This study investigates the variations in mantle potential temperature and mantle Bouguer anomaly (MBA) along the South Mid-Atlantic Ridge (SMAR), aiming to understand the interaction of mid-ocean ridge (MOR) and mantle plume. The research focuses on the SMAR segments situated between 13°S and 25°S. Our findings indicate a positive correlation between mantle temperature and the depth at which initial melting takes place. This implies that higher mantle temperatures result in deeper initial partial melting depths. Moreover, there is a positive correlation between the degree of partial melting and the depth interval between the initial and final melting depths. This suggests that the extent of mantle melting in these SMAR regions is primarily controlled by decompression melting rather than the influence of increasing mantle temperature. As a result of the considerable distance of approximately 750 km between the SMAR and the Saint Helena plume, the range of mantle temperatures does not exhibit as much variation as that seen at the Reykjanes and Kolbeinsey ridges, which are influenced by the on-axis Iceland plume. The MBA values across the entire ridge segment (referred to as segment 2 in this study) are generally low, whereas the low MBA values are scattered along Segments 3–5. This observation suggests that the concentration of upwelling hot plume material is higher at the center of segment 2 compared to other ridge segments. Additionally, the gradient of MBA values along the SMAR segments between 13°S and 25°S indicates the presence of a large mantle domain (up to 700 km in length) that is influenced by the plume in the SMAR asthenosphere. The continuous variation in MBA between the Cardno Seamount group and segment 2 further suggests that this distinct mantle domain is associated with the Saint Helena mantle plume. Mantle preconditioning, as indicated by Yb/Nd and Nd/Nd systematic, reveals that the flow channels resembling schlieren between segments 4–5 and the Saint Helena plume may contribute to the influence of melt extraction and transform offsets on the propagation of plume material.

中文翻译：

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南大西洋中脊沿地幔位温和地幔布格异常变化：对脊和羽流相互作用的影响


本研究调查了南大西洋中脊（SMAR）沿线地幔位温和地幔布格异常（MBA）的变化，旨在了解大洋中脊（MOR）与地幔柱的相互作用。该研究重点关注位于南纬 13° 至 25° 之间的 SMAR 段。我们的研究结果表明地幔温度与初始熔化发生的深度之间呈正相关。这意味着更高的地幔温度会导致更深的初始部分熔化深度。此外，部分熔化程度与初始熔化深度和最终熔化深度之间的深度间隔呈正相关。这表明这些 SMAR 区域的地幔熔化程度主要受减压熔化控制，而不是地幔温度升高的影响。由于 SMAR 和圣赫勒拿地幔柱之间相距约 750 公里，地幔温度范围的变化并不像雷克雅内斯山脊和科尔宾塞山脊那样大，后者受到轴上冰岛的影响羽。整个山脊段（本研究中称为段 2）的 MBA 值通常较低，而低 MBA 值分散在段 3-5 上。这一观察结果表明，与其他山脊段相比，段 2 中心的上涌热羽流物质浓度更高。此外，13°S 和 25°S 之间 SMAR 段的 MBA 值梯度表明存在受 SMAR 软流圈羽流影响的大型地幔域（长达 700 公里）。 卡德诺海山群和第 2 段之间 MBA 的连续变化进一步表明，这个独特的地幔域与圣赫勒拿地幔柱有关。 Yb/Nd 和 Nd/Nd 系统表明，地幔预处理揭示了第 4-5 段和圣赫勒拿羽流之间类似纹影的流动通道可能有助于熔体提取和变换偏移对羽流物质传播的影响。