Collaborative Research: Growth, preservation, and modification of Neoarchean to Paleoproterozoic crust, an example from the Wyoming province, Montana

合作研究：新太古代到古元古代地壳的生长、保存和改造，以蒙大拿州怀俄明州为例

• 批准号: 1854390
• 负责人: Jeffrey Vervoort
• 金额: $ 20.62万
• 依托单位: Washington State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-07-01 至 2025-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1854390&HistoricalAwards=false
• 关键词: Collaborative; Research; Growth; preservation; modification

Earth's continental crust is thought to have formed over discrete intervals of geologic time, where particular geologic processes resulted in enhanced crust formation and growth. These time intervals in the Precambrian also reflect a transition to modern plate tectonic processes, resulting in collision and assembly of smaller crustal fragments into continents and supercontinents. Rocks at the northwest margin of the Wyoming province in southwestern Montana provide a record of these processes during formation of the North American continent. This project will utilize an integrated approach by applying petrologic, geochemical, and geochronologic tools to establish relative contributions of crustal growth versus subsequent modification by tectonic processes. The major outcomes of this work will be a better understanding of the balance between crustal preservation and growth during continental assembly. This project will promote teaching and training by supporting graduate and undergraduate research, and results of this study will be incorporated into undergraduate class field trips and laboratory curricula. Infrastructure for research and education will be enhanced through the development and refinement of new geochronological techniques, and by providing training for students in state-of-the-art analytical equipment. New age data from this project will be integrated into current Montana state geologic mapping efforts to better interpret the overall ages of rock units and structural relationships. Outreach efforts will include presenting informal science talks for students and faculty from schools nationwide that conduct summer field courses in southwest Montana.Two intervals in the Neoarchean and Paleoproterozoic represent major periods in the growth and assembly of North America as well as continents worldwide. These periods have been inferred to correspond to times of enhanced production of continental crust. This project will examine the processes that have operated during these time intervals to produce new continental crust as well as the processes operating to rework and assemble this crust. The northwest margin of the Wyoming province in southwestern Montana is an ideal natural laboratory for this study because it is comprised of a diverse suite of metasedimentary garnet-bearing lithologies that are amenable to Pressure-temperature-time studies, as well as containing interlayered meta-igneous rocks that are poorly dated. The proposed work will apply an integrated approach of metamorphic phase equilibria and geochronology of Neoarchean to Paleoproterozoic rocks in the Laramide basement-cored uplifts of the Montana Metasedimentary Terrane to establish relative crustal growth versus modification during these time intervals. Data collected will determine the conditions, timing, duration, and spatial extent of magmatism and metamorphism through metamorphic phase equilibria, Uranium-Lead (U-Pb) geo- and thermochronology of zircon, monazite, and titanite, Hafnium (Hf) and Neodymium (Nd) isotopic analysis of zircon and monazite, and Lutetium-Hafnium/Samarium-Neodymium (Lu-Hf/Sm-Nd) dating of garnet. This integration of tools will provide temporal resolution magmatic and metamorphic histories and directly constrain the growth and modification history of the northwestern Wyoming province.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.

地球的大陆地壳被认为是在不连续的地质时间间隔内形成的，其中特定的地质过程导致了地壳形成和生长的增强。前寒武纪的这些时间间隔也反映了向现代板块构造过程的过渡，导致较小的地壳碎片碰撞并组装成大陆和超大陆。蒙大拿州西南部怀俄明州西北边缘的岩石记录了北美大陆形成过程中的这些过程。该项目将采用综合方法，通过应用岩石学、地球化学和地质年代学工具来确定地壳生长与随后构造过程改变的相对贡献。这项工作的主要成果将是更好地理解大陆组装过程中地壳保存和生长之间的平衡。该项目将通过支持研究生和本科生的研究来促进教学和培训，研究结果将纳入本科生课堂实地考察和实验室课程。将通过开发和完善新的地质年代学技术以及为学生提供最先进的分析设备培训来加强研究和教育基础设施。该项目的新年龄数据将整合到当前蒙大拿州地质测绘工作中，以更好地解释岩石单元的整体年龄和结构关系。推广工作将包括为全国学校的学生和教师举办非正式的科学讲座，这些学校在蒙大拿州西南部开展夏季实地课程。新太古代和古元古代的两个时期代表了北美以及世界各地大陆生长和聚集的主要时期。这些时期被推断对应于大陆地壳生产增强的时期。该项目将研究在这些时间间隔内产生新大陆地壳的过程以及改造和组装该地壳的过程。蒙大拿州西南部怀俄明州西北边缘是这项研究的理想天然实验室，因为它由多种变沉积石榴石岩性组成，适合压力-温度-时间研究，并且包含层间变质岩。年代不清的火成岩。拟议的工作将应用蒙大拿州变沉积地体拉拉米德基底核隆起中新太古代至古元古代岩石变质相平衡和地质年代学的综合方法，以确定这些时间间隔内的相对地壳生长与改变。收集的数据将通过变质相平衡、锆石、独居石、钛矿、铪 (Hf) 和钕的铀铅 (U-Pb) 地质和热年代学来确定岩浆作用和变质作用的条件、时间、持续时间和空间范围。 Nd) 锆石和独居石以及镥铪/钐钕的同位素分析石榴石的（Lu-Hf/Sm-Nd）测年。这种工具的集成将提供时间分辨率的岩浆和变质历史，并直接限制怀俄明州西北部的增长和改造历史。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进行评估，被认为值得支持标准。