Geochronology using Nucleogenic Neon

该项目将支持开发一种新的方法来确定矿物的形成年龄，特别是那些目前不能用现有技术确定年代的矿物。该方法是基于铀和钍衰变产生的稀有同位素这项技术对赤铁矿和磁铁矿等氧化铁矿物的测年特别有用，并可能适用于了解沉积和热液作用产生的具有重要经济意义的矿床的时间和成因。将对该测年系统的几个重要方面进行研究。首先，将进行一系列实验来确定产生子体同位素的反应18O(&amp；#945；，n)21Ne的核截面。这些实验将包括将已知能量的已知剂量的粒子注入各种目标材料，然后直接测量同位素稀释质谱仪产生的~(21)Ne。更多的实验将表征霓虹在可能被测年的矿物中的扩散系数，这将确定在什么温度条件下可以预期霓虹的保留。这些数据对于准确解释测得的年龄是必要的。最后一组实验将被设计来识别铀和钍的典型水平，以及用于测年的感兴趣矿物中非放射性成因的霓虹灯。这些数据将为哪些类型的矿物是测年方法的有希望的目标提供洞察。

This project will support the development of a new method for determining the formation ages of minerals, especially those that cannot currently be dated with existing techniques. The method is based on the ingrowth of a rare isotope of neon - 21Ne - from the decay of uranium and thorium. This technique should be especially useful for dating of iron oxide minerals such as hematite and magnetite, and will likely be applicable to understanding the timing and origin of economically significant ore deposits produced by both sedimentary and hydrothermal processes.Several important aspects of this dating system will be investigated. First, a set of experiments will be performed to determine the nuclear cross sections for the reaction 18O(α, n) 21Ne, which produces the daughter isotope. These experiments will involve implantation of a known dose of α particles of known energies into various target materials, followed by direct measurement of the 21Ne produced by isotope dilution mass spectrometry. Additional experiments will caharcterize the diffusivity of neon in likely minerals to be dated, which will establish under what temperature conditions neon retention is to be expected. Such data are necessary for accurate interpretation of the measured ages. A final set of experiments will be designed to identify the typical levels of uranium and thorium, as well as non-radiogenic neon, in minerals of interest for dating. These data will provide insight to what types of minerals are promising targets for the dating method.