SGER: Cosmogenic Dating of the Hilo Core, Hawaii

9526126基性熔岩的Zreda序列包含地球上宇宙射线强度的记录。 然而，这种熔岩很难准确地确定年代，特别是在14 C范围之外，因为它们的晶体结构很细，钾含量很低。 宇宙成因核素的原位积累可以潜在地用于解决这个问题。 我建议测试一种新的宇宙成因的方法，以确定现在埋藏的镁铁质熔岩流的年龄和/或宇宙射线强度在过去。 它使用两种半衰期不同的宇宙成因核素。 一种寿命较长或稳定的核素的积累被用来确定熔岩在地表暴露了多久。 寿命较短的核素的衰变给出了埋藏时间。 将使用从夏威夷希洛1056米岩芯中选取的样品对这种新方法的可行性进行测试。 这项初步研究有三个目标：（1）评价宇宙成因惰性气体的保留情况;（2）评价长寿命宇宙成因放射性核素作为照射时间尺度的效用;（3）评估短寿命宇宙成因核素作为埋藏时间尺度的效用。 如果这种方法成功，它将使我们能够同时确定熔岩流的宇宙成因年龄和暴露于大气层期间的宇宙射线强度。 该项目的初步结果将用于今后的建议，以便对该火山序列和其他火山序列进行全面的宇宙成因研究。

9526126 Zreda Sequences of mafic lavas contain records of the cosmic ray intensity on earth. Such lavas, however, are difficult to accurately date, especially beyond the 14C range, because of their fine-crystalline texture an low potassium content. The in situ accumulation of cosmogenic nuclides can be potentially used to approach this problem. I propose to test a new cosmogenic approach to determine the age of now-buried mafic lava flows and/or the cosmic-ray intensity in the past. It uses two cosmogenic nuclides with different half-lives. The accumulation up of a longer-lived or stable nuclide is used to determine how long the lava had been exposed at the surface. the decay of a shorter-lived nuclide gives the burial duration. The feasibility of this novel approach will be tested using selected samples from the 1056-m core at Hilo, Hawaii. This preliminary study has three objectives: (1) to evaluate the retention of cosmogenic noble gases; (2) to evaluate the utility of long-lived cosmogenic radionuclides as a measure of the exposure duration; and (3) to assess the utility of shorter-lived cosmogenic nuclides as a measure of the burial duration. If the approach is successful, it will enable us to simultaneously determine cosmogenic ages of lava flows and the cosmic ray intensity during their exposure to the atmosphere. Preliminary results in this project will be used in future proposals to perform a comprehensive cosmogenic study on this and other volcanic sequences.