Investigation of the triple oxygen isotope systematics of shales in the Precambrian

页岩是一种主要的沉积岩类型，它记录了地壳的组成及其风化作用。由于风化过程中水分大量过剩，页岩氧同位素值反映了水与岩石相互作用的同位素值和风化温度。利用三氧同位素（17O/16O对比18O/16O）对主要沉积岩类型、页岩和伴生成岩二氧化硅进行分类学研究，以期深入了解地球早期的古环境和风化条件。他收集的页岩覆盖了35亿年，跨越了主要的雪球地球冰川和温室时期，大氧化事件，新元古代海洋多细胞生命的出现，以及陆地生命的出现。作为教育部分的一部分，这个项目将支持一名研究生。作为这项努力的延伸，这位研究者将于2020年在旧金山举行的美国地球物理会议上主持一个为期一天的研讨会，他将邀请从事这一主题工作的同事，以及那些对前寒武纪精确微量分析和稀有同位素方法的出现感兴趣的人。此外，他还将开发一套17O标准，用于跨实验室校准delta 18O和delta 17O值的大范围，并将其提供给社区，用于分析沉积和其他材料。该项目将：1)使用研究者新建的高精度17O提取线，对地质历史上的页岩进行测量，这些页岩此前已被表征为δ 18O、钛同位素和化学成分；2)描述成熟岩石圈、演化水圈和（或）大陆陆地范围增加的长期和特定地质间隔的三氧趋势；3)研究页岩和锆石中的石英随时间的三重氧特征；4)建立水圈-地壳耦合演化的地球化学盒模型，并添加额外的17O输入参数，这将允许解决先前基于他们和其他实验室的测量结果与太古宙较热环境与低三角洲18O水圈相关的争议。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Shale is a major sedimentary rock type that records the composition of the Earth's crust and its weathering. As the process of weathering proceeds with a great excess of water, the oxygen isotope value in shales reflects the isotopic value of water interacting with the rock and the temperature of weathering. Using triple oxygen isotopes (17O/16O versus 18O/16O) systematics in the main sedimentary rock type, shale and associated diagenetic silica, the investigator proposes to gain insight into paleoenvironmental and weathering conditions during early Earth's history. His collection of shales covers 3.5 billion years and spans the major snowball Earth glacial and greenhouse episodes, the Great Oxidation Event, the Neoproterozoic appearance of multicellular life in oceans, and the appearance of life on land. As part of the educational component, this project will support a graduate student. As an outreach of this effort, the investigator will lead a one-day workshop at the American Geophysical meeting in San Francisco in 2020, to which he will invite colleagues working on this topic, as well as those interested in the advent of precise microanalytical and rare isotope methods for the Precambrian. He will additionally develop a set of standards for 17O that span a large range in delta 18O and delta 17O values for cross-laboratory calibration purposes and make it available to the community for analysis of sedimentary and other materials.The project will: 1) make measurements, using the investigator's newly constructed high-precision 17O extraction line, of a collection of shales across geologic history that has been previously characterized for delta 18O, Titanium isotopes, and chemical composition; 2) describe long-term and geological interval-specific, triple oxygen trends of maturing lithosphere, evolving hydrosphere and/or increasing continental subaerial extent; 3) examine triple oxygen signatures of quartz within shales and zircons through time, and 4) build a geochemical box model of coupled hydrosphere-crustal evolution with additional 17O input parameters that will permit resolution of previous controversies related to hotter environments in the Archean versus low delta 18O hydrosphere based on their measurements and those generated by other laboratories.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.