VulcansFluids:The behaviour of halogens and sulphur in natural high temperature processes

氯、氟和硫是火山喷出的气体和高温富水流体的重要组成部分，这些流体是许多具有重要经济意义的金属的迁移和沉积的原因。因此，该项目的目的是研究火山熔体中氯、氟和硫的行为，从而确定这些元素在脱气和成矿过程中释放到环境中的条件。这些结果可以应用于地球、火星和其他原行星和小行星上发生的过程。在一个实验中，我们使用硅酸盐、银金属、银和银银（或银银）的混合物来确定Cl 2（或F2）在高温高压下的分压（逸度）。在实验期间，金属和银卤化物化合物形成2种不混溶的液体，控制硅酸盐熔体的Cl（或F）含量。类似的方法用于使用银/银硫化物或铂/铂硫化物混合物（在固定的氧逸度下）在高温和高压下固定S2逸度。实验结束后，硅酸盐（现在是一种玻璃）通过微束方法进行分析，以确定有关元素Cl，F和S的确切含量。第二种新的实验方法使用熔炉，在该熔炉中熔融硅酸盐样品在高温下搅拌，以测定Cl、F、S和痕量金属的相对挥发度。我们的研究结果将整合与众多可用的数据Cl，S和F的流体熔体分配，以确定这些元素在盐水和低密度流体的逸度，因此它们的金属运输能力。 众所周知，地球、月球、火星和灶神星的Cl/F和Cl/S比值之间存在很大差异，所有这些天体都经历了广泛的熔化和挥发损失。我们的研究结果将使我们能够估计在行星和小行星形成过程中发生挥发性损失的不同条件。氯和硫是火山流体中金属氯化物迁移和斑岩铜矿中金属硫化物沉淀的主要介质。我们的研究结果将使我们能够确定潜在的火山网站的经济金属矿床的基础上演变过程中演变的流体和气体的成分。

Chlorine, fluorine and sulphur are important components of the gases emitted by volcanoes and of the high temperature water-rich fluids responsible for transport and deposition of many economically important metals. The aims of this project are therefore to characterise fully the behaviour of chlorine, fluorine and sulphur in volcanic melts and thereby to determine the conditions under which these elements are released to the environment during degassing and ore-forming processes. The results have applications to processes occurring on Earth, Mars and other protoplanetary and asteroidal bodies The project uses two novel experimental approaches. In one we fix the partial pressure (fugacity) of Cl2 (or F2) at high temperatures and pressures using mixtures of silicate, silver metal, silver iodide and silver chloride (or silver fluoride). During the experiment the metal and silver halide compounds form 2 immiscible liquids controlling the Cl (or F) content of the silicate melt. A similar approach is used to fix S2 fugacity at high temperature and pressure using silver/silver sulphide or platinum/platinum sulphide mixtures (at fixed oxygen fugacity). After the experiment the silicate (which is now a glass) is analysed by microbeam methods to determine the exact contents of the element(s) of concern, Cl, F and S. The second novel experimental method uses a furnace in which the molten silicate sample is stirred at high temperature in order to determine relative volatilities of Cl, F, S and trace metals. Our results will be integrated with the numerous available data on fluid-melt partitioning of Cl, S and F to determine the fugacities of these elements in brines and lower density fluids and hence their metal-transport capacities. It is known that there are large differences between the Cl/F and Cl/S ratios of the Earth, Moon, Mars and Vesta, all bodies which have undergone extensive melting and volatile loss. Our results will enable us to estimate the different conditions under which volatile loss occurred during formation of planets and asteroids. Chlorine and sulphur are principal agents in the transport of metals as chlorides in volcanic fluids and in the precipitation of metal sulfides in porphyry copper deposits. Our results will enable us to identify potential volcanic sites of economic metal deposits based on the compositions of fluids and gases evolved during their evolution.