Collaborative Research: Integrating Fluorspar Ages and Geophysical Models to Constrain the Timing and Mechanisms of the Collapse of the Cordillera in SW North America

合作研究：整合萤石年龄和地球物理模型来约束北美西南部科迪勒拉山脉塌陷的时间和机制

• 批准号: 2317871
• 负责人: Paul Tomascak
• 金额: $ 9.09万
• 依托单位: SUNY College at Oswego
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-09-01 至 2027-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2317871&HistoricalAwards=false
• 关键词: Collaborative; Research; Integrating; Fluorspar; Ages

About 60 million years ago Southwestern North America was a mountain belt with the length of the Himalayas and height of the Andes. These mountains collapsed under their own load starting about 30 million years ago, ending in the classic Basin and Range province that exists in the region today. The geological history of this collapsing mountain belt is also connected with the formation of deposits of minerals critically necessary for the security and maintenance of the economic well-being of the United States. The research team will test the hypothesis that fluids flowing through the crust were key to the collapse through the dating of fluorspar deposits that are geographically associated. These deposits themselves are a critical mineral resource. The research will use innovative dating methods to estimate the time of formation of the fluorite and associated minerals and compare this with the time of collapse of the highlands. The timing for the emplacement of these deposits will provide key information for proposed numerical simulations of the processes. Previous geophysical studies have provided three-dimensional imaging of the Earth’s interior for the region that will also be used to inform and test the numerical simulations, and these geophysical studies will be updated to better aid the simulations. The computer simulations will also contribute to a better understanding of the sources and magnitudes of tectonic forces responsible for earthquakes in the region, contributing to a better seismic hazard assessment. The project involves a collaborative plan to engage a diverse undergraduate and graduate student population with all components of laboratory, computational, and field work. Outstanding questions remain about the thermomechanical processes involved in the extensional collapse of the North American Southwest Cordillera, including the evolution of thermal input, crustal fluids and melts, topographic change, and plate tectonic and mantle flow evolution. Low upper mantle seismic wave speeds, together with active volcanism, are insufficient to predict rapid lithospheric strain rates in the southwestern US. Instead, in addition to the slow upper mantle wave speeds and volcanism, the lithosphere is characterized by abundant geothermal waters, enriched in F and 3He (indicating mantle fluid sources), which predicts rapid lithospheric strain. Belts of fluorspar deposits, which are associated with highly extended zones, are therefore likely to be precipitates of paleofluids emplaced during times of rapid transtensional crustal strain. The proposed work will test this hypothesis by using U/Pb and (U–Th)/He dating combined with a high-resolution time-dependent thermomechanical model. Furthermore, 40Ar/39Ar dating of associated sericite and alunite deposits will provide validation and confidence in the fluorite dating methods. Thermomechanical model outputs will be compared with geologic, thermochronologic, sedimentologic, and geophysical observations. The proposed thermochemical modeling will 1) quantify the causes and consequences of the topographic changes of the study area by modeling the collapse of the Nevada-plano and Arizona-plano; 2) identify the mechanisms for lithospheric weakening, including the role of thermal and magmatic evolution; 3) provide direct tectonic context for deformation and seismic hazards within the modern Basin and Range Province; and 4) integrate the latest seismic results from the Earthscope project by incorporating seismic, thermal, and compositional information of the lithosphere-asthenosphere system. Metamorphic core complex formation is hypothesized to be linked to collapse of highlands, but to date no 3-D models have directly addressed the effects of body forces set up by realistic topography. Methods developed for this proposal are poised to address the physics of the development of the core complexes as well as the structural evolution of the Basin and Range in the context of the inferred timing of rheological weakening informed by fluorspar dating. The novel approach to dating fluorspar, together with the integrated thermomechanical modeling plan, can be applied to other regions of the world where fluorspar deposits are associated with extensional zones. The proposed work involves a collaborative plan to integrate a diverse undergraduate and graduate student population with all components of laboratory, computational, and field work. The collaboration involves colleagues and students from Suffolk Community College, Kingsborough Community College, SUNY Oswego, Columbia University, and Stony Brook University. The integrated work will engage under-represented minority undergraduate students and will train the next generation of geoscientists in an exciting interdisciplinary effort. Students will be engaged every summer in training seminars, and will be involved in laboratory work, computational geodynamic modeling using Python and Jupyter Notebooks, and field preparation, training, and field work. Outreach efforts will culminate in short courses at GSA and AGU on communicating science to a broader audience. This collaborative work explores the cutting-edge linkage between critical mineral formation and the 3-D evolution of the dynamics of Southwest Cordillera.This project is jointly funded by the Frontier Research in Earth Systems Program and the Division of Earth Sciences to support projects that increase research capabilities, capacity and infrastructure at a wide variety of institution types, as outlined in the GEO EMBRACE DCL.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.

大约6000万年前，北美西南部是一条山脉带，有喜马拉雅山脉的长度和安第斯山脉的高度。这些山脉在自己的负荷下坍塌了大约3000万年前开始，最终形成了今天存在于该地区的经典盆地和山脉省。这个崩塌的山带的地质历史也与矿藏的形成有关，这些矿藏对美国的安全和维持经济福祉至关重要。研究小组将通过对地理上相关的萤石矿床进行测年，来验证流经地壳的流体是崩塌的关键这一假设。这些矿床本身就是一种重要的矿产资源。这项研究将使用创新的测年方法来估计萤石和伴生矿物的形成时间，并将其与高地崩塌的时间进行比较。这些沉积物就位的时间将为提出的过程数值模拟提供关键信息。以前的地球物理研究已经为该地区提供了地球内部的三维图像，这些图像也将用于通知和测试数值模拟，这些地球物理研究将被更新以更好地帮助模拟。计算机模拟还将有助于更好地了解导致该地区地震的构造力的来源和震级，从而有助于更好地进行地震危险性评估。该项目涉及一个合作计划，让不同的本科生和研究生群体参与实验室、计算和实地工作的所有组成部分。关于北美西南科迪勒拉伸展性崩塌的热力学过程，包括热输入演化、地壳流体和熔体演化、地形变化、板块构造和地幔流演化，仍有许多悬而未决的问题。低上地幔地震波速度，加上活火山活动，不足以预测美国西南部岩石圈的快速应变速率。相反，除了上地幔波速缓慢和火山活动外，岩石圈的特征是丰富的地热水，富含F和3He（表明地幔流体来源），这预示着岩石圈的快速应变。因此，与高度伸展带相关的萤石矿床带很可能是在地壳快速张拉应变时期沉积的古流体的沉淀。提出的工作将通过使用U/Pb和(U - th)/He定年以及高分辨率时间相关的热力学模型来验证这一假设。此外，伴生绢云母和明矾石矿床的40Ar/39Ar定年将为萤石定年方法提供验证和信心。热力学模型输出将与地质、热年代学、沉积学和地球物理观测结果进行比较。提出的热化学模型将1)通过模拟内华达-平原和亚利桑那-平原的崩塌来量化研究区域地形变化的原因和后果；2)确定岩石圈弱化的机制，包括热演化和岩浆演化的作用；3)为现代盆地和岭省的变形和地震灾害提供了直接的构造背景；4)结合岩石圈-软流圈系统的地震、热、成分信息，整合Earthscope项目的最新地震成果。据推测，变质岩心复合体的形成与高地的崩塌有关，但迄今为止，还没有三维模型能直接解决现实地形所产生的身体力的影响。为本建议开发的方法准备在通过萤石测年推断流变减弱时间的背景下，解决核心复合体发展的物理问题以及盆地和山脉的结构演化。这种测定萤石年代的新方法，连同综合热力学建模计划，可应用于世界上其他与伸展带有关的萤石矿床地区。提议的工作包括一个协作计划，将不同的本科生和研究生群体与实验室、计算和实地工作的所有组成部分结合起来。这项合作涉及来自萨福克社区学院、金斯堡社区学院、纽约州立大学奥斯威戈分校、哥伦比亚大学和石溪大学的同事和学生。这项综合工作将吸引代表性不足的少数民族本科生，并将在令人兴奋的跨学科努力中培养下一代地球科学家。学生将参加每年夏天的培训研讨会，并将参与实验室工作，使用Python和Jupyter notebook进行计算地球动力学建模，以及实地准备，培训和实地工作。推广工作将在GSA和AGU的短期课程中达到高潮，向更广泛的受众传播科学。这项合作工作探索了关键矿物形成和西南科迪勒拉动力学的三维演化之间的前沿联系。该项目由地球系统前沿研究计划和地球科学部联合资助，以支持在各种机构类型中增加研究能力、能力和基础设施的项目，如GEO EMBRACE DCL所述。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。