学
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| 关键词 | 水热体系
电位分析法
黄铁矿
金氯络合物
吸附成矿
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| 摘要 | 金的吸附成矿作用是表生和低温条件下的一种重要成矿机制，含金热液(尤其是金不饱和的热液)中金络合物被硫化物矿物表面吸附－还原而导致金沉淀。金的吸附成矿作用使得金的沉淀富集不再受金的溶解度所限制，而是受硫化物矿物和金络合物溶液之间的固液界面反应所控制。目前有关金的吸附实验都是在温度小于90℃的(近)表生条件下进行的，而更高温度下的实验研究尚为空白。本论文工作致力于开展热液条件下金的吸附成矿实验，获得了以下结果： (1)基于作者所在课题组拥有的多功能高压釜，建立了以硫化物矿物为工作电极和Ag/AgCl为内置式参比电极的原位电位研究方法，可广泛用于开展低温热液条件下的吸附成矿实验，为水热流体与导电性矿物之间的固液界面反应机理研究提供实验支持。 (2)运用建立的电位研究方法开展了200℃、饱和蒸汽压条件下(Au)-NaCl-HCl-HAuCl4-(NaAsO2)水流体体系中以及加入铝粉控制还原氛围条件下，黄铁矿吸附-还原金氯络合物的实验研究。实验结果表明：初始有单质金的体系中，对于黄铁矿电极的电位，不管初始金溶液的浓度如何，加入亚砷酸钠的电位均比不加的要高；对于金电极的电位，不管初始亚砷酸钠的浓度如何，初始金溶液浓度越高，则电位相对要低。初始无单质金的体系中，初始金溶液浓度相同时，含亚砷酸钠的体系黄铁矿的电位比不含的要低。这些结果可能与200℃下金氯络合物的歧化反应导致金氯络合物的类型和分布不同有关。 以上结果表明，自然界中无论是地层中存在的含金黄铁矿还是从成矿流体中沉淀形成的含金黄铁矿，都将形成含有单质金的体系，尤其对于含As(III)的成矿流体，黄铁矿的电位要更高，充当阴极更利于金氯络合物在其表面发生还原反应。本论文工作突破了已有金的吸附-还原实验低于90℃的温度条件，可为解释低温热液金矿床的形成机制提供直接证据。 |
| 其他摘要 | Gold adsorption metallogenesis is an important metallogenic mechanism at supergene and low temperature conditions. The precipitation of gold complexes is triggered by the adsorption- reduction by sulfide minerals in gold-bearing hydrothermal fluids (especially in gold-unsaturated fluids). Gold precipitation and enrichment as a result of adsorption mineralization is no longer limited by gold solubility, but controlled by the solid-liquid interface reaction between the sulfide minerals and gold complexes solution. Gold adsorption experiments are currently conducted at(near) supergene conditions with temperatures less than 90℃, however, a higher temperature experiments has not been reported. The work of this thesis is committed to carry out the adsorption metallogenesis experiment of gold chloride complexes under hydrothermal conditions. Some results were obtained as follows: (1)Based on the multifunctional autoclave developed by our research group, we built up an in situ potentiometric methods with sulfide minerals as working electrode and Ag-AgCl electrode as internal reference electrode in autoclave. This system can be widely used to carry out the adsorption mineralization experiments under low-temperature hydrothermal condition, it can also provide experimental support for the mechanism research of the solid-liquid interface reactions between hydrothermal fluid and conductive minerals. (2) We use established potentiometric methods to carry out the adsorption-reduction reaction of gold chloride complexes by pyrite in (Au)-NaCl-HCl-HAuCl4-(NaAsO2) hydrothermal fluid system with the conditions of 200 degrees celsius, saturated vapor pressure, and aluminum powder controls reduction conditions. Experimental results indicated that: for the initial metallic gold-bearing system, the potential of pyrite electrode is higher in system with the adding sodium arsenite than those without, regardless of the initial gold concentration of the solution. However, the potential of gold electrode is relatively low in system with higher initial gold solution, regardless of the initial arsenite concentration. For the initial metallic gold-free system, the potential of pyrite electrode is lower in system with the adding sodium arsenite than those without, in the same initial gold concentration solutions. This results may relate to disproportionation reaction of gold chloride complexs under 200℃ which leads to different types and distribution of gold chloride complexs. The above results suggest that, in nature system, the auriferous pyrite which exists in the stratum or precipitated from the ore-forming fluids can form a metallic gold-bearing system, and the potential of pyrite is higher especially in the As(III)-containing ore-forming fluids. This kind of pyrite can act as the cathode for the reduction reaction of gold chloride complexes on the surface of pyrite. The work of this thesis has been broke through gold adsorption-reduction experiments below 90℃ temperature conditions and provide a direct experimental evidence for explaining the metallogenic mechanism of epithermal gold deposits. |
| 学科领域 | 地球深部物质与流体作用地球化学
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| 语种 | 中文
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| 文献类型 | 学位论文
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| 条目标识符 | http://ir.gyig.ac.cn/handle/352002/5853
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| 专题 | 研究生_研究生_学位论文
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推荐引用方式
GB/T 7714 |
李肃宁. 水热条件下黄铁矿吸附-还原金氯络合物的电位法研究[D]. 北京. 中国科学院研究生院,2013.
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