The Northern Central Indian Ridge: Geology and tectonics of fracture zones-dominated spreading ridge segments

Multi-beam and single-beam bathymetric, gravity and magnetic data, across seven ridge segments (length varying between 37 and 84 km), offset by six transform discontinuities (ranging in dislocation length between 48 and 344 km) of the Northern Central Indian Ridge (NCIR) were collected. Four Transform Faults (TF, viz. Sealark, Vityaz, Ehrlich and Vema) have been mapped in detail; while studies on geological, biological and water sampling were carried out at the last three transform faults. The ridge segments are characterized by along-axis depth variation: deepening at segment ends and shallowing at the centre. Both the ridge axis and TF areas are complex with intra- and inter-segmental morphotectonic and magnetic variations. Basalts collected from axial valley, Ridge-Transform Intersection (RTI) and from near-axis seamount, exhibit pillow and columnar structures. Samples from the RTI yielded ferromanganese crust, nodules and intensely bioturbated calcareous sediments hosting nannoplanktons. The characteristics of the RTI, axial valley and transform and the presence of neo-volcanic zones along ridge-normal profiles suggest predominance of tectonomagmatic activities in the Vityaz and Vema regions. In the Sealark region, tectonic activities dominate.