Fully three-dimensional numerical models for along-axis variations in magmatic and tectonic processes at slow-spreading mid-ocean ridges

缓慢扩张的洋中脊岩浆和构造过程沿轴变化的全三维数值模型

基本信息

批准号：
1658072
负责人：
Eunseo Choi
金额：
$ 17.93万
依托单位：
University of Memphis
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2017
资助国家：
美国
起止时间：
2017-03-15 至 2020-02-29
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1658072&HistoricalAwards=false
关键词：
Fully three dimensional numerical models

项目摘要

The recent observations of oceanic core complexes (OCCs) are intriguing. OCCs are formed when faults keep slipping and eventually exhume lower crust and mantle rocks onto the seafloor. OCCs not only provide a glimpse into Earth's mantle by uncovering deep-seated rocks, but they commonly have hydrothermal vents associated with them which host large ecosystems. When first discovered, OCCs were assumed to form primarily near the ends of slow-spreading mid-ocean ridge segments where magma supply is low. However, they also have been found at locations far from spreading segment ends. Moreover, in some place the formation of OCCs alternates with normal seafloor spreading which produces short-lived faults. It is unclear what controls the alternating faulting styles. This project will produce a three-dimensional mechanical model to understand the controls on the formation of OCCs at mid-ocean ridges. The overarching goal is to understand the role of faulting in the formation and evolution of the ocean basins. The project will recruit undergraduate students to participate in the research with a priority on identifying participants from groups traditionally underrepresented in the sciences. Movies will be generated explaining the model and model results and will be used in graduate courses and adapted for use in K-12 schools.Diking frequencies and faulting styles are highly variable at slow-spreading mid-ocean ridges and correlated with each other to some degree. However, our understanding of the mechanism behind the correlation and other factors controlling faulting styles is still incomplete. The objectives of this project are to establish the mechanism that determines faulting styles in response to spatially and temporally varying diking frequencies at slow-spreading ridges and to quantify the sensitivity of the mechanism to fault-lubricating processes and magma extrusion and under-plating at spreading centers. The project proposes to develop a three-dimensional (3D) modeling approach by extending an existing two-dimensional (2D) method that has been successful in explaining the main morphological and structural features in across-axis sections of mid-ocean ridges in terms of diking frequencies. The fully 3D numerical models incorporate the along-axis mechanical loading arising from variability in diking and faulting. Furthermore, the modeling method will consider other important factors affecting faulting styles such as lubrication effects of frictionally weak minerals forming on fault surfaces. Four suites of numerical experiments will be conducted in the order of increasing complexity.

最近对海洋核心复合体（OCC）的观察很有趣。 OCC 是在断层不断滑动并最终将下地壳和地幔岩石挖掘到海底时形成的。 OCC 不仅可以通过揭示深层岩石来了解地幔，而且它们通常还具有与其相关的热液喷口，这些喷口拥有大型生态系统。首次发现时，OCC 被认为主要形成于缓慢扩张的洋中脊部分的末端附近，那里的岩浆供应量较低。然而，它们也在远离扩展段末端的位置被发现。此外，在某些地方，OCC 的形成与正常的海底扩张交替出现，从而产生短暂的断层。目前尚不清楚是什么控制着交替的断层样式。该项目将建立一个三维力学模型，以了解洋中脊 OCC 形成的控制。首要目标是了解断层作用在洋盆形成和演化中的作用。该项目将招募本科生参与研究，并优先从传统上在科学领域代表性不足的群体中寻找参与者。将生成解释模型和模型结果的视频，并将用于研究生课程并改编为 K-12 学校使用。在缓慢扩张的洋中脊处，堤坝频率和断层类型变化很大，并且在某些情况下彼此相关。程度。然而，我们对相关性背后的机制和控制断层样式的其他因素的理解仍然不完整。该项目的目标是建立一种机制，确定断层类型，以响应缓慢扩张的山脊上时空变化的堤防频率，并量化该机制对断层润滑过程以及扩张时岩浆挤出和底镀的敏感性。中心。该项目建议通过扩展现有的二维 (2D) 方法来开发三维 (3D) 建模方法，该方法已成功解释洋中脊跨轴部分的主要形态和结构特征：筑堤频率。全 3D 数值模型包含因筑堤和断层的变化而产生的沿轴机械载荷。此外，建模方法将考虑影响断层类型的其他重要因素，例如断层表面上形成的摩擦弱矿物的润滑作用。将按照复杂性增加的顺序进行四组数值实验。