Relationship of the Central Indian Ridge segmentation with the evolution of the Rodrigues Triple Junction for the past 8 Myr

Located near 25 degrees 33'S, 70 degrees 00'E, the Rodrigues Triple Junctio n is the joining point of the intermediate-spreading Southeast Indian and C entral Indian Ridges with the ultraslow spreading Southwest Indian Ridge. B athymetric data and magnetic anomalies are used to analyze the relationship between the evolution of the Central Indian Ridge segmentation and the evo lution of the Rodrigues Triple Junction for the past 8 Myr. The Central Ind ian Ridge domain exhibits a complex morphotectonic pattern dominated by rid ge-normal and oblique bathymetric lows interpreted as the off-axis traces o f axial discontinuities. The short-lived nontransform discontinuities as we ll as the segments that lengthen or shorten along the ridge axis reveal tha t the Central Indian Ridge segmentation is unstable near the Rodrigues Trip le Junction. The combined study of the Central Indian Ridge and Southeast I ndian Ridge domains shows that the triple junction evolves between two mode s: a continuous mode where the Central Indian Ridge and Southeast Indian Ri dge axes are joined and a discontinuous mode where the two ridge axes are o ffset. Owing to spreading asymmetry, and differences in axis direction or i n lengthening rates of the Central Indian and Southeast Indian ridges, the continuous mode is unstable and evolves rapidly (<2 Myr) into a discontinuo us mode. This last one is more stable and can evolve into a continuous mode only through the formation of a new Central Indian Ridge segment, which ta kes place facing the northern Southeast Indian Ridge segment. The evolution of the Rodrigues Triple Junction configuration and the evolution of the Ce ntral Indian Ridge segmentation are thus closely related.