Deciphering the behaviour of chalcophile and siderophile elements during planetary differentiation

解读行星分化过程中亲铜元素和亲铁元素的行为

• 批准号: RGPIN-2016-05304
• 负责人: Brenan, James
• 金额: $ 2.91万
• 依托单位: Dalhousie University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=615614
• 关键词: Deciphering; behaviour; chalcophile; siderophile; elements

The highly siderophile, or iron-loving, elements (HSE) include the more familiar precious metals (platinum, palladium, rhodium and gold) as well as exotic varieties (rhenium, osmium, ruthenium and iridium). They are all useful to society, owing to exceptional thermal, surface and electronic properties. The HSE are also of value to geologists, as they are unique in their tendency to avoid oxygen, and bond to iron, sulfur, as well as other “sulfur-like” elements, such as arsenic. The HSE are therefore sensitive to how planets separate into a metallic core, mantle and crust. My research program has involved laboratory simulation of these processes, with a specific focus on determining how the HSE get concentrated above normal background levels; be it by iron metal, other minerals, or unusual iron-sulfur (sulfide) melts. The planned research will continue work to understand the efficiency of HSE extraction from magma by sulfide melt, and also investigate the role of arsenic, an element normally scarce in the earth, but concentrated when magmas digest sedimentary rock. Research will also move into a poorly known area, and that is the role of highly pressurized water, containing dissolved solvents, at transporting the HSE, as well as the related sulfur-loving (or chalcophile) elements. Knowledge of the scavenging capacity of sulfide melts makes it easier to inventory the HSE content of other planets from measurements of their surface lavas, whose sulfide has remained at depth. This is particularly important for understanding the origin of the moon, for which interior samples are unavailable, as paradoxically, the HSE levels in lunar lavas seems to be too low if it experienced the same formation history as the earth. In some ore deposits, arsenic minerals containing high concentrations of the more valuable HSE (Pt, Rh) are found, so determining how and when they form will help to evaluate arsenic as a “primary collector” of the precious metals. Information on the role of pressurized water in dissolving the HSE and “sulfur-like” elements is used to determine the extent to which fluids produced when the ocean floor is downthrust beneath adjoining tectonic plates carry these elements upwards, into the zone of melting that gives rise to volcanoes and mineral deposits. The composition of the residual, dewatered material can then be predicted as well, which provides insight into the longterm compositional changes of the deep earth, as well as the origin of unusual element concentrations brought back to the surface when this material is melted at depth. In sum, this work seeks to provide the essential information for using the HSE and related elements to understand how planets form and evolve. Information gained from this research is also of value to the exploration and mining industry, as it provides insight into how the mechanisms by which these elements may be concentrated to economic levels.

高度亲铁元素（HSE）包括更常见的贵金属（铂、钯、铑和金）以及外来品种（铼、锇、钌和铱）。由于具有卓越的热性能、表面性能和电子性能，它们对社会都有用。 HSE 对地质学家也很有价值，因为它们具有独特的避开氧气的倾向，并与铁、硫以及其他“类硫”元素（例如砷）结合。因此，HSE 对行星如何分离成金属核心、地幔和地壳非常敏感。我的研究项目涉及这些过程的实验室模拟，特别关注确定 HSE 如何集中到正常背景水平之上；可能是由铁金属、其他矿物或不寻常的铁硫（硫化物）熔体产生的。计划中的研究将继续致力于了解通过硫化物熔化从岩浆中提取 HSE 的效率，并研究砷的作用，砷是地球上通常稀缺的元素，但在岩浆消化沉积岩时会浓缩。研究还将进入一个鲜为人知的领域，即含有溶解溶剂的高压水在运输 HSE 以及相关的喜硫（或亲铜）元素方面的作用。了解硫化物熔体的清除能力，可以更轻松地通过测量其他行星表面熔岩的含量来清查其 HSE 含量，这些行星的硫化物仍保留在深处。这对于了解月球的起源尤其重要，因为月球内部样本无法获得，但矛盾的是，如果月球熔岩经历了与地球相同的形成历史，那么月球熔岩中的 HSE 水平似乎太低。在一些矿床中，发现了含有高浓度更有价值的 HSE（Pt、Rh）的砷矿物，因此确定它们形成的方式和时间将有助于评估砷作为贵金属“主要捕收剂”的作用。有关加压水在溶解 HSE 和“类硫”元素中的作用的信息可用于确定当海底向下冲到相邻构造板块下方时产生的流体将这些元素向上携带到产生火山和矿藏的熔化区域的程度。然后，还可以预测残留脱水材料的成分，从而深入了解地球深处的长期成分变化，以及当该材料在深处熔化时带回地表的异常元素浓度的来源。总之，这项工作旨在提供使用 HSE 和相关元素来了解行星如何形成和演化的基本信息。从这项研究中获得的信息对于勘探和采矿业也很有价值，因为它提供了有关这些要素如何集中到经济水平的机制的见解。