洋中脊玄武岩（MORB）成分变化主要受三个因素控制：地幔潜能温度、地幔组成和洋脊扩张速率。但哪种因素起主导作用，主控因素在不同洋脊是否一样，存在争议。另外，对全球MORB Hf-Nd同位素耦合/解耦的空间尺度和成因认识也不清楚。中大西洋洋脊33-35ºN之间OH-1和OH-3洋脊下地幔潜能温度、洋脊扩张速率相同（Niu等，2001），但玄武岩微量元素成分变化几乎涵盖全球MORB变化范围。因此是从Sr-Nd-Pb-Hf同位素角度研究地幔组成与MORB成分变化联系的理想场所，也是从区域上研究Hf-Nd同位素耦合/解耦的理想场所。本项目拟对OH-1和OH-3 MORB样品进行密集的Sr-Nd-Pb-Hf同位素分析，揭示其沿着洋脊的变化及其与主量元素和不相容元素比值的关系，进一步探讨地幔组成与MORB组分的联系、富集地幔组分成因和Hf-Nd相关性，对于深入理解MORB成因和地幔动力学具有重要意义。

Mantle temperature variation, plate spreading rate and mantle composition have been considered to be the fundamental variables that control the compositions of mid-ocean ridge basalts (MORB). However, there is debate over which variable exerts the major control and whether it is the same under different ridges. Moreover, it remains unclear whether the Hf-Nd isotopic coupling/decoupling exists on a global or local scale and its origin. Along the portion of the Mid-Atlantic Ridge (MAR) between the Oceanographer (35ºN) and Hayes (33ºN) transforms, the mantle potential temperature and the plate spreading rate are the same, but the compositions of the basalts vary drastically (almost covering the global MORB ranges, Niu et al., 2001). Therefore, it is an ideal place to study the relationship between mantle composition and MORB geochemical variations from Sr-Nd-Pb-Hf isotopic perspectives, and to examine MORB Hf-Nd isotopic correlation at a specific portion of ridge. We employ a Sr-Nd-Pb-Hf approach to unravel the along-ridge isotopic variations and their relationships with major elements and abundances and ratios of incompatible elements. These results allow us to further evaluate the mantle compositional control on MORB geochemical variations, the origin of enriched mantle component and Hf-Nd correlation from Sr-Nd-Pb-Hf perspectives. This has bearing on understanding the origin of MORB and mantle geodynamics.