Discovering Hadean Earth

探索冥古宙地球

• 批准号: 0948724
• 负责人: Timothy Harrison
• 金额: $ 29.9万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-05-15 至 2015-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0948724&HistoricalAwards=false
• 关键词: Discovering; Hadean; Earth

Intellectual merit. The first 500 million years of Earth history - the Hadean Eon - is a period of 'lost' time as there is virtually no rock record preserved from this interval. However, the PI and colleagues have samples of detrital and xenocrystic zircons from western Australia (Jack Hills) with ages between 4.0 and 4.4 Ga. A massive analysis campaign has identified many thousands of these ancient zircons, and investigations of these grains have been interpreted to suggest the presence of liquid water at the Earth's surface, significant growth of continental crust, a mature sediment recycling system, and perhaps operation of plate boundary-type processes during the Hadean. Such evidence suggests the possibility that the very early planet was much more similar to the present day Earth than previously thought and this stimulates and justifies new measurements. Analytical developments, analysis programs, and experiments are proposed to address the following questions: 1) Could Hadean Jack Hills zircons have been formed by impacts? 2) Do Hadean zircons record the terrestrial counterpart to the ~3.9 Ga lunar cataclysm? 3) What happened to the highly enriched (low Lu/Hf) reservoir seen in 3.9- 4.3 Ga zircons? 4) Do mineral inclusions in 4 Ga zircons retain a pristine Hadean record? 5) Are available barometers applicable to inclusions in Hadean zircons? 6) Do Pu-U variations in Hadean zircons reflect water-mediated fractionation? and 7) Are the collective isotopic, mineralogical, and thermometry data evidence of Hadean continental recycling and plate boundary interactions? Proposed investigations include: 1) Laser ablation ICPMS measurement of initial 176Hf/177Hf in 3.9-3.6 Ga zircons, 2) U-Th-Pb ion microprobe depth profiling of 4 Ga zircons, and 3) characterization of zircons formed in terrestrial impact melts, 4) Hadean Pu-U geochemistry from fission Xe isotopes, 5) Nd isotopic systematics of Jack Hills zircon, 6) NanoSIMS analysis of Si/Al in micron-sized muscovite, 7) K-Ca dating of Hadean muscovite inclusions, and 8) calibration of the Si-in-muscovite barometer forperaluminous granitoids.Broader Impacts. This research will directly benefit the UCLA graduate students supported by this project. Once trained on the ion microprobe, these students in turn provide support to visitors (including numerous graduate students) to the NSF-supported Keck Center for Isotope Geochemistry (see below). Several small projects have been identified that will be used to engender undergraduate research opportunities.Research outcomes are of international interest and could be akin to the results of a planetary exploration mission if the Hadean paradigm is overturned. This project showcases scientific and technical leadership in a field of global interest, aids in capturing the imagination of young people considering a career in science and technology, and provides training opportunities for young scientists. Research results will be communicated to the scientific community via high citation impact scientific journals and to the public through sustained outreach activities (see http://sims.ess.ucla.edu/outreach/outreach.php).

智力优点。地球历史的前5亿年 - 哈迪斯·埃恩（Hadean Eon）是“丢失”时间的时期，因为此间隔几乎没有岩石记录。 However, the PI and colleagues have samples of detrital and xenocrystic zircons from western Australia (Jack Hills) with ages between 4.0 and 4.4 Ga. A massive analysis campaign has identified many thousands of these ancient zircons, and investigations of these grains have been interpreted to suggest the presence of liquid water at the Earth's surface, significant growth of continental crust, a mature sediment recycling system, and perhaps operation of plate boundary-type Hadean期间的过程。这些证据表明，早期的星球与当今地球的可能性比以前的想法更相似，这刺激并证明了新的测量值。提出了分析开发，分析计划和实验来解决以下问题：1）Hadean Jack Hills锆石是否会因影响形成吗？ 2）Hadean锆石记录到〜3.9 GA月球灾难的地面对应物？ 3）在3.9- 4.3 Ga锆石中看到的高度丰富（低LU/HF）水库发生了什么？ 4）4 GA锆石中的矿物包含保留原始的Hadean记录？ 5）可用于适用于Hadean锆石的夹杂物的气压计吗？ 6）Hadean锆石的PU-U是否反映了水介导的分馏？ 7）集体的同位素，矿物学和温度计数据证据是否具有Hadean大陆回收和板边界相互作用？拟议的研究包括：1）激光消融ICPMS在3.9-3.6 Ga锆石中对初始176hf/177hf的测量，2）u-th-pB离子微探针深度分析4 Ga锆石，以及3）在陆地上造影融合中形成的锆石的表征，4）hisean pu-usions for-i is pu-u-u is forotition fropient fortient fortient fortient frotient fortient frotient frotient frotient frotient frotient frotient frotient forotation frotient frotient frotot frotient frotient frotity frotot xee，杰克山锆石，6）在微米大小的白云母中对Si/al的纳米sims分析，7）hadean麝香木夹杂物的k-ca定期，以及8）校准Siin-in-in-in-in-in-in-in-in-in-in-muscovite型凸仪型孔：Broader的效果。这项研究将直接受益于该项目支持的UCLA研究生。一旦接受了离子微探针的培训，这些学生又向访客（包括众多研究生）提供了支持NSF支持的同位素地球化学中心（见下文）。已经确定了几个小型项目，这些项目将用于引发本科研究机会。研究结果具有国际兴趣，如果颠覆了Hadean范式，则可能类似于行星勘探任务的结果。该项目在全球兴趣领域展示了科学和技术领导力，有助于捕捉考虑科学和技术职业的年轻人的想象，并为年轻科学家提供培训机会。研究结果将通过高引文来传达科学界的科学期刊，并通过持续的外展活动与公众传达（请参阅http://sims.ess.ucla.edu/outreach/outreach/outreach.php）。