Slow Spreading Ridges of the Indian Ocean: An Overview of Marine Geophysical Investigations

Sparse and non-availability of high resolution geophysical data hindered the delineation of accurate morphology, structural configuration, tectonism and spreading history of Carlsberg Ridge (CR) and Central Indian Ridges (CIR) in the Indian Ocean between Owen fracture zone at about 10N, and the Rodriguez Triple Junction at ~25S. Analysis of available multibeam bathymetry, magnetic, gravity, seabed sampling on the ridge crest, and selected water column data suggest that even with similar slow spreading history the segmentation significantly differ over the CR and CIR ridge systems. Topography, magnetic and gravity signatures indicate non-transform discontinuity over CR and suggest that it has relatively slower spreading history than CIR. Magmatic and less magmatic events characterize CR and CIR respectively and well defined oceanic core complex (OCC) are confined only to segments of the CIR. The mantle Bouguer anomaly signatures over the ridges suggest crustal accretion and pattern of localized magnetic anomalies indicate zones of high magnetization coinciding with the axial volcanic ridges. Geophysical investigations / thermal plumes in the water column, have brought out two new hydrothermal vents over CR and one vent indication over the CIR. The analysis of the tectonic and magmatic character of the CR and CIR based on the available high resolution data suggests that both these slow spreading ridge sections have the potential to host high temperature active hydrothermal vents and need to be investigated by AUV and ROV experiments to identify the causative mechanism of these vents and their association with unique seafloor and sub-seafloor deep-sea ecosystems. These ridges hold great promise of mineral resources.