文献类型：期刊文献

中文题名：紫硫镍矿交代镍黄铁矿的水热反应机理及动力学

英文题名：Kinetics and Mechanism of Hydrothermal Alteration from Pentlandite to Violarite

作者：夏方[1];陈国荣[2];Allan PRING[3];Joёl BRUGGER[3];Yung NGOTHAI[1];Brain O'NEILL[1];Chris COLBY[1];Christophe TENAILLEAU[3];王海鹏[4];杨云霞[2]

机构：[1]School of Chemical Engineering,University of Adelaide,Adelaide,SA 5005,Australia;[2]华东理工大学材料科学与工程学院,超细粉末教育部重点实验室,上海200237;[3]Department of Mineralogy,South Australian Museum,North Terrace,Adelaide,SA 5000,Australia;[4]BHP Billiton Innovation,1/18 Vale Street,Birmingham Gardens,NSW 2287,Australia

年份：2007

卷号：81

期号：10

起止页码：1378

中文期刊名：地质学报

外文期刊名：Acta Geologica Sinica

收录：CSTPCD;;Scopus;北大核心:【北大核心2004】；CSCD:【CSCD2011_2012】；

基金：澳大利亚政府ARC项目(编号DP0772229)资助的成果

语种：中文

中文关键词：水热反应;交代作用;动力学;镍黄铁矿;紫硫镍矿;磁黄铁矿

外文关键词：hydrothermal reaction ; replacement reaction ; kinetics ; pentlandite; violarite; pyrrhotite

摘要：本工作首次在实验室条件下对浅生区紫硫镍矿(Ni,Fe)3S4交代镍黄铁矿(Ni,Fe)9S8水热反应的机理及动力学进行了研究。起始反应矿物采用高纯自然镍黄铁矿,合成纯镍黄铁矿或合成镍黄铁矿-磁黄铁矿集合体。反应pH值采用0.2M醋酸-醋酸纳缓冲溶液控制在3～5的范围内。反应进程由X-射线衍射物相定量分析及扫描电镜观察进行跟踪。结果表明,当反应温度恒定在80℃时,交代20(4)%的镍黄铁矿需792h。相同条件下加入少量H2S可将反应速率提高一倍。当反应在125℃饱和蒸汽压水热环境下进行时,完全交代纯镍黄铁矿需约168h。此过程由于磁黄铁矿的存在而被催化,交代集合体中的镍黄铁矿仅需68h,进一步反应磁黄铁矿被交代成白铁矿。磁黄铁矿的催化作用可能源于溶解产生的微裂纹加速了流体的传质过程。当反应温度升高至145℃时,速率反而下降,不遵循Arrhenius经验规律。动力学分析得80℃速率常数介于5.8×10-8～3.0×10-7/s之间,125℃及145℃速率常数分别介于2.8×10-6～2.08×10-5/s及1×10-6～5.1×10-6/s之间,远高于同温度下固相扩散反应的速率常数,表明该反应在地质时标上为一快速反应。此外,用背散射电子显微技术对矿物表面形貌进行了分析,发现交代产物紫硫镍矿具有颗粒细小及存在微裂纹等特征,与自然界浅生矿床中的紫硫镍矿非常相似;电镜实验还表明该交代作用是一个典型的耦合溶解-再沉淀反应。其耦合机制的驱动力可能与反应界面处微空隙对流体饱和度的控制有关。
The kinetics and mechanism of the hydrothermal alteration from pentlandite （Ni, Fe）9 88 to violarite （Ni, Fe）3S4 has been studied by a series of experiments. High purity natural pentlandite, synthetic pure pentlandite or synthetic pentlandite/pyrrhotite assemblages were utilized as the starting minerals. The minerals were reacted with a 0.2 M acetic acid/sodium acetate buffer （pH 3-5） at temperatures ranging from 80℃ to 145℃. The reaction progresses were monitored by Rietveld quantitative phase analysis based on X-ray diffraction data. At 80℃, the reaction took 792 h to transform 20（4）% pentlandite to violarite. This rate was improved by adding small amount of hydrogen sulfide gas into the buffer, as 40 （4）% pentlandite was altered after an identical time. At 125℃, the reaction took 168 h to reach completion for pure pentlandite. This process was catalyzed by pyrrhotite as the reaction time was reduced to 68 h for pentlandite in pentlandite/pyrrhotite assemblage, with marcasite produced after further soaking. The catalytic role of pyrrhotite is probably due to its dissolution, which provides large surface area as well as cracks for easier mass transfer. The classic Arrhenius rule does not apply to the kinetics as the reaction rate slowed down when increase the temperature from 125℃ to 145℃. The rate constants derived from Avrami equation range from 5.8×10^-8/s to 3.0×10^- 7/s for reactions at 80℃, 2.8×10^-6/s to 2.08×10^-5/s for 125℃, and 1×10^-6/s to 5.1×10^-6/s for 145℃. These rate constants are far excess those for solid-state diffusion controlled reactions, and indicate a rapid reaction on the geological time scale. Textual evolutions during the reaction were monitored by observing backscattered images of cross-sections of minerals prior to and after reactions. Fine-grained violarite crystals with micro-crack feature have been observed, indicating a coupled dissolution-reprecipitation mechanism rather than a solid state diffusion controlled mechanism. This mechanism is probably driven by the reaction front which controls the saturation state of the fluid.