A review of studies on the magmatism at Southwest Indian Ridge from petrological and geochemical perspectives

The Southwest Indian Ridge (SWIR), as an ultraslow spreading ridge, has attracted great attentions from the geo-society of the world in the past three decades due to its unique morphology, crustal architecture, crustal accretion mode, volcanism, hydrothermal activities and deep mantle processes. This paper is devoted to the recent research progress on the petrology and geochemistry of basalt,gabbro and mantle peridotite collected from the SWIR. The geochemical data well revealed the variations of the whole ridge and ridge segments. Based on the data mentioned above, we described and discussed the main factors, which control the geochemical variations, magma supply and crustal accretion. In the oblique spreading ridge segment of 9°～16°E, the tectonics-dominated ocean ridge spreading patterns resulted in the wider oceanic crust accretion zone with significant geochemical anomalies; in the 50°～51°E ridge segment, strong volcanic activities occur, and its genetic mechanism includes different points of view, such as the interaction between the Crozet hotspot and SWIR, the micro hotspot, and the remelting of the residual mantle left behind by the former melting events. The latest research about the Longqi hydrothermal area (～ 49.7° E) suggests that the hydrothermal circulation is closely related to the development of detachment faults, and the maximum depth of hydrothermal circulation may reach 6 km below the Moho boundary. Therefore, it is suggested that the future study be strengthened in such issues as the mantle heterogeneity in different spatial scales, the tectonic-magmatic processes in the ridge system, ridge-plume interaction, and the seafloor hydrothermal activity and deposits.