International Research Fellowship Program: The Origin and Evolution of Mid-Ocean Ridge Segmentation at Normal and Hotspot Affected Ridges

国际研究奖学金计划使美国科学家和工程师能够在国外进行9到24个月的研究。 该计划的奖项提供了联合研究的机会，以及使用独特或互补的设施，专业知识和国外的实验条件。Mittelstaedt与法国巴黎地球仪物理研究所（IPGP）的Anne Davaille博士合作。 最大的脊不连续性表现为1阶转换故障和2阶重叠扩展中心（OSC）或非转换偏移很少或没有重叠（NTO）。 沿东太平洋海隆、中大西洋海隆、胡安·德富卡海隆和加拉帕戈斯扩张中心的沿着观测表明，海隆轴分割模式随扩张速度和热点的接近程度而变化。 快速扩张和岩浆作用强烈的海脊通常显示出快速的分段迁移和大量的OSC。 相比之下，缓慢扩张和岩浆贫乏的山脊通常具有长期的山脊分段，迁移速率非常缓慢，有利于NTO和小的转换断层到OSC。 这项研究主要集中在了解控制这些不同风格的脊分割的过程。 以往的数值、实验室和理论研究都试图了解洋脊分段的形成与岩石圈变形或地幔流动模式的关系。 然而，脊分割的整体理论是缺乏的。 我们使用联合实验室和3-D数值方法来研究脊分割的力学。 实验室实验包括对具有脆塑性行为的流体混合物施加拉伸，从下面加热并在表面冷却。数值模型使用有限元代码Citcom与我们最近实施的假塑性流变学和简化的熔化和熔体输送。 这些实验和模拟的结果将与现有的地球物理和地球化学数据进行比较，以更好地了解脊分段的创建和演变。

0757920MittelstaedtThe International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad.This award will support a twenty-four month research fellowship by Dr. Eric L. Mittelstaedt to work with Dr. Anne Davaille at Institut de Physique du Globe de Paris (IPGP) in France.Segmentation of the global mid-ocean ridge system is continually changing with old segments dying and new segments being created. The largest ridge discontinuities are manifest to 1st order as transform faults and to 2nd order as either overlapping spreading centers (OSCs) or non-transform offsets with little or no overlap (NTOs). Observations along the East Pacific Rise, the Mid-Atlantic Ridge, the Juan de Fuca Ridge and the Galapagos Spreading Center indicate that ridge axis segmentation patterns vary with spreading rate and proximity to a hotspot. Fast-spreading and magmatically-robust ridges generally display rapid segment migration and numerous OSCs. In contrast, slow-spreading and magmatically-poor ridges typically have long lived ridge segmentation with very slow migration rates and favor NTOs and small transform faults to OSCs. This research focuses primarily on understanding the processes which control these differing styles of ridge segmentation. Previous separate numerical, laboratory, and theoretical studies have attempted to understand the formation of ridge segmentation as a function of lithospheric deformation or mantle flow patterns. However, an overall theory of ridge segmentation is lacking. We use a joint laboratory and 3-D numerical approach to study the mechanics of ridge segmentation. The laboratory experiments involve imposing extension on a fluid mixture with brittle-ductile behavior, heated from below and cooled on the surface. The numerical models use the finite-element code Citcom with our recent implementation of pseudo-plastic rheology and simplified melting and melt transport. The results of these experiments and simulations will be compared to existing geophysical and geochemical data to provide a better understanding of the creation and evolution of ridge segmentation.