Collaborative Research: Effect of Contrasting Structural and Compositional Inheritances on the Development of Rifting Margins

在整个地球历史上，作为地球基本板块构造演化的一部分，大陆一直在分裂和重组。大陆如何在裂谷过程中分裂被认为是由构成岩石圈的地壳和地幔的固有结构和成分变化预先确定的，并且很可能继承自以前的构造事件。了解大陆分裂的类型为能源和矿产资源的勘探以及了解与这些过程相关的地质灾害提供了基础信息。地质观测经常支持这样一个事实，即这些继承是裂谷构造发育的关键参数，但这些继承在裂谷过程中发挥作用的程度尚不清楚。该项目研究了大陆岩石圈的可变组成和继承的地质构造的存在如何影响裂陷过程。一种多学科的方法将采用地质和地球物理观测来描述岩石圈地壳和地幔的遗传特征。这些观测结果将被整合到数值模型中，以模拟数百万年来岩石圈的延伸变形。该项目的结果将从根本上推进对岩石圈尺度变形过程的理解，并影响构造地质学、计算地球科学以及潜在的化石燃料群落。在更广泛的影响下，该项目支持德克萨斯州立大学（主要为西班牙裔服务的机构）的一名早期职业女性研究员，并将招募一名硕士生直接参与研究。被动边缘定义了大约一半的地球海岸线，并成为近几十年来众多研究的焦点。虽然对裂陷过程的认识有了很大的提高，但关于继承条件对扩展岩石圈局部化过程的影响的基本问题仍然存在。多项研究表明，构造、成分和热演化是裂谷构造发育的关键参数。然而，它们在分手过程中发挥多大作用尚不清楚。本项目将解决继承性强烈影响裂陷过程的假设，并可以解释：1)变形初始阶段的应变分布，2)裂陷过程中的减薄机制，以及3)导致挖掘和/或海洋地壳形成的机制。为了验证这一假设，将对构造和成分继承进行数值裂谷实验。从二维地震和三维结构观测中获得的定向结构被参数化。为了解释在大陆岩石圈中观察到的成分的自然变化，这些非均质性被赋予了多矿物组成。为了约束模型，将使用多学科方法，结合：1)地质和地球物理数据分析，2)使用双矿物流变学系统探索数值模拟实验的影响，以及3)使用2D和3D数值模型对加拿大东北部边缘进行案例研究。这种方法将允许通过独立地改变遗产的组成、分布和方向来获得大量关于裂谷演化的定量信息。研究结果将有助于加深对大陆分裂过程中应变分布、局部化过程和变形机制的认识，并将不同继承类型下裂陷过程的动态演化可视化。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。

Throughout Earth's history continents have broken apart and reassembled as part of the fundamental plate tectonic evolution of the planet. How continents break apart by rifting processes is thought to be predefined by inherent structural and compositional variability of Earth's crust and mantle that make up the lithosphere and is likely inherited from previous tectonic events. Understanding the style of continental breakup provides fundamental information for the exploration for energy and mineral resources and to understanding the geologic hazards associated with these processes. Geological observations often support the fact that these inheritances are key parameters in the development of rift structures but the extent to which these inheritances play a role during the rifting process remain unclear. This project investigates how the variable composition of continental lithosphere and the presence of inherited geological structures affect rifting processes. A multi-disciplinary approach will employ geological and geophysical observations to characterize inheritances in the crust and mantle of the lithosphere. These observations will be integrated into numerical models that simulate the deformation of the lithosphere over millions of years by extension. The results of this project will fundamentally advance the understanding of lithospheric scale deformation processes and impact structural geology, computational geosciences and potentially the fossil fuel communities. Under broader impacts the project supports an early career female researcher at Texas State University, a primarily Hispanic-serving institution, and a master student will be recruited to participate directly in the research.Passive margins define about half of the Earth's coastlines and have been the focus of numerous studies in recent decades. While understanding of rifting processes has greatly improved, fundamental questions remain on the effects of inherited conditions on localization processes in extending lithosphere. Multiple studies suggest that structural, compositional and thermal inheritances are key parameters in the development of rift structures. However, the extent to which they play a role during breakup is still unclear. This project will address the hypothesis that inheritances strongly affect rifting processes and can explain: 1) the distribution of strain during the initial phase of deformation, 2) the mechanism of thinning during the rifting process, and 3) the mechanism leading to the exhumation and/or the formation of oceanic crust. To test this hypothesis numerical rifting experiments will be run with both structural and compositional inheritances. Inheritances are parameterized as oriented fabrics obtained from 2D seismic and 3D structural observations. A polymineralic composition is assigned to these heterogeneities in order to account for the natural variation in compositions observed in the continental lithosphere. In order to constrain the models, a multidisciplinary approach will be used that combines: 1) the analysis of geological and geophysical data, 2) a systematic exploration of the effects of numerical modeling experiments using a bimineralic rheology, and 3) a case study of the Northeastern Canadian margin with 2D and 3D numerical models. This approach will allow for a large amount of quantitative information on rift evolution to be acquired by independently varying the composition, distribution and orientation of inheritances. Results will help improve understanding of strain distribution, localization processes and mechanisms of deformation during continental breakup, and visualize the dynamic evolution of rifting processes depending on the type of inheritances.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.