Global Change: Geologic Records Inferred from Cosmic Ray Produced Neon at the Surface of the Earth

全球变化：从地球表面产生的宇宙射线推断的地质记录

• 批准号: 9220048
• 负责人: Kurt Marti
• 金额: $ 6.36万
• 依托单位: University of California-San Diego
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1993
• 资助国家: 美国
• 起止时间: 1993-01-15 至 1993-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9220048&HistoricalAwards=false
• 关键词: Global; Change; Geologic; Records; Inferred

In the last few years, several cosmic-ray-produced radionuclides (10Be, 14C, 26Al, 36Cl), as well as stable 3He, 21Ne and 22Ne have been discovered in terrestrial surface materials. Some of these nuclides are already employed as tracers in studies of geophysical and geological phenomena and open up a new field of study and are expected to provide essential data on rates of change in global change research. Such studies require an accurate knowledge of of the production rates, present and past, which are not currently available. We are using a direct method for the determination of some of present production rates, by exposing relevant targets at mountain altitudes. Production rates averaged over the last solar cycles can be obtained by comparing production rates with neutron monitor data. We are currently evaluating the relevant production ratio P21/P26 of the cosmic-ray-produced nuclides 21Ne and 26Al by isotopic measurements of Ne in quartz samples. Our preliminary experimental data do not agree well with theoretical predictions. Average production rates over 104-105years can be obtained from measurements of samples of known age. Measurements of the 3He/21Ne ratio show that 3He is often incompletely retained in quartzites. Therefore, 21Ne production rates and 21Ne/10Be and 21Ne/26Al ratios provide essential information, which is required to evaluate erosion rates and to define geological processes (uplift, variations in ice cover etc).

在过去几年中，在地球表面材料中发现了几种宇宙射线产生的放射性核素（10Be、14C、26Al、36Cl）以及稳定的 3He、21Ne 和 22Ne。 其中一些核素已被用作地球物理和地质现象研究的示踪剂，开辟了一个新的研究领域，并有望为全球变化研究提供有关变化率的重要数据。 此类研究需要准确了解当前和过去的生产率，但目前尚无法获得。 我们正在使用直接方法，通过在山区海拔处暴露相关目标来确定一些当前的生产率。 通过将生产率与中子监测数据进行比较，可以获得最后一个太阳周期的平均生产率。 我们目前正在通过石英样品中氖的同位素测量来评估宇宙射线产生的核素 21Ne 和 26Al 的相关生产比 P21/P26。 我们的初步实验数据与理论预测不太吻合。 104-105 年的平均生产率可以通过测量已知年龄的样本来获得。 3He/21Ne 比值的测量表明，3He 通常不完全保留在石英岩中。 因此，21Ne 生产率以及 21Ne/10Be 和 21Ne/26Al 比率提供了评估侵蚀速率和定义地质过程（隆起、冰盖变化等）所需的重要信息。