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.

低温热量学的重点是理解地壳上部约10 km中岩石的热历史。热量技术技术的套件对于理解活性或地质型造山带的岩石隆起和侵蚀的时机和速率已成为必不可少的。该项目着重于深度（即前寒武纪）热历史的特别有前途和新兴的研究领域。深度热量学可用于限制随着时间的推移跨度为100-1亿年的加热和冷却的多个阶段。该项目将检查腐蚀的时机和幅度，从而在美国中部大陆与锆石（铀thorium）/氦热量体产生了新元古生代 - 夏布里的巨大不整合性。作为该项目的一部分获得的侵蚀约束将是对大气生物圈 - 偏度反馈的研究至关重要的投入，将侵蚀的估计值与1）超大陆Rodinia的拆卸，2）潜在的雪球地球冰球的潜在触发因素，以及3）杀菌剂的生物爆炸性。该项目还将寻求进一步完善锆石（铀thorium）/氦气热量器的温度灵敏度。该项目纳入了一项宣传和教育计划，该计划旨在通过使用伊利诺伊大学的世界一流资源来灌输对本科生和公众之间深度时间概念的赞赏：稀有书籍和手稿图书馆。该图书馆收藏了广泛的稀有地质书籍和手稿，可以追溯到启蒙运动，这些书籍将用于展览中，并将其纳入地质课程中。这些活动将传授对地质时代概念的文化知识，促进对地球科学家的思考方式的更深入的认识，并允许本科生与前现代的主要文献互动，以提供历史上下文和针对其科学的基本问题。该项目侧重于促进深度时间的氧化锆（U-Th）和热门研究的范围，以促进这些问题的研究，以扩展这些问题的研究范围，以扩展这些问题的范围，以扩展这些范围的范围，以扩展这些范围的范围，以提高这些范围的范围。 地址。对辐射损伤的研究-HE扩散关系与锆石退火的动力学中的扩散关系将有助于提高锆石（U-TH）/HE系统的温度灵敏度。这项研究将通过对斯里兰卡锆石晶粒进行逐步加热扩散实验的损害扩散关系的了解，这是目前仅存在一个数据点的损伤范围。来自具有广泛辐射损伤的锆石晶粒套件的拉曼光谱测量将与热退火实验结合使用，以提供有关锆石损伤退火过程的新动力学。锆石（U-TH）/HE Deep-Time热合体的进步将有助于通过热历史建模来限制美国中部美国中部新元古代挖掘的时间和幅度。这些结果将用于评估现有的地质动力学模型，以形成巨大的不整合性，每个模型都预测了侵蚀的时间和大小的不同，因此在深度时间内对大气 - 双层 - 双层层相互作用进行了深入的了解。该奖项反映了NSF的法定任务，并通过使用基金会的智力效果和广泛的评估来进行评估。

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.