40Ar/39Ar Dating of Feldspars from the KTB Deep Drill Hole: Insight into Post-Orogenic Thermal Relaxation and AR Diffusion Systematics During Closure

KTB 深钻孔长石的 40Ar/39Ar 测年：洞察闭合过程中造山后热弛豫和 AR 扩散系统学

• 批准号: 9219595
• 负责人: Peter Zeitler
• 金额: $ 10.32万
• 依托单位: Lehigh University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1993
• 资助国家: 美国
• 起止时间: 1993-09-01 至 1996-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9219595&HistoricalAwards=false
• 关键词: 40Ar; 39Ar; Dating; Feldspars; KTB

9219595 Zeitler The 40Ar/39Ar dating of feldspar has enormous potential for helping geologists determine quantitative temperature-time paths over the range of 150oC to 350oC. Such time-temperature information over such a range of low temperatures is of great importance to scientists evaluating such issues as the architecture and evolution of the crust or the origin and evolution of sedimentary basins and their attendant water and hydrocarbon resources. However, to this point the technique has only been tested in short-term laboratory heating experiments and in presumably well-characterized geological contexts. Now that sophisticated interpretative models have been developed for use in quantitative thermochronometry, it is important that the 40Ar/39Ar dating of feldspar be evaluated in a slow-cooling geological environment. The KTB deep drill hole in Germany offers an ideal natural laboratory with which to examine the closure of feldspar to diffusive Ar loss during slow cooling, as this hole already has reached temperatures which overlap the closure interval for feldspars and is projected to reach ~300oC. In this project, a suite of samples from deep in the KTB hole will be examined which will permit the principal investigator to view the process of Ar closure as it is happening, and would be an invaluable benchmark for virtually all applied studies which use feldspar thermochronometry. At the same time, the understanding of 40Ar/39Ar systematics in feldspar is sufficiently good that study of shallow samples from the KTB hole will permit the principal investigator to monitor in detail the post-orogenic cooling of the local crust; he will assess the relative roles that thermal relaxation and denudation have played, and will look for evidence of even a very mild Tertiary thermal event that might be responsible for the high gradients seen in the KTB hole. Such information will be highly useful for models of thermal evolution of the lithosphere du ring and after mountain building. ***

小行星9219595 长石的40 Ar/39 Ar定年具有巨大的潜力，可以帮助地质学家确定150 oC至350 oC范围内的定量温度-时间路径。 这种低温范围内的时间-温度信息对于科学家评估地壳的结构和演变或沉积盆地的起源和演变及其伴随的水和碳氢化合物资源等问题具有重要意义。 然而，到目前为止，这项技术只在短期的实验室加热实验中进行了测试，并在可能具有良好特征的地质环境中进行了测试。 现在，复杂的解释模型已被开发用于定量热年代学，重要的是，长石的40 Ar/39 Ar定年在缓慢冷却的地质环境中进行评估。 德国的KTB深钻孔提供了一个理想的天然实验室，用于检查长石在缓慢冷却过程中对扩散性Ar损失的闭合，因为该钻孔已经达到了与长石闭合区间重叠的温度，预计将达到~ 300 oC。 在这个项目中，将检查一套来自KTB孔深处的样品，这将允许主要研究人员查看Ar闭合过程，因为它正在发生，并且将成为几乎所有使用长石热计时法的应用研究的宝贵基准。 与此同时，对长石中40 Ar/39 Ar系统学的了解已经足够好，对KTB孔浅层样品的研究将使首席研究员能够详细监测当地地壳的造山后冷却;他将评估热松弛和剥蚀所起的相对作用，并将寻找证据，即使是一个非常温和的第三纪热事件，可能是负责在KTB孔看到的高梯度。 这些信息将是非常有用的岩石圈的热演化模型期间和造山后。 ***