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: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=646211
• 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.

高亲铁性或亲铁性元素（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）。它们都对社会有用，因为它们具有特殊的热、表面和电子特性。HSE对地质学家来说也很有价值，因为它们的独特之处在于它们倾向于避免氧气，并与铁、硫以及其他“类硫”元素（如砷）结合。因此，HSE对行星如何分离成金属核、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，特别关注于确定HSE如何集中在正常背景水平之上；它可能是由铁金属、其他矿物或不寻常的铁硫（硫化物）熔体形成的。计划中的研究将继续致力于了解硫化物熔体从岩浆中提取HSE的效率，并研究砷的作用，砷是一种在地球上通常稀缺的元素，但在岩浆消化沉积岩时富集。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（或亲铜）元素方面的作用。了解硫化物熔体的清除能力，可以更容易地通过测量表面熔岩来盘点其他行星的HSE含量，这些熔岩的硫化物仍留在深处。这对于了解月球的起源尤其重要，因为月球内部样本是不可获得的，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，发现含有高浓度更有价值的HSE （Pt, Rh）的砷矿物，因此确定它们如何以及何时形成将有助于评估砷作为贵金属的“主要收集器”。关于加压水在溶解HSE和“类硫”元素中的作用的信息用于确定当海底向下冲至相邻构造板块下方时所产生的流体的程度，这些流体将这些元素向上携带到熔化区，从而产生火山和矿床。残留的脱水物质的成分也可以被预测，这为深入了解地球深处的长期成分变化提供了见解，以及当这些物质在深处融化时带回地表的不寻常元素浓度的来源。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资料对勘探和采矿工业也有价值，因为它提供了对这些要素如何集中到经济水平的机制的见解。