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Collaborative Research: The Zirconium Isotope Composition and Variability of the Silicate Earth -- A Pilot Study

合作研究：硅酸盐地球的锆同位素组成和变化——一项试点研究

基本信息

批准号：
1823748
负责人：
Mauricio Ibanez-Mejia
金额：
$ 30.95万
依托单位：
University of Rochester
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
2018
资助国家：
美国
起止时间：
2018-09-01 至 2021-06-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1823748&HistoricalAwards=false
关键词：
Collaborative Research Zirconium Isotope Composition

项目摘要

Over the past 60 years the element zirconium (Zr) has been increasingly used as a tool for deciphering the differentiation history of the Earth and other 'rocky' planetary bodies in our Solar System. Despite being a 'trace element' (i.e., element of relatively low concentration) in most geological environments, its preferential enrichment in the chemically differentiated portions of the terrestrial planets - like Earth's continental crust - plays a key role in the presence of accessory minerals like zircon (ZrSiO4) and baddeleyite (ZrO2). In addition to being a cornerstone in the study of geologic time using the Uranium-Lead geochronometer, these accessory minerals are the main carriers of zirconium in the crust and are thus likely to preserve a unique yet unexplored record of the evolution of Zr isotope composition through geologic time. As such, understanding the processes that lead to variability in the isotopic composition of zirconium and how this is recorded in Zr-rich accessory minerals, may provide a window to explore the geochemical evolution of our planet in the deep geologic past, even beyond the oldest preserved rock record currently known in our planet.Shifts in the bonding/coordination environment of tetravalent Zr ions in silicate magmas during zircon and baddeleyite crystallization are expected to result in fractionation (i.e., differential equilibrium incorporation) of its isotopes in precipitated solids and residual melts. This implies that small variations in the abundance of zirconium stable isotopes in terrestrial rocks and minerals have the potential to elucidate how this element behaves and fractionates in high-temperature geological environments. This award will support two early-career investigators to develop techniques to measure zirconium isotopic compositions at high precision and explore, for the first time, the stable zirconium isotopic composition of silicate Earth. The principal goals of this research are threefold: 1) To develop the laboratory materials (e.g., isotopic reference standard and isotopic tracers) necessary for making zirconium isotopic measurements at high-precision. This will be accomplished in collaboration with scientist from the National Institute of Standards and Technology (NIST), who in the future will continue to distribute the standard materials produced during this research; 2) To explore the range of variability in zirconium isotopic abundances of key reservoirs that comprise the solid Earth; 3) Using the newly gained knowledge, explore how variations in the isotopic composition of Zr may be linked to the development, evolution and chemical refinement of the Earth's crust.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

在过去的60年里，锆元素越来越多地被用作破译地球和太阳系中其他‘岩石’行星体的分异历史的工具。尽管在大多数地质环境中是一种“痕量元素”(即浓度相对较低的元素)，但它在类地行星的化学分异部分--如地球的大陆地壳--的优先富集性，在辅助矿物如锆石(ZrSiO4)和斜锆石(ZrO2)的存在中起着关键作用。这些副矿物除了是利用铀-铅地质计时仪研究地质年代的基石外，还是地壳中锆元素的主要载体，因此可能保存着一种独特的、尚未探索的关于锆同位素成分随地质时代演变的记录。因此，了解导致锆同位素组成变化的过程以及这种变化是如何记录在富锆副矿物中的，可能为探索地球深部地质历史的地球化学演化提供一个窗口，甚至超过地球上目前已知的最古老的岩石记录。在锆石和斜晶石结晶过程中，硅酸盐岩浆中四价锆离子的键合/配位环境的变化有望导致其同位素在沉淀固体和残余熔体中的分馏(即微分平衡并入)。这意味着陆地岩石和矿物中的锆稳定同位素丰度的微小变化有可能阐明这种元素在高温地质环境中的行为和分馏。该奖项将支持两名职业生涯早期的研究人员开发高精度测量锆同位素组成的技术，并首次探索硅酸盐地球稳定的锆同位素组成。这项研究的主要目标有三个：1)开发进行高精度的锆同位素测量所需的实验室材料(例如，同位素标准物质和同位素示踪剂)。这将与美国国家标准与技术研究所(NIST)的科学家合作完成，他们将在未来继续分发在这项研究中产生的标准材料；2)探索构成固体地球的关键储集层的锆同位素丰度的可变性范围；3)利用新获得的知识，探索锆同位素组成的变化如何与地球地壳的发展、演化和化学精炼有关。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。