Geochronology using Nucleogenic Neon

该项目将支持开发一种新方法，用于确定矿物的形成年龄，特别是那些目前无法用现有技术确定年代的矿物。该方法是基于一种稀有的氖同位素-21 Ne-从铀和钍的衰变中向内生长。这一技术对氧化铁矿物如赤铁矿和磁铁矿的定年特别有用，并可能适用于了解沉积和热液过程产生的具有经济意义的矿床的时间和起源。首先，将进行一组实验以确定产生子体同位素的反应18 O（#945;，n）21 Ne的核截面。这些实验将涉及植入已知剂量的α将已知能量的粒子注入各种靶材料中，然后直接测量同位素稀释质谱法产生的21 Ne。更多的实验将测定氖在可能要测年的矿物中的扩散率，这将确定在什么温度条件下氖会被保留。这些数据对于准确解释测得的年龄是必要的。将设计最后一组实验，以确定铀和钍的典型水平，以及非放射性氖，在感兴趣的矿物测年。这些数据将提供洞察什么类型的矿物是有希望的目标的定年方法。

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.