Isotope Fractionations during volatile loss from Planets and Asteroids

已知内太阳系中的岩石天体与CI陨石相比，缺乏中等挥发性的元素，CI陨石是行星和卫星的主要组成部分。这些物体的挥发物含量由富含挥发物的C1-C4材料和挥发物贫乏的材料的混合控制。Norris和Wood（2017）最近的工作表明，硅酸盐地球中的挥发性元素丰度与硅质系统中这些元素的挥发性密切相关，这表明地球的挥发性元素预算可以通过早期地球形成事件期间的蒸发和脱挥发分来解释。这挑战了传统的假设，即这些元素的消耗可以解释为这些元素的核心。如果挥发性是元素贫化的主要原因，我们应该能够通过观察同位素分馏来观察这一过程。我们这个项目的目的是通过调查挥发分对几种元素的同位素组成的影响来测试挥发分假说。我们将研究硅酸盐地球中与CI-硅酸盐材料相比具有不同程度的挥发性和消耗的元素，从Zn和Cd开始，逐渐发展到Cu和Pb。由于地球、火星、灶神星和各种陨石的同位素组成存在差异，因此我们将集中讨论这些问题。我们将在实验室中对掺入微量元素的岩石粉末进行相对较短（60分钟）的高温熔炉实验，以验证我们的假设。样品中掺杂了所研究的元素，以确保我们能够在实验后准确地测量它们。将对产生的运行产品进行元素和同位素丰度分析。通过将实验结果与地球、月球、火星和陨石的现有数据进行比较，我们将能够测试最初提出的脱挥发分模型，并进一步改进描述地球挥发性预算早期演变的模型。该项目是科学和技术设施理事会（STFC）的天文学和空间科学研究的一部分，特别侧重于科学挑战B：“恒星和行星系统如何发展，生命是我们星球所独有的吗？'.该项目将在牛津大学地球科学系B. J.（Bernard）Wood教授和J.（Jane）巴灵博士的监督下进行。[1]加州诺里斯Wood，B. J.（2007年）。地球的挥发性物质通过熔化和蒸发而形成。Nature，第549卷，第507-510页

The rocky bodies in the inner Solar System are known to be depleted in moderately volatile elements compared to CI chondritic meteorites, the main building blocks of the planets and moons. The volatile content of these bodies was governed by the mixing of volatile rich CI chondritic material and a volatile-poor material. Recent work by Norris and Wood (2017) has shown that volatile element abundances in the silicate Earth correlate well with the volatility of those elements in a siliceous system, suggesting that the Earth's volatile element budget may be explained by vaporization and devolatilization during early Earth forming events. This challenges the conventional hypothesis that these element depletions can be explained by incorporation of these elements in the core. If volatility is the main cause of element depletions, we should be able to observe this process by looking at isotope fractionation. Our aim for this project is to test the devolatilization hypothesis by investigating the effects of devolatilization on the isotopic composition of several elements. We will look at elements with varying degrees of volatility and depletion in the silicate Earth compared to CI chondritic material, starting with Zn and Cd and progressing to Cu and Pb. We will focus on these as variations in isotopic composition for these elements are known for the Earth, Mars, Vesta and various meteorite classes.We will test our hypothesis in the lab by performing relatively short (60 minute) experiments in a furnace at high temperature, in a heavily reducing environment at atmospheric pressure on rock powders that have been doped with trace elements. The samples are doped in the studied elements to ensure we are able to measure them accurately after the experiments. The resulting run products will be analysed for both elemental and isotopic abundances. By comparing the results from the experiments with available data for the Earth, Moon, Mars and meteorites we will be able to test the initially proposed model of devolatilization and further advance models describing the early evolution of the Earth's volatile budget. This project is a part of the Science and Technology Facilities Council (STFC)'s Astronomy and Space Science Research, specifically focused within Science Challenge B: 'How do stars and planetary systems develop and is life unique to our planet?'. This project will be performed under the supervision of Professor B.J. (Bernard) Wood and Dr. J. (Jane) Barling from the Department of Earth Sciences at the University of Oxford.[1] Norris, C.A., Wood, B.J. (2007). Earth's volatile contents established by melting and vaporization. Nature, vol. 549, p. 507-510