CAREER: Refining zircon (U-Th)/He deep-time thermochronology for constraining Neoproterozoic thermal histories

低温热年代学的重点是了解地壳上10公里岩石的热历史。这套热年代学技术已成为了解活动或地质年轻的造山带中岩石抬升和侵蚀的时间和速率的关键。该项目重点关注深时（即前寒武纪）热历史中一个特别有前途和新兴的研究领域。深时热年代学可以用来限制在100-1000万年的时间跨度内发生的加热和冷却的多个阶段。该项目将研究侵蚀的时间和规模，创造了新元古代-寒武纪大不整合在美国大陆中部的锆石（铀钍）/氦热年代学。作为该项目的一部分，获得的侵蚀限制将作为大气-生物圈-岩石圈反馈调查的关键输入，这些反馈将侵蚀估计与1）Rodinia超大陆的解体，2）雪球地球冰川的潜在触发因素，以及3）寒武纪生物多样性爆发。该项目还将寻求进一步改进锆石（铀-钍）/氦热时计的温度灵敏度。该项目包括一个推广和教育计划，旨在通过使用伊利诺伊大学提供的世界级资源：珍本书和曼尼托图书馆，向本科生和公众灌输对深时间概念的理解。该图书馆收藏了大量可追溯到启蒙运动时期的稀有地质书籍和手稿，这些书籍和手稿将用于展览并纳入地质学课程。这些活动将传授地质年代概念的文化知识，培养对地球科学家如何思考的更深层次的理解，并允许本科生参与前现代的主要文献，以提供历史背景和他们的科学目标的基本问题。这个项目的重点是推进深时锆石（U-Th）/他在一个基本的水平热年代学方法，并使用这些进步，以扩大范围的热历史相关的问题和问题，研究人员可以解决。研究锆石中的辐射损伤-He扩散系数关系和锆石中的辐射损伤退火动力学将有助于细化锆石（U-Th）/He系统的温度敏感性。这项研究将推进我们的知识的损伤扩散率的关系，通过逐步加热扩散实验斯里兰卡锆石颗粒的损伤范围内，目前只有一个单一的数据点存在。对一系列具有广泛辐射损伤的锆石颗粒进行的拉曼光谱测量将与热退火实验相结合，以提供有关锆石损伤退火过程的新动力学。锆石（U-Th）/He深时热年代学的进展将有助于通过热历史模拟来限制美国大陆中部新元古代折返的时间和幅度。这些结果将被用来评估现有的地球动力学模型的形成的大不整合面，其中每一个预测不同的时间和规模的侵蚀，从而提供深入了解大气-生物圈-岩石圈的相互作用在deep-time。这个奖项反映了NSF的法定使命，并已被认为是值得支持的评估使用基金会的智力价值和更广泛的影响审查标准。

Low-temperature thermochronology focuses on understanding the thermal histories of rocks in the upper ~10 km of Earth's crust. The suite of thermochronologic techniques has become essential for understanding the timing and rates of rock uplift and erosion in active or geologically young orogenic belts. This project focuses on a particularly promising and emerging area of research in deep-time (i.e. Precambrian) thermal histories. Deep-time thermochronology can be used to constrain the multiple phases of heating and cooling that have occurred over time spans of 100-1000 million years. This project will examine the timing and magnitude of erosion that created the Neoproterozoic-Cambrian Great Unconformity in the midcontinent U.S. with zircon (uranium-thorium)/helium thermochronology. The erosion constraints obtained as part of this project will serve as crucial inputs for investigations of atmosphere-biosphere-lithosphere feedbacks that relate estimates of erosion to 1) the disassembly of the supercontinent Rodinia, 2) potential triggers for snowball Earth glaciations, and 3) the Cambrian explosion in biodiversity. The project will also seek to further refine the temperature sensitivity of the zircon (uranium-thorium)/helium thermochronometer. The project incorporates an outreach and education plan that seeks to instill an appreciation for the concept of deep-time among undergraduates and the public through the use of a world-class resource available at the University of Illinois: the Rare Book and Manuscript Library. This library houses an extensive collection of rare geologic books and manuscripts dating back to the Enlightenment, which will be utilized in exhibits and incorporated into geology courses. These activities will impart a cultural knowledge of the concept of geologic time, foster a deeper appreciation for how Earth scientists think, and allow undergraduate students to engage with pre-modern primary literature to provide historical context and target fundamental questions of their science.This project focuses on advancing deep-time zircon (U-Th)/He thermochronologic methods at a fundamental level and uses these advancements to expand the range of thermal history related problems and questions that researchers can address. Investigations of the radiation damage-He diffusivity relationship in zircon and the kinetics for radiation damage annealing in zircon will help refine the temperature sensitivity of the zircon (U-Th)/He system. This research will advance our knowledge of the damage-diffusivity relationship via step-heating diffusion experiments on Sri Lankan zircon grains over a damage range for which currently only a single data point exists. Raman spectroscopy measurements from a suite of zircon grains with a wide range of radiation damage will be combined with thermal annealing experiments to provide new kinetics on the process of damage annealing in zircon. The advances in zircon (U-Th)/He deep-time thermochronology will help constrain the timing and magnitude of Neoproterozoic exhumation in the midcontinent U.S. through thermal history modeling. These results will be used to assess existing geodynamic models for the formation of the Great Unconformity, each of which predicts a different timing and magnitude of erosion, and thus provide insight into atmosphere-biosphere-lithosphere interactions in deep-time.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.