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

职业：精炼锆石 (U-Th)/He 深时热年代学以约束新元古代热历史

• 批准号: 1848013
• 负责人: William Guenthner
• 金额: $ 53.09万
• 依托单位: University of Illinois at Urbana-Champaign
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-06-01 至 2024-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1848013&HistoricalAwards=false
• 关键词: CAREER; Refining; zircon; Th; He

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.

低温热年代学侧重于了解地壳上层约 10 公里岩石的热历史。这套热年代学技术对于了解活跃或地质年轻的造山带中岩石隆起和侵蚀的时间和速率至关重要。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。深时热年代学可用于约束 100-10 亿年时间跨度内发生的多个加热和冷却阶段。该项目将利用锆石（铀-钍）/氦热年代学研究在美国中部大陆造成新元古代-寒武纪大不整合面的侵蚀的时间和程度。作为该项目的一部分获得的侵蚀约束将作为大气-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) 超大陆罗迪尼亚的解体、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联系起来。该项目还将寻求进一步改进锆石（铀钍）/氦热计的温度灵敏度。该项目包含一项外展和教育计划，旨在通过使用伊利诺伊大学的世界级资源：善本和手稿图书馆，向本科生和公众灌输对深度时间概念的欣赏。该图书馆藏有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 地址。研究锆石中辐射损伤-He 扩散率关系以及锆石中辐射损伤退火动力学将有助于完善锆石 (U-Th)/He 系统的温度敏感性。这项研究将通过对斯里兰卡锆石颗粒在目前仅存在单个数据点的损伤范围内进行逐步加热扩散实验，增进我们对损伤扩散关系的了解。对一系列具有广泛辐射损伤的锆石晶粒进行拉曼光谱测量，将与热退火实验相结合，为锆石损伤退火过程提供新的动力学。锆石 (U-Th)/He 深时热年代学的进展将有助于通过热历史模型来限制美国中部大陆新元古代折返的时间和幅度。这些结果将用于评估大不整合面形成的现有地球动力学模型，每个模型都预测不同的侵蚀时间和程度，从而提供对大气-生物圈-岩石圈在深部相互作用的深入了解。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Zircon (U-Th)/He thermochronology of Grand Canyon resolves 1250 Ma unroofing at the Great Unconformity and <20 Ma canyon carving

大峡谷锆石 (U-Th)/He 热年代学解析了大不整合面 1250 Ma 的揭顶和 <20 Ma 的峡谷雕刻

• DOI: 10.1130/g48699.1
• 发表时间: 2021
• 期刊: Geology
• 影响因子: 5.8
• 作者: Thurston, Olivia G.;Guenthner, William R.;Karlstrom, Karl E.;Ricketts, Jason W.;Heizler, Matthew T.;Timmons, J. Michael
• 通讯作者: Timmons, J. Michael

Implementation of an Alpha Damage Annealing Model for Zircon (U‐Th)/He Thermochronology With Comparison to a Zircon Fission Track Annealing Model

锆石 (U–Th)/He 热年代学的 Alpha 损伤退火模型的实现与锆石裂变径迹退火模型的比较

• DOI: 10.1029/2019gc008757
• 发表时间: 2021
• 期刊: Geosystems
• 作者: Guenthner, William R.