(U-Th)/He Geochronometry and Thermochronometry

Farleyweek-0105981（U-Th）/He测年的技术和应用在过去几年中迅速发展，这是由于这款新恢复的计时器具有较低的封闭温度和相对较高的分析精度。该提案寻求资金，以继续在加州理工学院进行广泛的努力，以改善和扩大（U-Th）/He测年方法。在磷灰石热计时法的情况下，几个重要的问题仍然需要研究，以确保该方法的置信度和可靠性。此外，初步工作表明，其他矿物也可能用于（U-Th）/He定年，并可能提供新的方法来解决重要的地质问题。这些都是拟议工作要探讨的主要问题。更具体地说，该提案的目标是：1）开发和实施新的实验技术，用于评估He扩散系数，目的是建立一个强大的理解是什么因素最终控制He扩散; 2）开发的理解，为什么偶尔磷灰石样品产生不稳定的He年龄，并测试新的分析方法，通过它来规避这些问题;（3）利用新发展的激光加热技术探讨磷灰石颗粒间年龄不均匀性的成因和意义;（4）极年轻火山岩样品测年方法的发展和初步应用（100万年到几百万年），特别是对U系列不平衡后果的评估，（5）探索（U-Th）/He技术用于风化层中Fe、Mn氧化物的定年。

FarleyEAR-0105981Techniques and applications of (U-Th)/He dating have grown rapidly in the last several years due to the low closure temperature and relatively high analytical precision of this newly revitalized chronometer. This proposal seeks funds to continue ongoing, broad efforts at Caltech to improve and expand methods of (U-Th)/He dating. In the case of apatite thermochronometry, several important questions remain to be investigated to assure confidence and reliability of the method. In addition, preliminary work indicates that other minerals may also be of use for (U-Th)/He dating and may provide new ways to address important geologic problems. These are the major issues to be explored by the proposed work. More specifically, the proposal objectives are 1) development and implementation of new experimental techniques for assessing He diffusion coefficients with the goal of establishing a robust understanding of what factors ultimately control He diffusion; 2) development of an understanding of why occasional apatite samples yield erratic He ages, and testing of new analytical methods by which to circumvent these problems; 3) exploration of the origin and significance of apatite grain-to-grain age heterogeneity using the newly developed laser heating technique; 4) development and initial application of methods for dating of extremely young volcanic samples (10's of kyr to few Myr), and in particular assessment of the consequences of U-series disequilibrium, and 5) exploration of the use of (U-Th)/He techniques for dating of Fe and Mn oxides produced in weathering horizons.