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

最近对海洋核心复合体(OCC)的观察是耐人寻味的。当断层不断滑动并最终将下地壳和地幔岩石剥离到海底时，OCCS就形成了。OCCS不仅通过发现深层岩石来一瞥地球的地幔，而且它们通常有与之相关的热液喷口，这些喷口拥有大型生态系统。当第一次被发现时，OCCS被认为主要形成在缓慢扩张的大洋中脊部分的末端，那里的岩浆供应很少。然而，在远离扩散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，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。该项目将制作一个三维力学模型，以了解大洋中脊OCCS形成的控制因素。首要目标是了解断层在洋盆形成和演化中的作用。该项目将招募本科生参与这项研究，重点是确定传统上在科学界代表性较低的群体的参与者。将制作解释模型和模型结果的电影，并将在研究生课程中使用，并改编用于K-12学校。在缓慢扩展的大洋中脊，浸水频率和断层类型高度不同，并在某种程度上相互关联。然而，我们对这种相关性和其他控制断裂样式的因素背后的机制的了解仍然不完整。该项目的目标是建立确定断裂类型的机制，以响应缓慢扩展海脊的空间和时间变化的岩脉频率，并量化该机制对断层润滑过程和扩张中心的岩浆挤压和底侵的敏感性。该项目建议通过扩展现有的二维(2D)方法来开发一种三维(3D)建模方法，该方法已成功地解释了大洋中脊横轴部分的主要形态和结构特征。全三维数值模型考虑了堤防和断层变化引起的沿轴机械载荷。此外，该建模方法还将考虑影响断层类型的其他重要因素，如形成在断层表面的摩擦弱矿物的润滑作用。四套数值实验将按复杂程度递增的顺序进行。

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.