Thermodynamics of selected hydrothermal minerals of As and Sb

在这里，我们建议在贫硫化物流体中合成或获取、表征和测量参与水热过程的精选As和Sb矿物的热力学性质，其温度最高可达400℃。所选矿物包括Co-Ni-Fe三砷化物，斯科特族[(Co，Ni，Fe)As3-x]，与世界各地许多赋存状态的Ni-Co-Fe-Bi矿的形成有关。所选的Sb矿物包括方铅矿(FeSb2O4)和辉石(Sb3+Fe3+2(SiO4)2(OH))，这两种Sb矿物可能形成于缺硫流体。感兴趣的相将在真空硅管中合成或从天然样品中获得。所有样品都将采用各种矿物学技术进行表征。本提案中的主要方法将是高温氧化物熔融量热法。将进行大量检查，以确保收集的数据具有足够的精确度和精确度，可用于热力学建模。用弛豫量热法和差示扫描量热法分别测量了它们的熵和高温热容。这些数据将与现有的水溶液离子状态方程(在热力学软件包，如SUPCRT中实现)结合，并将计算相图。计算的溶解度及其随温度的变化将大大有助于理解热液成矿作用，特别是在贫硫化物流体中。

Here, we propose synthesis or acquisition, characterization, and measurement of thermodynamic properties of selected As and Sb minerals which participate in hydrothermal processes, under temperatures up to 400 ºC, in fluids poor in sulfide. The selected As minerals include the Co-Ni-Fe triarsenides, the skutterudite group [(Co,Ni,Fe)As3-x], relevant to the formation of the Ni-Co-Fe-Bi ores at many occurrences around the world. The selected Sb minerals include schafarzikite (FeSb2O4) and chapmanite (Sb3+Fe3+2(SiO4)2(OH)), two minerals of antimony that may form from sulfur-deficient fluids. The phases of interest will be synthesized in evacuated silica tubes or acquired from natural samples. All samples will characterized by a variety of mineralogical techniques. The principal method in this proposal will be high-temperature oxide-melt calorimetry. A number of checks will be performed to ensure that the collected data are of sufficient accuracy and precision for thermodynamic modeling. Entropies and high-temperature heat capacities will be measured by relaxation and differential scanning calorimetry, respectively. The data will be combined with the existing equations of state for aqueous ions (implemented in thermodynamic software packages, e.g., SUPCRT) and phase diagrams will be calculated. Calculated solubilities and their changes with temperatures will significantly aid in the understanding of hydrothermal ore formation, especially in sulfide-poor fluids.