Geologic Records Inferred Form Cosmic Ray Produced Neon at the Surface of the Earth

地质记录推断地球表面宇宙射线产生的氖气

• 批准号: 9119163
• 负责人: Kurt Marti
• 金额: $ 5.96万
• 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: 1992
• 资助国家: 美国
• 起止时间: 1992-01-15 至 1993-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9119163&HistoricalAwards=false
• 关键词: Geologic; Records; Inferred; Form; Cosmic

In the last few years, several cosmic-ray-produced radionuclides (10Be, 14C, 26Al, 36Cl), as well as stable, 3He, Ne 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 the production rates, present and past, which are not currently available. The relevant excitation functions for different nuclides are not known. A simulation of the cosmic ray flux is a rather complex endeavor. We propose 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 propose to determine the relevant production ratio P21/P26 of the cosmic-ray- produced nuclides 21Ne and 26Al by isotopic measurements of Ne in quartz samples. Average production rates over 104-105 years can be obtained from measurements of samples of known age. Measurements of the 3He/21Ne ratio show and that 3He is often incompletely retained in quartzites. Therefore, 21Ne production rates and 21Ne/10Be and 21Ne/Al ratios provide essential information, which is required to evaluate erosion rates and to define geological processes (uplift, variations in ice cover etc).

最近几年，在地球表面物质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、Ne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，可望提供有关全球变化研究变化率的基本数据。这样的研究需要对现在和过去的生产率有准确的了解，而这是目前无法获得的。不同核素的相关激发函数尚不清楚。宇宙射线通量的模拟是一项相当复杂的工作。我们提出了一种直接确定目前某些生产率的方法，即在山区暴露相关目标。上一个太阳周期的平均生产率可以通过将生产率与中子监测数据进行比较来获得。我们建议通过对石英样品中Ne的同位素测量来确定宇宙线产生的核素21Ne和26Al的相应产额比P21/P26。104-105年的平均生产率可以通过测量已知年龄的样品来获得。~(31)He/~(21)Ne比值测量表明，~(3)He常不完全保留在石英岩中。因此，21Ne产出率和21Ne/10Be和21Ne/Al比值提供了必要的信息，这是评估侵蚀速率和确定地质过程(抬升、冰盖变化等)所必需的。