Zircons Are Forever

锆石永恒

• 批准号: 0207340
• 负责人: John Valley
• 金额: $ 39.32万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-07-01 至 2006-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0207340&HistoricalAwards=false
• 关键词: Zircons; Forever; Zircons; Forever

EAR-0207340ValleyThis project will investigate the magmatic history of the Earth's crust over the past 4.4 billion years. The mineral zircon will be analyzed for oxygen isotope ratio, U-Pb age, and rare earth element concentration. The high melting temperature, chemical inertness, and hardness of zircon creates a time capsule of geochemical information that lasts virtually forever in samples with low amounts of radiation damage. New ion microprobe and laser techniques for high precision and accuracy, and/or high spatial resolution will be employed. Single domains within zoned zircons will be analyzed. Igneous minerals will be studied from selected terranes of early Archean, Proterozoic and Mesozoic through Cenozoic age. Archean samples will include detrital zircons from the Jack Hills, Western Australia, where we discovered the oldest known sample of the Earth in the past grant period. The younger samples will document processes of crustal reworking in the Idaho and Sierra Nevada batholiths of the western U.S. Analyses of zircon will be compared to new data for magmatic garnet, baddeleyite, titanite, epidote, rutile and quartz. In combination, these results will provide a record of evolving compositions including pre-magmatic xenocrysts, magmatic phenocrysts and a range of post magmatic alteration minerals. These studies of zircons and associated igneous minerals will have broad significance for understanding the origin and evolution of the Earth's crust. Studies of the Archean (4.0 to 4.4 Ga) zircons provide the only evidence of the earliest conditions on Earth. The recent hypothesis of a "Cool early Earth" will be tested, which has implications for the timing of the first oceans and the origin of life.

EAR-0207340VALLEYTHIS项目将在过去44亿年内调查地壳的岩浆历史。将分析矿物锆石的氧同位素比，U-PB年龄和稀土元素浓度。锆石的高熔化温度，化学惰性和硬度会产生一个地球化学信息的时间胶囊，几乎可以永远持续到辐射损害量较低的样品中。新的离子微探针和激光技术将采用高精度和准确性和/或高空间分辨率。将分析锆石中的单个域。将从早期的大将，原始生代和中生代到新生代时代的成熟地面研究火成岩的矿物质。大将样本将包括来自西澳大利亚州杰克山的碎屑锆石，在那里我们发现了过去的赠款时期最古老的地球样本。年轻的样本将记录在美国西部的爱达荷州和内华达州内华达山脉中的地壳重制的过程，将锆石分析的分析与岩浆，Baddeleyite，titanite，Epidote，pidote，lutile，lutile和Quartz的新数据进行比较。结合起来，这些结果将提供不断发展的组合物的记录，包括前Xenocrysts，Magmatic Shocrysts和一系列岩浆后改变矿物质。这些对锆石和相关的火成岩矿物的研究将在理解地壳的起源和演变方面具有广泛的意义。对大帝（4.0至4.4 GA）锆石的研究提供了地球上最早条件的唯一证据。将测试“凉爽早期地球”的最近假设，这对第一海的时机和生命的起源具有影响。