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至24个月的研究。该计划的奖项提供了联合研究的机会，并利用国外独特或互补的设施、专业知识和实验条件。该奖项将支持Eric L.Mittelstaedt博士与法国巴黎物理研究所(IPGP)的Anne Davavle博士合作的为期24个月的研究奖学金。全球大洋中脊系统的分段不断变化，旧分段消亡，新分段不断创建。最大的脊不连续表现为一级为转换断层，二级为重叠扩展中心(OSCS)或很少重叠或不重叠的非转换偏移距(NTOS)。沿东太平洋隆起、中大西洋海脊、胡安德·富卡海脊和加拉帕戈斯扩展中心的观测表明，脊轴分段模式随扩展速度和热点附近的不同而不同。快速扩展和魔术般坚固的海脊通常表现出快速的区段迁移和大量的OSC。相比之下，缓慢扩张和神奇般差的山脊通常具有长期存在的山脊分段，具有非常慢的迁移率，并倾向于NTO和较小的转换断层而不是OSC。这项研究主要集中在了解控制这些不同风格的脊线分割的过程。以前的数值研究、实验室研究和理论研究都试图理解作为岩石圈变形或地幔流动模式的函数的山脊分段的形成。然而，目前还缺乏一套完整的脊线分割理论。我们使用联合实验室和三维数值方法来研究脊线分割的机理。实验室实验包括对具有脆性-延展性的流体混合物施加拉伸，从下面加热，在表面冷却。数值模型使用有限元程序Citcom，我们最近实现了伪塑性流变学和简化的熔化和熔体传输。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，以更好地了解脊线分段的产生和演化。

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.