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

最近对海洋核复合体（OCCs）的观测很有趣。当断层不断滑动并最终将下地壳和地幔岩石挖掘到海底时，OCCs就形成了。OCCs不仅通过揭示深层岩石提供了对地幔的一瞥，而且它们通常有与之相关的热液喷口，这些喷口承载着大型生态系统。最初发现OCCs时，人们认为OCCs主要形成于缓慢扩张的洋中脊段的末端，那里的岩浆供应较低。然而，在远离伸展节段末端的位置也发现了它们。此外，在某些地方，OCCs的形成与正常的海底扩张交替发生，从而产生短暂的断层。目前还不清楚是什么控制了交替的断层样式。该项目将产生一个三维力学模型，以了解海洋中脊OCCs形成的控制因素。总体目标是了解断裂在海洋盆地形成和演化中的作用。该项目将招募本科生参与研究，优先考虑从传统上在科学领域代表性不足的群体中确定参与者。将生成解释模型和模型结果的电影，并将用于研究生课程和K-12学校的改编使用。在缓慢扩张的洋中脊，基底频率和断层样式变化很大，并在一定程度上相互关联。然而，我们对相关关系和控制断裂样式的其他因素背后的机制的认识仍然不完整。本项目的目标是建立一种机制，根据缓慢扩展的脊的空间和时间变化来确定断层样式，并量化该机制对断层润滑过程和扩展中心岩浆挤压和下镀的敏感性。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，该方法已经成功地解释了海洋中脊跨轴部分的主要形态和结构特征。全三维数值模型包含了沿轴的力学载荷，这些载荷是由岩壁和断层的变化引起的。此外，建模方法还将考虑其他影响断层样式的重要因素，如在断层表面形成的摩擦弱矿物的润滑作用。四组数值实验将按复杂度递增的顺序进行。

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.