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: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=709637
• 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.

高度亲铁的元素(HSE)包括更常见的贵金属(铂、钯、铑和金)以及稀有品种(Re、Os、Ru和Ir)。它们都对社会有用，因为它们具有特殊的热、表面和电子性质。HSE对地质学家来说也很有价值，因为它们独特之处在于它们不会吸氧，并与铁、硫以及其他类似硫的元素结合在一起，如砷。因此，HSE对行星如何分离成金属核心、地幔和地壳非常敏感。我的研究计划对这些过程进行了实验室模拟，重点是确定HSE是如何在正常背景水平上浓缩的；无论是通过铁金属、其他矿物还是不寻常的铁-硫(硫化物)熔体。计划中的研究将继续工作，以了解硫化物熔融从岩浆中提取HSE的效率，并调查砷的作用。砷是一种元素，通常在地球上稀有，但在岩浆消化沉积岩时集中。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以及相关的亲硫(或亲硫)元素方面的作用。对硫化物熔体清除能力的了解，使得通过测量其他行星表面熔岩的HSE含量变得更容易，因为这些熔岩的硫化物一直留在深处。这对于了解月球的起源尤为重要，因为月球内部的样本无法获得，因为矛盾的是，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水平似乎太低了。在一些矿床中，发现砷矿物中含有较高浓度的更有价值的HSe(铂、Rh)，因此确定它们的形成方式和时间将有助于评估砷作为贵金属的“主要收集剂”。关于加压水在溶解HSE和“类硫”元素方面的作用的信息被用来确定当洋底向下推到毗邻的构造板块之下时产生的流体在多大程度上将这些元素向上带入形成火山和矿藏的熔融带。然后还可以预测残留的脱水物质的成分，这有助于洞察地球深处的长期成分变化，以及当这种物质在深处熔化时带回地表的异常元素浓度的来源。总而言之，这项工作旨在为使用HSE和相关元素了解行星的形成和演化提供必要的信息。从这项研究中获得的信息对勘探和采矿业也很有价值，因为它提供了洞察这些要素如何集中到经济层面的机制。