Partitioning of Noble Gases Between Crustal Minerals: Implications for Geochronology

基于惰性气体的热年代计（特别是40 Ar/39 Ar和U-Th/He）代表了地质过程中限制速率和时间的重要方法-特别是关于地壳和地球表面的热演化和构造演化。 定量模型最近已经开发出来，可以预测和量化“过剩Ar”-一个常见的，但在标准热年代学知之甚少的问题。 为了在自然系统中充分实施和测试模型，需要地壳阶段之间的Ar（和He）分区数据。 虽然矿物/流体分配存在广泛的限制，但同样重要的矿物/矿物分配数据很少和/或有争议。 拟议的研究旨在：1）测量Ar（和其他稀有气体，He和Ne）在常见的地壳矿物之间的相对分配，并在这样做的过程中，2）测试假设，某些矿物，如石英，可能作为重要的汇Ar在地壳内，从而发挥关键作用，限制过剩的Ar在其他周围的矿物。将进行活塞缸实验，以测量常见的地壳相，包括石英，云母，和长石之间的平衡分配的Ar。 实验将使用反应堆产生的37 Ar来监测惰性气体在矿物之间的分配。 将使用紫外激光和/或卢瑟福背散射对平衡矿物表面进行分析。 预计未来的实地应用这项研究。 拟议活动的更广泛的影响包括研究生的教育和培训，以及涉及伦斯勒理工学院和英国开放大学同事的PI合作研究计划的发展。

Noble gas based thermochronometers (notably 40Ar/39Ar and U-Th/He) represent an important method of constraining rate and time in geologic processes - particularly regarding the thermal and tectonic evolution of the crust and surface of the Earth. Quantitative models have recently been developed which can predict and quantify "excess Ar" - a common yet poorly understood problem in standard thermochronology. In order for the models to be fully implemented and tested in natural systems, Ar (and He) partitioning data among crustal phases is needed. While broad constraints exist for mineral/fluid partitioning, equally important mineral/mineral partitioning data is scant and/or controversial. The proposed research is designed to: 1) Measure the relative partitioning of Ar (and other noble gases, He and Ne) between common crustal minerals, and in so doing, 2) test the hypothesis that certain minerals, such as quartz, may act as important sinks for Ar within the crust, thus playing a key role in limiting excess Ar in other surrounding minerals. Piston-cylinder experiments will be conducted to measure the equilibrium partitioning of Ar between common crustal phases including quartz, micas, and feldspars. The experiments will employ reactor-produced 37Ar to monitor noble gas partitioning among minerals. Analysis of equilibrated mineral surfaces will be performed using UV-laser and/or Rutherford Backscattering. Future field-based applications of this research are anticipated. The broader impacts of the proposed activities include the education and training of a graduate student as well as the development of the PI's collaborative research program involving colleagues at Rensselaer Polytechnic Institute and at the Open University, England.