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

在地球的整个历史中，作为地球基本板块构造演化的一部分，大陆已经分裂并重新组装。 大陆如何通过裂谷过程分裂被认为是由组成岩石圈的地壳和地幔的固有结构和成分变化所预先确定的，并且可能继承自以前的构造事件。了解大陆裂解的方式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本信息。地质观测常常支持这样一个事实，即这些继承性是裂谷构造发展的关键参数，但这些继承性在裂谷过程中发挥作用的程度仍不清楚。本项目研究大陆岩石圈的可变组成和继承的地质结构的存在如何影响裂谷过程。一个多学科的方法将采用地质和地球物理观测的特点，在地壳和岩石圈地幔的继承。这些观测结果将被整合到数值模型中，模拟岩石圈在数百万年内的变形。 该项目的成果将从根本上推进对岩石圈尺度变形过程的理解，并影响结构地质学、计算地球科学和潜在的化石燃料社区。在更广泛的影响下，该项目支持德克萨斯州立大学的一名早期职业女性研究员，这是一所主要为西班牙裔服务的机构，一名硕士生将被招募直接参与研究。虽然裂谷过程的理解有了很大的提高，基本问题仍然是在扩展岩石圈的本地化过程中的继承条件的影响。多项研究表明，构造、成分和热继承性是裂谷构造发育的关键参数。然而，他们在分手过程中发挥作用的程度仍不清楚。该项目将探讨遗传对裂谷过程有很大影响的假设，并能解释：1）变形初始阶段的应变分布，2）裂谷过程中减薄的机制，3）导致折返和/或洋壳形成的机制。为了验证这一假设，将进行构造和成分遗传的数值裂谷实验。继承性被参数化为从2D地震和3D构造观测获得的定向组构。一个多矿物组合物被分配到这些异质性，以解释在大陆岩石圈中观察到的组合物的自然变化。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的分析，2）系统探索的影响，使用双矿物流变学的数值模拟实验，和3）加拿大东北部边缘的案例研究与二维和三维数值模型。这种方法将允许大量的定量信息裂谷演化获得独立的变化的组成，分布和方向的继承。研究结果将有助于提高对大陆分裂过程中应变分布、局部化过程和变形机制的理解，并可视化断裂过程的动态演化，这取决于继承的类型。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.