Collaborative Research: CSEDI--Origin and Evolution of Highly Siderophile Elements in Earth's Mantle

地球有一个金属核和一个单独的硅酸盐地幔。它们在地球历史的早期就彼此分离了。这种分离是地球最基本的化学差异。该项目的目标是更多地了解分离过程的时间和地球化学细节，因为分离的足迹出现在地幔中主要加入地核的元素的剩余丰度中。目前还不清楚地核和地幔的相互作用是否在持续分离，静态稳定状态或反应性回流的意义上进行。了解核幔相互作用的状态和机制也是本项目的目的。项目活动的大部分侧重于分析岩石中亲铁（核连接）元素Os的同位素组成和丰度，这些岩石被认为与核幔边界的深羽上升有关。如果来自地核的物质被纳入深羽流，则Os的同位素组成可能反映了放射性Pt和Re产生放射性Os。Pt和Re在地核中相对于地幔富集，并衰变为特定的Os同位素，这提供了识别这种相互作用的特征。为了全面评价这些已证实的信号，有必要了解这些亲铁物质在地核和地幔系统中的地球化学行为。实验室研究是针对这种行为在高压和高温。实验室实验及其分析的技术问题，并可能也解释天然岩石化学，贵金属微块的出现作为物理主机的Os和其他Pt族元素。研究人员已经开发出一种技术，利用同位素组成和丰度的Os来推断行为的Os，剥离块金效应。他们建议将这种技术扩展到Pt，这是另一种在理解核幔系统中至关重要的亲铁元素。

The Earth has a metallic core and a separate silicate mantle. They separated from one another very early in Earth's history. This separation is the most fundamental chemical differentiation of the planet. The objective of this project is to learn more about the timing and geochemical details of the separation process(es) because the footprint of the separation appears in the residual abundances in the mantle of elements that should have predominantly joined the core. It is unclear whether the interaction of the core and mantle is ongoing in the sense of a continuing separation, a static steady state, or a reactive regurgitation. It is also the purpose of this project to learn about the state and mechanisms of core-mantle interaction. Much of the project activities are focused on the analysis of the isotopic composition and abundance of siderophile (core joining) element Os in rocks thought to be related to the rise of deep plumes from the core-mantle boundary. If material from the core is incorporated in deep plumes, the isotopic composition of Os may reflect the production of radiogenic Os from radioactive Pt and Re. Pt and Re are enriched in the core compared to the mantle and decay to specific isotopes of Os providing a signature to recognize such interactions. In order to fully evaluate any such signals confirmed, it is necessary to know the geochemical behavior of these siderophile materials across core and mantle systems. Experimental laboratory investigations are directed towards this behavior at high pressure and temperature. Technical problems for laboratory experiments and their analysis, and possibly also for interpreting natural rock chemistry, are presented by the occurrence of noble metal micro-nuggets as the physical host to Os and other Pt-group elements. The investigators have developed a technique using both the isotopic composition and abundance of Os to infer the behavior of Os, stripped of the nugget effect. They propose to extend this technique to Pt, another siderophile element of key importance in understanding the core-mantle system.