Environmental mobility of tin

锡的环境迁移性将通过以下方法进行评估：1)热力学测量和建模；2)野外环境中原生硫化锡风化的化学和结构研究；3)原生硫化锡和次生氧化物质之间锡的同位素变化。热力学测量将包括溶液量热法（生成焓）和弛豫量热法（熵）对一组锡的schoenfliessite基团，□2(BSn)(OH)6，其中B = Ca, Fe2+, Mg, Mn2+, Zn， Cu和Fe3+。这些数据将用于计算这些矿物质在不同pH值下的溶解度，并评价矿井排水中这些矿物质的饱和状态。风化硫化锡将在选定的现场（历史矿山）收集，并通过偏振光显微镜、电子探针、微x射线衍射或透射电子显微镜进行研究，以确定次生锡矿物的性质。有限的初步工作表明，它们可能接近舍恩氟site族的锡氢氧化物。还将分析伴生原生矿物（如黄铁矿、毒砂）的风化产物的锡含量，以评估历史矿区的锡流动性。锡在原生硫化物和次生氧化矿物之间的同位素变化有可能指示锡在其中移动和丢失的地球化学过程。两个储层之间的同位素差异将表明锡的流动性，即使矿物学调查没有单独捕获。这项工作的目的是预测锡在采矿现场的流动性，在其他金属元素（铁，铜，锌）的存在下，这些元素能够形成氢氧化锡矿物。

Environmental mobility of tin will be evaluated by the means of i) thermodynamic measurements and modeling, ii) chemical and structural investigation on weathering of primary tin sulfides in field settings, and iii) isotopic variations of Sn between primary sulfides and secondary oxidic materials. The thermodynamic measurements will consist of solution calorimetry (with resulting enthalpies of formation) and relaxation calorimetry (entropies) on a suite of tin hydroxides of the schoenfliesite group, □2(BSn)(OH)6, with B = Ca, Fe2+, Mg, Mn2+, Zn, Cu, and Fe3+. The data will be used to calculate solubility of these minerals under variable pH and to evaluate the saturation state of mine drainage waters with respect to these minerals. Weathered tin sulfides will be collected at selected field sites (historical mines) and investigated by polarized light microscopy, electron microprobe, micro-X-ray diffraction or transmission electron microscopy, in order to determine the nature of the secondary tin minerals. Limited preliminary work suggests that they may be close to the tin hydroxides of the schoenfliesite group. Weathering products of the associated primary minerals (e.g., pyrite, arsenopyrite) will be also analyzed for their Sn content, in order to evaluate tin mobility at the historical mining sites. Isotopic variations in Sn between the primary sulfides and secondary oxidic minerals have the potential to indicate geochemical processes in which tin is mobile and lost. Isotopic differences between the two reservoirs would indicate mobility of tin, even if not captured by the mineralogical investigation alone. The aim of this work is to predict mobility of tin at mining sites, in the presence of other metallic elements (Fe, Cu, Zn) which are able to form tin hydroxide minerals.