Cosmogenic Isotopes Produced In Situ in Terrestrial Rocks: Quantifying the Effect of Elevation on the Production Rates

陆地岩石中原位产生的宇宙成因同位素：量化海拔对生产率的影响

• 批准号: 0001191
• 负责人: Marek Zreda
• 金额: $ 8.82万
• 依托单位: University of Arizona
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-07-01 至 2002-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0001191&HistoricalAwards=false
• 关键词: Cosmogenic; Isotopes; Produced; Situ; Terrestrial

EAR-0001191ZredaThe goal of this proposal is to determine how production rates of in-situ cosmogenic isotopes change with elevation. This goal will be achieved by measuring cosmogenic 36Cl and/or 3He in samples from lava flows that extend over long distances in the vertical. Hawaii is the ideal location for this project because: (1) many very long lava flows have been mapped (some extend over 2 km in the vertical); (2) the stratigraphy of lava flows is well established; (3) individual flows can be traced in the field, thus making it possible to ensure that samples are collected from the same lava flow; and (4) many flows are well dated, thus making it possible to combine attenuation lengths from two or more lava flows into a composite record. At least ten samples from different elevations will be measured in each lava flow, and the concentration of accumulated cosmogenic isotopes will be expressed as a func-tion of elevation. Data from individual lava flows will then be combined and a composite function describing the dependence of production rates on elevation will be developed. This function will be compared with the measured neutron intensity, and the applicability of the measured neutron atten-uation length over geological time scales will be assessed. Finally, improved altitudinal scaling for-mulation for cosmogenic production rates will be constructed, which should be an important contribution to the improvement of all cosmogenic dating methods.

EAR-0001191Zreda 该提案的目标是确定原位宇宙成因同位素的生产率如何随海拔变化。这一目标将通过测量垂直延伸很长距离的熔岩流样本中的宇宙成因 36Cl 和/或 3He 来实现。夏威夷是该项目的理想地点，因为：（1）已经绘制了许多非常长的熔岩流（有些垂直延伸超过 2 公里）； (2) 熔岩流的地层学已十分确定； （3）可以在现场追踪各个熔岩流，从而可以确保样品是从同一熔岩流中采集的； (4)许多熔岩流都有很好的年代记录，因此可以将两个或多个熔岩流的衰减长度组合成一个复合记录。每个熔岩流中将测量至少十个来自不同海拔的样本，并且累积的宇宙同位素的浓度将表示为海拔的函数。然后将合并来自各个熔岩流的数据，并开发描述生产率对海拔的依赖性的复合函数。该函数将与测量的中子强度进行比较，并评估测量的中子衰减长度在地质时间尺度上的适用性。最后，将构建改进的宇宙成因生产率的海拔尺度公式，这应该对所有宇宙成因测年方法的改进做出重要贡献。