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

行星材料中 176-镥衰变常数的测定及其对地球内部 Lu-Hf 演化的影响

• 批准号: 1119135
• 负责人: Audrey Bouvier
• 金额: $ 14.34万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-10-01 至 2014-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1119135&HistoricalAwards=false
• 关键词: Determination; 176; lutetium; Decay; Constant

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.

地球是如何形成的，其最初的组成是什么？176Lu-176Hf系统作为行星演化的计时器和示踪剂在地球化学中得到了广泛的应用，但地球形成的初始条件仍然不清楚。一些陨石是行星形成早期(约45.7亿年前)仅存的见证者。这项拟议研究的目的是测量一些已知年龄的最原始的陨石天体的Lu-Hf同位素组成。这项拟议的工作将严格限制岩石行星建筑材料的176Lu衰变常数和初始Hf同位素组成。这些参数不仅对地球化学界解释Hf非常重要，而且对Hadean(38亿多年前)和太古宙(2.5~38亿年前)岩石的Nd3+同位素记录也是非常重要的。重要的是要了解地球如何在其历史上形成和演化的过程，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的行星。这项研究将使用最先进的质谱学技术，与法国克莱蒙费朗大学的Maud Boyer博士小组合作，测量Lu-Hf同位素组成以及其他行星演化感兴趣的元素的同位素组成。该项目将对Lu-Hf，以及Sm-ND，同位素地球化学研究和了解地球和其他类地行星上地幔和地壳形成的过程和时间具有重大意义。它还将为矿物物理、地球物理、行星科学和天体物理等其他研究领域做出贡献。