Fingerprinting late accretion: Precise measurements of highly siderophile elements in planetary materials

地球地幔中高亲铁元素（HSE、Ir、Rh、Ru、Pd、Pt、Os、Re、Au）的过量丰度和比例通常可以解释为地核和月球形成后大型星子的晚期吸积。最近的分析进展提高了行星材料中某些HSE丰度数据的精度。这些数据暗示，地球的地幔可能具有独特的HSE比例，这与通常被认为是类地行星组成部分的原始陨石不同。撞击融化了40亿年前晚期增生形成的一个大型月球盆地中的岩石，并显示出与地球地幔相似的HSE丰度模式。与地球不同的是，在地球上，早期被陨石污染的地壳通过循环作用重新回到了地幔中，而月球地壳自45亿年前形成以来，仍然保留着形成过程的记录。月球撞击岩是源自撞击的火流星和月球高地地壳的陨石成分的混合物。本研究将借助原始陨石、地幔样品和月球样品中Rh、Au等HSE的精确丰度数据，对地幔和月壳中HSE特征的详细来源进行评价。我们将研究月球地壳不同成分的起源，特别是陨石成分的起源和性质，月球岩浆海洋对月球高地岩石施加的HSE特征以及对早期地球表面过程的影响。

Excess abundances and proportions of the highly siderophile ( iron-loving ) elements (HSE; Ir, Rh, Ru; Pd, Pt, Os, Re, Au) in the Earth s mantle are commonly explained by late accretion of large planetesimals after formation of the Earth s core and the Moon. Recent analytical progress resulted in improved precision of abundance data for some of the HSE in planetary materials. These data hint that the Earth s mantle may be characterized by unique proportions of HSE that are unlike those in primitive meteorites that are commonly assumed to represent the building blocks of the terrestrial planets. Impact melt rocks from one of the large lunar basins formed during late accretion 4 billion years ago, and show HSE abundance patterns similar to those in the Earth s mantle. In contrast to Earth where recycling has returned early meteorite-contaminated crust back into the mantle, the lunar crust still maintains a record of processes since its formation 4.5 billion years ago. Lunar impact rocks are mixtures between meteoritic components derived from the impacting bolides and crust of the lunar highlands. This study will evaluate the detailed origin of the HSE signature in Earth s mantle and the lunar crust with the help of precise abundance data for Rh, Au and other HSE in primitive meteorites, samples of the Earth s mantle and lunar samples. We will study the origin of the different constituents of the lunar crust, in particular the origin and nature of meteoritic components, the HSE signature imposed on lunar highland rocks by the lunar magma ocean and implications for processes on the surface of the early Earth.