Plume signatures on- and off-axis of segment 3-1 between 10°S and 11°S, Central Indian Ridge

Abstract:

In Central Indian Ridge, segment 3-1 between 10°S and 11°S is bounded by well developed fracture zone in northern end of the segment of which middle valley is displaced 109 km-long with right-lateral sense. In the segment, ridge-parallel abyssal hills are mostly recognized at the northern section while the disturbed flank fabrics are limited in the south inside corner where ocean core complex is located. Spreading center represents a narrow and shallow valley floor at the middle of the segment but becomes wide and deep at the ends of segment. The shallow valley in middle of the segment is indicative of abundant magmatic upwelling. The ocean core complex in the southern end of the segment rises to ~1000 m from the valley floor and extends tens km perpendicular to the axial ridge, displaying the gentle dome structure with corrugations well traced. In the axial valley, light scattering anomalies are observed at both the middle and southern end of the segment but the significant methane anomalies are merely detected at the southern end of segment. At off-axis, the ocean core complex reveals both light scattering and methane anomalies. Considering the methane anomalies over the core complex where mantle rocks expose by long detachment faults, plumes at this region seems to be derived by tectonic and amagmatic processes. Whereas the particulate anomalies with few methane anomaly in the middle of segment implies plumes appears to be created by magmatism.