New advances in Ar-Ar geochronology and applications to geoscience

Ar-Ar地质年代学新进展及其在地球科学中的应用

• 批准号: 184211-2006
• 负责人: Lee, James
• 金额: $ 2.17万
• 依托单位: Queen's University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2007
• 资助国家: 加拿大
• 起止时间: 2007-01-01 至 2008-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=363690
• 关键词: New; advances; Ar; geochronology; applications

One of the most useful methods of dating rocks ("geochronology") is based on the radioactive decay of potassium (40K) to argon (40Ar), which serves as a long-lived clock over the vast span of geologic and astronomic time. The 40Ar/39Ar dating technique - a variant of the K-Ar dating method - is considered to be one of the most powerful tools currently used in research laboratories worldwide. Understanding the significance of the ages we obtain from such clocks requires a detailed understanding of how the elemental atoms and ions can move through the rocks and crystals in which they accumulate, in a fundamental process known as diffusion. Many factors such as crystal structure, mineral chemistry, Ar solubility, and the presence of defects or flaws in the crystal structure control diffusional behaviour and the effect of these factors will be studied in laboratory experiments and through numerical modelling in two of the most common rock-forming and commonly dated minerals - mica and feldspar. Improved knowledge of these effects may explain enigmatic age discrepancies between different minerals using different geochronological clocks, where rocks in southeastern BC will serve as an ideal field experiment.  Knowledge of all of these fundamental controls will be applied to significant geological problems in Latin and South America, in order to determine the timing of the motions of lithospheric plates around Mexico around 450 million years ago, test models for the formation of large gold deposits in the central Andes, and improve exploration strategies for these deposits in the region, which is a major area of investment for the Canadian mining industry. Thus, the proposed research addresses several fundamental but related questions in geochronology, ore-deposit formation, and plate tectonics.

测定岩石年代最有用的方法之一（“地质年代学”）是基于钾（40K）到氩（40Ar）的放射性衰变，它在巨大的地质和天文时间跨度中充当了一个长寿的时钟。40Ar/39Ar测年技术是K-Ar测年法的一种变体，被认为是目前世界各地研究实验室使用的最强大的工具之一。要理解我们从这种时钟中获得的年龄的意义，就需要详细了解元素原子和离子是如何在它们聚集的岩石和晶体中移动的，这是一个被称为扩散的基本过程。许多因素，如晶体结构，矿物化学，Ar溶解度，以及晶体结构中存在的缺陷或缺陷控制扩散行为，这些因素的影响将在实验室实验中进行研究，并通过两种最常见的岩石形成和常用的矿物-云母和长石的数值模拟。对这些影响的进一步了解可以解释不同矿物之间神秘的年龄差异，使用不同的地质年代时钟，不列颠哥伦比亚省东南部的岩石将作为一个理想的实地实验。所有这些基本控制的知识将应用于拉丁美洲和南美洲的重大地质问题，以确定大约4.5亿年前墨西哥周围岩石圈板块运动的时间，测试安第斯山脉中部大型金矿形成的模型，并改进该地区这些矿床的勘探策略，这是加拿大采矿业投资的主要领域。因此，提出的研究解决了地质年代学、矿床形成和板块构造学中几个基本但相关的问题。