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，大陆已经分裂并重新组合。大陆如何通过裂谷过程分裂被认为是由构成岩石圈的地壳和地幔固有的结构和成分变化预先定义的，很可能是从以前的构造事件中继承下来的。了解大陆裂解的类型，为能源和矿产资源的勘探以及了解与这些过程有关的地质灾害提供了基本信息。地质观察通常支持这样一个事实，即这些遗产是裂谷构造发展的关键参数，但这些遗产在裂谷过程中发挥的作用程度尚不清楚。该项目调查大陆岩石圈的不同组成和继承地质结构的存在如何影响裂谷作用。多学科方法将利用地质和地球物理观测来确定岩石圈地壳和地幔的继承性。这些观测将被整合到数值模型中，通过延伸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促进对岩石圈规模变形过程的理解，并对构造地质学、计算地球科学以及潜在的化石燃料社区产生影响。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，并将招募一名硕士研究生直接参与研究。被动边缘定义了地球约一半的海岸线，近几十年来一直是众多研究的重点。虽然对裂谷作用的了解已经有了很大的进步，但基本的问题仍然是遗传条件对岩石圈伸展的局部化过程的影响。多项研究表明，构造、成分和热继承是裂谷构造发育的关键参数。然而，他们在分手过程中发挥了多大作用仍不清楚。该项目将解决继承强烈影响裂谷作用的假设，并可以解释：1)变形初始阶段的应变分布，2)裂谷过程中的减薄机制，以及3)导致洋壳折返和/或形成的机制。为了验证这一假设，将进行具有结构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构造观测中获得的定向组构。为了解释大陆岩石圈中观察到的成分的自然变化，对这些不均质性赋予了多矿物成分。为了约束模型，将使用多学科方法，其中包括：1)地质和地球物理数据的分析；2)使用双矿物流变学系统地探索数值模拟实验的效果；3)使用2D和3D数值模型对加拿大东北边缘的案例进行研究。这一方法将允许通过独立地改变遗产的组成、分布和方向来获得关于裂谷演化的大量定量信息。结果将有助于更好地了解大陆解体期间的应变分布、本地化过程和变形机制，并根据遗产类型可视化裂谷过程的动态演变。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.