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

[077579 . 20]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至24个月的研究。该计划的奖励为联合研究提供了机会，并利用独特或互补的设施、专业知识和国外的实验条件。该奖项将支持Eric L. Mittelstaedt博士与Anne Davaille博士在法国巴黎环球体质研究所（IPGP）开展为期24个月的研究。全球洋中脊系统的分割是不断变化的，旧的部分消失，新的部分产生。最大的脊面不连续在一级表现为变换断层，在二级表现为重叠扩展中心（OSCs）或很少重叠或没有重叠的非变换偏移（NTOs）。沿东太平洋隆起、大西洋中脊、胡安德富卡脊和加拉帕戈斯扩展中心的观测表明，脊轴切分模式随扩展速率和靠近热点而变化。快速扩张和岩浆坚固的山脊通常表现为快速分段迁移和大量的osc。相比之下，缓慢扩张和岩浆性差的山脊通常具有长寿命的山脊分割，迁移速度非常慢，有利于NTOs和小的转换断层到osc。本研究主要集中于了解控制这些不同类型脊分割的过程。以前单独的数值研究、实验室研究和理论研究都试图将洋脊分割的形成理解为岩石圈变形或地幔流动模式的函数。然而，目前还缺乏完整的脊分割理论。我们使用联合实验室和三维数值方法来研究脊分割的力学。实验室实验包括对具有脆性-延性的流体混合物施加拉伸，从下面加热并在表面冷却。数值模型采用我们最近实现的拟塑性流变和简化的熔体和熔体输运的有限元代码Citcom。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产生和演化。

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.