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，记录了地壳的组成及其风化作用。由于风化过程是在水大量过剩的情况下进行的，页岩中的氧同位素值反映了与岩石相互作用的水的同位素值和风化温度。使用三重氧同位素（17 O/16 O与18 O/16 O）系统学在主要的沉积岩类型，页岩和相关的成岩二氧化硅，研究人员提出，以深入了解古环境和风化条件在早期地球的历史。他收集的页岩涵盖了35亿年，跨越了主要的雪球地球冰川和温室事件，大氧化事件，新元古代海洋中多细胞生命的出现，以及陆地上生命的出现。作为教育部分的一部分，该项目将支持一名研究生。作为这一努力的推广，研究人员将于2020年在旧金山弗朗西斯科举行的美国地球物理会议上举办为期一天的研讨会，他将邀请从事这一主题的同事，以及那些对精确微量分析和稀有同位素方法的出现感兴趣的人。此外，他亦会制定一套17 O的标准，涵盖18 O和17 O的三角洲值，以供跨实验室校正之用，并提供予社会人士作沉积物和其他物质的分析。1）使用研究人员新建造的高精度17 O提取线进行测量，地质历史上的页岩集合，其特征在于三角洲18 O、钛同位素和化学成分; 2）描述成熟岩石圈、演化水圈和/或增加大陆陆上范围的长期和地质间隔特定的三重氧趋势; 3）检查页岩和锆石中石英随时间的三重氧特征，4）建立耦合水圈-地壳演化与额外的17 O输入参数，这将允许解决以前的争议有关的更热的环境在太古代与低三角洲18 O水圈的基础上，他们的测量和其他实验室产生的。这个奖项反映了NSF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.