CSEDI: Collaborative Research: Experimental Partitioning of Highly Siderophile Elements at Ultratrace Level for Understanding the Conditions of Core Formation

CSEDI：合作研究：超痕量水平的高亲铁元素的实验分配，以了解核心形成的条件

• 批准号: 2001043
• 负责人: Michael Krawczynski
• 金额: $ 13.67万
• 依托单位: Washington University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-05-01 至 2025-04-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2001043&HistoricalAwards=false
• 关键词: CSEDI; Collaborative; Research; Experimental; Partitioning

Gold, platinum, osmium, irridium, ruthenium, rhodium, palladium, and rhenium (known collectively as highly siderophile elements) are among the rarest elements available to mankind. Their widespread use in technology and the arts results in a high cost. It also justifies extensive mining, which has a high environmental and human health impact. The reason for their scarcity is that they were scavenged into the core when Earth separated into a silicate outer layer (mantle and crust) and a metallic core. Even if these elements are highly depleted in the mantle, previous experimental work indicates that they are overabundant relative to expectation for scavenging by the core. Available experiments suggest that the mantle should be completely barren of these elements, which is not what is seen. A likely explanation for this discrepancy between experiments and observations is that the highly siderophile elements were delivered into the Earth's mantle by the late impact addition of meteoritic material after the core had formed. There are differences however between the composition of the mantle and meteorites, notably for ruthenium, and an important question is whether previous experiments reliably predict the scavenging of highly siderophile elements in the core. These experiments were limited in the pressure-temperature conditions that they could achieve and relies on large extrapolations to make inferences about the scavenging efficiency of the core. A new experimental approach relying on the laser ionization of selected highly siderophile elements coupled with experiments done in diamond anvil cells that can routinely reach pressures of 700,000 atmospheres and temperatures of 4500 K, will allow the partitioning of highly siderophile elements to be measured under core formation conditions without relying on large extrapolations. This work will apply a relatively new technique (Resonant Ionization Mass Spectrometry - RIMS) to in situ ultratrace analyses, which can find applications in a variety of fields outside of Earth sciences, including material sciences/development and nuclear forensics. The project is a multidisciplinary collaboration between geochemists, physicists and instrument developers, an experimental petrologist, and a high-pressure mineral physicist. The project will support two graduate as well as undergraduate students, who will be trained on a multidisciplinary research project. The PIs will also be involved in outreach at the K-12 level through the French-American Science Festival.The reason for the depletions in highly siderophile elements (HSEs) in the mantle is their removal into Earth’s core, and their subsequent replenishment by late accretion of extraterrestrial material representing ~0.5 % of Earth’s mass. To first order, this model of late delivery of chondritic material to the Earth can account for the abundance of HSEs in the mantle but it fails to explain the elevated Ru/Pt and Pd/Pt ratios in the mantle relative to chondrites and other HSEs. One explanation for these high ratios is that Ru and Pd may be less siderophile or chalcophile compared to other HSEs, resulting in their partial retention in mantle when the core formed. Testing this hypothesis is however difficult because the relevant metal/silicate partitioning experiments have been done at P-T conditions that are quite remote from those that are thought to have prevailed during core formation. The investigators will study the origin of HSEs in Earth’s mantle by applying a novel ultra-trace element quantification technique known as RIMS to measure the concentrations of selected HSEs in metal-silicate experiments done using piston cylinders and diamond anvil cells (DACs). Through this collaboration between geochemists, physicists and instrument developers, an experimental petrologist, and a high-pressure mineral physicist, the research group will study the effect of nano/micro metal nuggets on metal/silicate partition data, and will measure the partition coefficients of Ru, Pd, and Pt at 0–70 GPa and 2100–4500 K, which spans conditions relevant to core formation.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

黄金，铂，渗水，hod恒，钯和rhenium artest元素可用于人类的广泛使用，而Alts则造成了较高的成本。人类人类人类人类人类人类人类人类人类人类人类人类人类人类人类人类人类H分离为硅酸盐外层（地幔和地壳），即使是在金属元素中也被耗尽。地幔，以前的实验工作过多，因为Xperiments对XPeriments的清除量都表明，在核心的后期核心添加了核心的核心元素中，应将其贫瘠的经验和观测形成的是差异，地幔的组成和陨石的问题是，prepius是否可以预测核心的筛查元素。在精选元件的激光电离上，在钻石铁砧细胞中进行的couth实验通常可以使700,000个大气和4500 K的温度弥补，这将使对核心的分配能够被测量，而无需依靠大型杂交。相对新技术（谐振质谱 - RIMS）可以在各种地球科学中找到应用，包括材料科学/发育和核心前肢。地下学生将接受CT的培训。核心，以及它们的亚分离补充，通过迟到的外星物质的后期积聚，抑制了地球质量的约0.5％。地幔中的PT和PD比相对于Chonedrites和其他HSE，导致其在地幔中的部分保留率是相关的金属/淤积实验。核心形成。调查人员将通过应用弹道元素定量E来测量使用活塞圆柱体和钻石砧（DACS）在Metal-Similicate实验中测量所选HSE的浓度，从而在地球上的HSE起源。在地球化学主义者之间，研究小组将纳米/微型金属块对金属/硅酸盐分区数据PD的影响，而PT为0-70 GPA和2100–2100–4500 K并被认为是值得使用Tounlectul值得更广泛影响的评论标准的值得支持的。