| 黄铁矿形貌特征高温高压实验研究 |
| 高凤
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| 导师 | 李和平
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| 2014
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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 | 黄铁矿
形貌特征
高压釜
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| 摘要 | 黄铁矿是地壳中分布最广的硫化物矿物，常以立方体、八面体和五角十二面体等形态产出。研究表明，特定形貌黄铁矿在形成温度、压力、pH、Eh、氧逸度和硫逸度等方面差异明显，因此，黄铁矿的形貌特征可以提供丰富的地质信息。目前，国内外黄铁矿形貌研究主要采用常规的野外采样分析法和高温高压实验模拟两种方法。在常规的野外研究中，金矿床中黄铁矿的形貌研究程度比较高；室内高温高压实验研究主要通过水热合成法、化学气相沉积法和化学溶解再结晶法合成黄铁矿并观察黄铁矿的生长习性，因研究方法的不同和实验技术条件的限制，目前对黄铁矿形貌特征的认识尚不能统一与完善，还没有一个统一的结论供大家在实际生产中使用。本论文以高温高压水热合成法和化学溶解再结晶法为实验手段，开展研究控制黄铁矿形貌特征因素的实验，以本课题组自行研制的腐蚀电化学多功能高压釜系统为实验平台取得了以下认识： (1) 以黄铁矿-H2O/NaCl溶液体系为研究对象，反应温度设为400℃和450℃，压力从12-49 MPa不等，起始黄铁矿粒径小于200目。反应结束后样品的成分仍为黄铁矿，样品形貌与反应前相差无几，仍是棱角分明，未见重结晶的黄铁矿颗粒以及增生环带，表明成分简单的反应溶液不利于黄铁矿的重结晶和增生环带的形成，可能还需要其他元素的掺杂以降低反应的自由能。 (2) 400℃、26MPa的条件下以FeSO4+Na2S2O3+H2O体系为研究对象，实验产物为黄铁矿，其形貌主要表现为草莓状、立方体和其他形貌的聚形晶。 (3) 以FeSO4+Na2S2O3+S+H2O体系为研究对象，实验温度由250℃开始每50℃为一个实验点逐渐增加到450℃，填充度不变，压力随着温度的升高而升高，实验产物为黄铁矿，其形貌受温度、压力、浓度、反应时间控制，反应产物主要形貌有立方体、草莓状、八面体、立方体和八面体结合体、立方体和五角十二面体的结合体、层状和柱状等。温度高于等于400℃时，有利于立方体黄铁矿的形成，温度低于400℃有利于八面体、五角十二面体和更复杂晶形的黄铁矿的形成；温度高于400℃时，反应物浓度越低越有利于完整的立方体黄铁矿生成；其他条件相同的条件下，反应物浓度高或者反应时间短的实验更有利于形成晶形复杂的晶体。 |
| 其他摘要 | Pyrite is the most wide-spreading and abundant sulfide in the crust. The occurrence of pyrite is characterized as cube, octahedron or pyritohedron, presenting particular typomorphic features. Particular geological information and implication can be interpreted from the typomorphic feature of pyrite, because it records the original temperature, pressure, pH, Eh, fugacity of O2 and S during mineralization. There are two basic research methods of this interpretation: analysis of field sample and experimental simulation of high temperature and pressure. The former one is more frequently applied for the pyrite in goldmine study while the later one is focusing on the growth habit of synthesis pyrite. Due to the variation of research methods and limitation of technique, it fails to come to a systematic and complete conclusion on typomorphic features of pyrite for workers to utilize in practice. The paper employs hydrothermal synthesis and chemical dissolution-recrystallization method at high temperature and high pressure on the corrosion electrochemistry constructing a multi-function autoclave system as the experiment platform to study the controlling factors of pyrite morphology. The conclusion we reached are as follows: (1) The experiment under the condition of 400 ℃ or 450 ℃、12-49 MPa using pyrite+H2O±NaCl system as the research object, the initial pyrite particle is less than 200 meshes. After the reaction, the sample composition with the same sharp morphology as the initial pyrite, and no new pyrite and growth bands been found. The missing of recrystallization of pyrite particles and growth bands indicate that the recrystallization normally fail to be well developed in a solution with simple compositions, rendering the possibility and necessity of mixing of other elements in the fluid to decease the free energy. (2) Under the framework of 400 ℃, 26 MPa for FeSO4+Na2S2O3 +H2O system as the research object, the experimental product tends to be pyrite with the mainly morphology of strawberry, cube and other morphology of polycrystal. (3) Using the FeSO4+Na2S2O3+S+H2O system as the research object, The experiment temperature increases from 250℃ to 450℃, with a gradient of 50℃ and constant filling degree, and the pressure will come along with the increase of temperature, the experimental product is pyrite with the mainly morphology of cube、strawberry、octahedron、cube and octahedron multiple form、 cube and pyritohedron multiple form、layered、columnar and so on. Cubic pyrite is formed at a higher T(400℃), while the octahedron、pyritohedron and other complex form pyrite are formed at a lower T(under 400℃); when temperature is higher than 400℃ , the complete cubic pyrite is formed at a lower reactant concentration; when other conditions are the same, the complex morphology pyrite is formed at a higher reactant concentration or short reaction time. |
| 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/352002/5904
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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 |
高凤. 黄铁矿形貌特征高温高压实验研究[D]. 北京. 中国科学院研究生院,2014.
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