Ar Dating of Near-Surface Faulting

对韧性剪切带进行放射性定年已经彻底改变了人们对断层演化和地壳深部过程的认识，然而，由于一些因素使得对数据的解释更加困难，使用放射性方法对脆性近地表断层进行定年还没有得到普遍应用。近地表条件下的主要问题之一是存在既属于碎屑（原生）又属于自生（次生）的矿物相。因此，对这类岩石的放射性测年通常得出的“年龄”反映了初级和次级粘土形成事件的混合。该项目将使用这种混合源年龄谱和方法来确定碎屑与自生阶段的百分比，以计算自生末端成员的年龄。研究结果将进一步完善这一方法，并为几个重要的浅层断层提供初步的现场应用。

9980459HallRadiometric dating of ductile shear zones has revolutionized understanding of fault evolution and deep-crustal processes, however use of radiometric methods to date brittle, near surface faulting has not been generally utilized, as several factors make the interpretation of the data much more problematic. One of the major problems at near-surface conditions is the presence of mineral phases that are both detrital (primary) and authigenic (secondary) in origin. Therefore, radiometric dating of such rocks typically results in an "age" that reflects a mixture of primary and secondary clay forming events. This project will use such mixed-source age spectra along with methodology to determine the percentages of detrital vs. authigenic phases to calculate the authigenic end member age. Results should refine this approach and provide preliminary field applications to several important shallow-level faults.