Collaborative Research: Brittle-plastic deformation, fluid-rock interaction, and extensional reactivation along Laramide thrust faults in the Sangre de Cristo Mountains, Colorado

合作研究：科罗拉多州桑格雷德克里斯托山脉拉拉米德逆冲断层沿线的脆塑性变形、流体-岩石相互作用和伸展再活动

• 批准号: 2115745
• 负责人: Jeffrey Rahl
• 金额: $ 5.57万
• 依托单位: Washington and Lee University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-08-01 至 2025-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2115745&HistoricalAwards=false
• 关键词: Collaborative; Research; Brittle; plastic; deformation

This collaborative project investigates the deformation history of structures involved in formation of the Rocky Mountains and Rio Grande rift in southern Colorado. Through detailed fieldwork and laboratory analyses, the investigators will evaluate the timing and directions of motion along fault zones and the role of fluids in weakening these zones and facilitating tectonic activity. These results will help geoscientists better understand how rock strength affects fundamental mountain-building processes. This project will directly support thesis work for three Colorado State University graduate students and three Washington and Lee University undergraduate students, who will disseminate research results via publications and conference presentations. The study area in the Sangre de Cristo Mountains borders Great Sand Dunes National Park, which receives over half a million visitors each year, and the investigators will communicate research results with the park geologist to help provide additional geological context for educational outreach. This project will also support three years of an interdisciplinary student-led research seminar on the Sangre de Cristo Mountains within the Colorado State University Department of Geosciences. This seminar will involve at least 15 students (graduate and undergraduate) and 7 faculty members from across the Department, exposing students to a highly interdisciplinary approach to research. The project area in the Sangre de Cristo Mountains exposes some of the deepest Laramide and Rio Grande rift structural levels in the Rocky Mountain region, offering a rare opportunity to investigate deformation near the brittle-plastic transition. The investigators hypothesize that fluid-rock interactions weakened faults in this region, allowing contractional deformation to take place at relatively low stresses during the Laramide orogeny and extensional reactivation to occur on structures not optimally oriented for failure during development of the Rio Grande rift. Widespread shortening across the Laramide orogen may have been facilitated by fluid-related weakening, and extensional reactivation of thrust faults may represent a fundamental component of orogenic collapse. The investigators will test their hypotheses using a multidisciplinary research approach that includes geologic mapping, microstructural analysis, electron backscatter diffraction, Fourier transform infrared spectroscopy, stable isotope analysis, fluid inclusion analysis, geochemistry, and geo/thermochronology. Data generated in this project will provide key constraints on the stresses, temperatures, deformation mechanisms, and fluid involvement associated with intraplate shortening near the strongest part of the crust. This research will also shed light on the relations between Laramide contraction and Rio Grande rift extension and the role of shear zone geometry and rheology on extensional reactivation, providing a framework for understanding extensional reactivation of thrusts in other orogens.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.

该协作项目调查了与科罗拉多州南部的落基山和里奥格兰德裂谷形成的结构的变形历史。通过详细的现场工作和实验室分析，研究人员将评估沿断层区域运动的时间和方向，以及流体在削弱这些区域并促进构造活动中的作用。 这些结果将有助于地球科学家更好地了解岩石力量如何影响基本的山区建设过程。该项目将直接支持三名科罗拉多州立大学研究生以及三名华盛顿大学和李大学本科生的论文工作，他们将通过出版物和会议演讲来传播研究结果。 Sangre de Cristo山脉的研究区域与大沙丘国家公园接壤，该公园每年接待超过半百万的游客，调查人员将与公园地质学家交流研究结果，以帮助为教育外展提供其他地质环境。该项目还将支持科罗拉多州立大学地球科学系内的Sangre de Cristo山上的跨学科学生主导的研究研讨会。该研讨会将涉及至少15名学生（研究生和本科生）和来自部门的7位教职员工，使学生接受了一种高度跨学科的研究方法。 Sangre de Cristo山脉的项目区域暴露了落基山地区的一些最深的Laramide和Rio Grande Rift的结构水平，为研究脆性塑料过渡附近的变形提供了难得的机会。研究者假设流体岩石相互作用削弱了该区域的断层，从而使收缩变形在拉拉米德造山运动期间相对较低的应力下发生，并且在里约热内卢赖特（Rio Grande Rift）开发过程中未达到最佳失败的结构上发生了相对较低的应力。流体相关的弱化可能促进了整个Laramide造山基因的广泛缩短，推力断层的扩展重新激活可能代表了造山造成的基本组成部分。研究人员将使用多学科研究方法测试其假设，该方法包括地质映射，微结构分析，电子反向衍射，傅立叶变换红外光谱，稳定的同位素分析，流体包容性分析，地球化学分析，地球化学和地理/热量系统。该项目中产生的数据将对与地壳最强部分附近的压力，温度，变形机制和流体受累相关的关键限制。这项研究还将揭示Laramide收缩与Rio Grande Rift扩展之间的关系，以及剪切区的几何形状和流变性在扩展重新激活中的作用，为理解其他Orogens中推力的扩展重新激活提供了一个框架。该奖项是NSF的法定任务，反映了通过评估的构成群体的支持者，这表明了该奖项的构成群体的依据，并依靠构成了宗旨。