Determination of the 176-lutetium Decay Constant in Planetary Materials and Implications for the Lu-Hf Evolution of the Interior of the Earth

地球是如何形成的，它的镥铪放射性同位素系统的初始成分是什么？176Lu-176Hf系在地球化学中被广泛用作行星演化的计时器和示踪剂，但地球形成的初始条件尚不清楚。一些陨石是行星形成最早阶段（约45.7亿年前）的唯一见证人。提出的研究目的是测量一些已知年龄的最原始陨石的Lu-Hf同位素组成。所提出的工作将严格限制176Lu衰变常数和岩石行星建筑材料的初始Hf同位素组成。这些参数对地球化学界解释冥古宙（超过38亿年）和太古宙（25 - 38亿年）岩石的铪和钕同位素记录非常重要。重要的是要了解地球在其历史中如何形成和演化的过程，因为它影响了地球如何以及何时成为太阳系中的一颗活跃行星。这项研究将与法国克莱蒙费朗大学（University of Clermont-Ferrand）的Maud Boyet博士团队合作，使用最先进的质谱技术来测量Lu-Hf同位素组成以及其他对行星演化感兴趣的元素的同位素组成。该项目将对Lu-Hf、Sm-Nd、同位素地球化学研究以及对地球和其他类地行星上地幔和地壳形成过程和时间的理解产生重大影响。它还将对矿物物理学、地球物理学、行星科学和天体物理学等其他领域的研究作出贡献。

How did the Earth form and what was its initial composition for the lutetium-hafnium radiogenic isotopic system? The 176Lu-176Hf system is widely used in geochemistry as a chronometer and tracer of planetary evolution but the initial conditions for the formation of the Earth remain unclear. Some meteorites are the only witnesses left of the earliest stages of planetary formation (~4.57 billion years ago). The objective of the proposed research is to measure the Lu-Hf isotopic composition of some of the most pristine meteoritic objects of known ages. The proposed work will place tight constraints on the 176Lu decay constant and initial Hf isotopic composition of the building materials of rocky planets. These parameters are extremely important to the geochemical community in the interpretation of the hafnium but also the neodymium isotopic records of Hadean (more than 3.8 billion years old) and Archean (2.5 to 3.8 billion years old) rocks. It is important to understand the processes responsible for how Earth formed and evolved through its history as it influenced how and when the Earth became an active planet in the Solar System. This study will be performed using state-of-the-art mass spectrometric techniques for measuring the Lu-Hf isotopic composition and also the isotopic compositions of other elements of interest for planetary evolution in collaboration with Dr. Maud Boyet's group at the University of Clermont-Ferrand (France). This project will have major implications for the Lu-Hf, and also Sm-Nd, isotopic geochemical studies and understanding the processes and timing for mantle and crust formation on the Earth and other terrestrial planets. It also will make contributions to other fields of research such as mineral physics, geophysics, planetary sciences, and astrophysics.