Collaborative Research: Tectono-magmatic Controls on the Origin and Evolution of Mid-Ocean Ridge Segmentation at Slow-to-Intermediate Spreading Rates - Top down or bottom up

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The Earth's surface is divided into a collection of rigid tectonic plates that migrate and interact in response to convection in the underlying mantle. Mid-ocean ridges, the largest volcanic system on Earth, represent plate boundaries where tectonic plates move apart from one another. Ridges are divided into discrete spreading segments, separated by zones of faulting that accommodate varying degrees of strike-slip motion and extension. This project will use state-of-the-art 3-D numerical models to quantify the processes that lead to the formation of these spreading segments and the style of deformation within the offset zones that separate them. The science supported by this research will bolster STEM education in its relevance to a basic understanding of plate tectonics and geohazards. The PIs will give presentations in local K-12 schools and work with high school teachers to create demonstrations that meet specific milestones in physics curricula. The computational code developed through this project will be made available to anyone via the BitBucket public repository. Finally, the international research team with expertise in geology, geophysics, and high-performance computing will ensure that the two graduate students at Boston Colelge and the Univeristy of Hawaii will develop the cross-disciplinary skills needed by the next generation of Earth scientists. Mid-ocean ridge segmentation is the first-order manifestation of plate-tectonics and yet, we still have only a preliminary understanding of the causes for the different forms of segment offsets. This gap in knowledge is largely a result of the fact that the vast majority of prior studies have focused on either lithospheric (top down) or mantle/magma (bottom up) controls, but not both. This study will develop 3-D geodynamic models of a segmented mid-ocean ridge to explore how (i) the fraction of magmatically accommodated extension, M, (ii) segment offset length, and (iii) lithosphere thickness variations, and (iv) fault rheology determine whether the offset between two segments takes the form of a localized transform fault or a zone of more diffuse and variable deformation characteristic of non-transform offsets. Model predictions will be tested and the parameter space refined based on analyses of topography and fault characteristics, including measurements of M, at archetypal transforms and non-transform offsets. Finally, the study will investigate the origin and evolution of mid-ocean ridge segmentation using models that allow the location of magma injection to evolve dynamically and to influence whether adjacent offsets take the form of a non-transform offset or evolves into a transform fault.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.