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

地球有一个金属核心和一个单独的硅酸盐地幔。它们在地球历史上很早就相互分离了。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，因为分离的足迹显示在地幔中应主要加入核心的元素的剩余丰度中。目前尚不清楚地核和地幔之间的相互作用是持续分离、静态稳定状态还是反应性回流。该项目的目的也是了解核-地幔相互作用的状态和机制。许多项目活动的重点是分析岩石中亲铁(接芯)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部羽流上升有关。如果来自地核的物质被并入深部的羽流中，Os的同位素组成可能反映了放射性铂和Re产生的放射性成因Os。与地幔相比，铂和稀土在地核中富集，并衰变为Os的特定同位素，提供了识别这种相互作用的特征。为了充分评估已证实的任何此类信号，有必要了解这些亲铁物质在核和地幔系统中的地球化学行为。实验室的实验研究是针对高温高压下的这种行为进行的。贵金属微金块作为Os和其他铂族元素的物理寄主，给实验室实验和分析带来了技术问题，也可能给解释天然岩石化学带来了技术问题。研究人员开发了一种技术，利用Os的同位素组成和丰度来推断Os的行为，去掉了金块效应。他们建议将这项技术扩展到铂，这是另一个在理解核-地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.