Collaborative Research: An integrated evaluation of lower crustal rheology and localization processes in plagioclase-rich rocks

合作研究：富含斜长石岩石下地壳流变学和定位过程的综合评价

• 批准号: 2123718
• 负责人: Basil Tikoff
• 金额: $ 26.77万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-05-01 至 2025-04-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2123718&HistoricalAwards=false
• 关键词: Collaborative; Research; integrated; evaluation; lower; Collaborative; Research; integrated; evaluation; lower

Earth’s crust deforms by different processes at different depths. The lower part of the crust is difficult to access in the field and is therefore less understood than the upper crust. Although earthquakes typically occur in the upper crust, the lower crust affects earthquake activity by transferring stress to shallower faults. Using a combination of field studies, laboratory analyses, and numerical models, this project will evaluate which processes allowed deformation to occur in narrow zones in the lower crust. This project will use an exposure of lower crustal deformation that at the surface in Québec, Canada, allowing us to directly study the rocks and deformational processes. In particular, the researchers will determine if interaction with shallower earthquake-causing faults in the upper crust is sufficient to explain the characteristics of this region, or if additional rock weakening processes play a fundamental role. This relationship between upper and lower crustal deformation is important to understand the earthquake cycle and related hazards. In addition, undergraduate students will participate in both the field and analytical portions of this project as part of a capstone class, gaining valuable exposure to the benefits of scientific collaboration between numerical modelers (theoreticians) and field geologists (empiricists).The field site selected for this project is the Morin Shear Zone in Québec, Canada. Its western portion exclusively deforms anorthositic rock. The large proportion of plagioclase in this rock means that it can be treated it as effectively a single phase and take advantage of the abundance of laboratory constraints on the mechanical behavior of plagioclase. This project is based on tight integration between constraints from the field and laboratory and numerical geodynamic modeling. Specific tasks will be to: 1) document shear zone deformation conditions, structure, and evolution from the field; 2) numerically model and predict strain gradients in the lower crust near a brittle fault, absent of any weakening processes; 3) report from the field evidence of microstructural or chemical changes that may affect rheology and weaken rocks; and 4) numerically evaluate the impact of any suspected weakening processes on shear zone geometry and structure. At the conclusion of this project, the researchers will have determined whether the observed shear zone results from deformation imposed by a brittle fault higher in the strike-slip system, or whether weakening mechanisms are necessary to cause the observed pattern. The project will also demonstrate the power of integrating field-based studies and numerical modeling studies in structural geology. Furthermore, this project will engage undergraduate students in research internships and in a non-field camp capstone experience. These students will have direct exposure to our combined observational and theoretical approaches, and will gain a better appreciation for the range of expertise and interests of current research in the geological sciences.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.

地球的地壳在不同深度处的不同过程变形。地壳的下部很难在田间进入，因此比上皮的理解少。尽管地震通常发生在上皮中，但下层地壳通过将应力转移到较浅的断层来影响地震活动。使用现场研究，实验室分析和数值模型的组合，该项目将评估哪些过程允许在下层地壳的狭窄区域中发生变形。该项目将使用较低的地壳变形的暴露，该变形在加拿大魁北克的地面上，使我们能够直接研究岩石和变形过程。特别是，研究人员将确定与较浅地震的上皮中的较浅的断层相互作用足以解释该地区的特征，或者其他岩石弱化的过程是否起着基本作用。上层和下地壳变形之间的这种关系对于了解地震周期和相关危害很重要。此外，本科生将作为顶峰类别的一部分参与该项目的领域和分析部分，从而获得价值暴露于数字建模者（理论上）与实地地质学家（经验家）之间科学合作的好处。为该项目选择的现场站点是加拿大魁北克的Morin剪切区。独家畸形的尖锐岩石。在这条岩石中，斜长石的很大比例意味着它可以被视为有效的单相，并利用实验室的丰富性在斜长石的机械行为上。该项目基于实验室与实验室的约束与数字地球动力学建模之间的紧密整合。特定的任务将是：1）文档剪切区变形条件，结构和田地的演变； 2）在脆性断层附近的下地壳中的数值模型并预测不存在任何弱过程的应变梯度； 3）从现场证据的报告中，微结构或化学变化可能影响流变学和弱岩石； 4）数值评估了任何可疑的过程对剪切区几何形状和结构的影响。在该项目的结论结束时，研究人员将确定观察到的剪切区是否是由于脆性断层在走滑系统中施加的变形而导致的，还是是否需要弱化机制来引起观察到的模式。该项目还将证明在结构地质学中整合基于现场的研究和数值建模研究的力量。此外，该项目将吸引本科生的研究实习和非场营地盖石体验。这些学生将直接接触我们的观察和理论方法，并将对当前研究中当前研究的专业知识和利益的范围获得更好的认识。该奖项反映了NSF的法定任务，并被认为是通过基金会的知识分子和更广泛的影响审查标准来通过评估来通过评估来获得的支持。