Xenon Isotopes in Mid Ocean Ridge and Ocean Island Basalts: Implications for the Volatile Evolution of the Earth

大洋中脊和洋岛玄武岩中的氙同位素：对地球波动演化的影响

• 批准号: 0911363
• 负责人: Sujoy Mukhopadhyay
• 金额: $ 19.44万
• 依托单位: Harvard University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-07-01 至 2012-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0911363&HistoricalAwards=false
• 关键词: Xenon; Isotopes; Mid; Ocean; Ridge

"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)."The Iodine-Xenon and Plutonium-Uranium-Xenon radioactive decay systems are the only ones that can provide constraints on the timing and rates of degassing from the Earth's mantle during the first couple hundred million years of the Earth's history. Dissecting the timescale of mantle degassing is important for understanding the compositions of the major gases that were present in the Earth's early atmosphere. For example, if most of the degassing of the Earth's mantle is accomplished before the mantle gets oxidized, particularly prior to the formation of the Earth's core, the early atmosphere would have a reducing composition (Hydrogen, Carbon Monoxide, Methane). On the other hand, a more delayed degassing would have led to a neutral or slightly oxidizing atmosphere (Carbon Dioxide, Water, Nitrogen). Understanding which of these two scenarios is most probable would have great implications for the state of the pre-biotic chemistry on the Earth's surface.Recent technical advances in the Noble Gas Laboratory at Harvard now make it possible to detect small isotopic anomalies in Xenon in mantle derived basalts. Therefore, a suite of heavy noble gas measurements (Neon, Argon, Krypton, Xenon) in basalts from mid-ocean ridges in the Atlantic, Pacific, and Indian Ocean, along with basalt samples from hotspots such as Hawaii and Iceland is proposed. In particular, the research will address whether there are variations in Plutonium/Iodine ratios within the mantle and whether the Xenon and Argon compositions of the upper mantle resembles the Sun, chondritic meteorites, or air. The results obtained from the proposed research would provide new information on sources of volatiles to planet Earth, the timing of degassing of the Earth's mantle, and the volatile evolution of planet Earth.

“该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。“碘-氙和钚-铀-氙放射性衰变系统是唯一能够在地球历史的头几亿年中限制地幔脱气的时间和速率的系统。剖析地幔脱气的时间尺度对于理解地球早期大气中主要气体的组成是很重要的。例如，如果地球地幔的大部分脱气是在地幔被氧化之前完成的，特别是在地核形成之前，早期的大气层将具有还原性成分（氢，一氧化碳，甲烷）。另一方面，更延迟的脱气将导致中性或轻微氧化性气氛（二氧化碳、水、氮气）。了解这两种情况中的哪一种最有可能对地球表面的前生物化学状态有很大的影响。哈佛大学惰性气体实验室最近的技术进步使探测地幔玄武岩中氙的同位素异常成为可能。因此，一套重惰性气体测量（氖，氩，氪，氙）的玄武岩中的大洋中脊在大西洋，太平洋和印度洋，沿着与玄武岩样品的热点，如夏威夷和冰岛的建议。特别是，研究将解决地幔内钚/碘比率是否存在变化，以及上地幔的氙和氩成分是否类似于太阳，南极陨石或空气。从拟议的研究中获得的结果将提供有关地球挥发物来源、地球地幔脱气时间以及地球挥发性演化的新信息。