Partitioning of Noble Gases Between Crustal Minerals: Implications for Geochronology

稀有气体热时计（特别是40Ar/39Ar和U-Th/He）是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和构造演化。最近开发了定量模型，可以预测和量化“过量氩”-这是标准热年代学中一个常见但知之甚少的问题。为了使模型在自然系统中充分实现和测试，需要在地壳相之间进行Ar（和He）划分数据。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。提出的研究旨在：1)测量氩（以及其他稀有气体，He和Ne）在普通地壳矿物之间的相对分配，并在此过程中，2)验证某些矿物，如石英，可能是地壳中氩的重要汇，从而在限制其他周围矿物中过量的氩方面发挥关键作用的假设。将进行活塞-圆筒实验，测量石英、云母和长石等常见地壳相之间Ar的平衡分配。实验将使用反应堆产生的37Ar来监测稀有气体在矿物之间的分配。平衡矿物表面的分析将使用紫外激光和/或卢瑟福后向散射进行。展望了该研究未来的实地应用。拟议活动的更广泛影响包括研究生的教育和培训，以及PI的合作研究计划的发展，该计划涉及伦斯勒理工学院和英国开放大学的同事。

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.