Upper Mantle Structure beneath the Mid-Ocean Ridges in Indian Ocean: Insights from the Seismic Tomography Models

Abstract

Mid-ocean ridges (MORs) are critical regions for plate tectonics, mantle upwelling, magma output and oceanic crust accretion. Understanding the upper mantle structure beneath MORs is essential for unraveling the geodynamic processes driving ridge evolution. However, the existing research work are mostly focused on a specific ridge segment, few knowledge about the 3D structure of the sub-ridge upper mantle has been revealed. This study focused on the Indian Ocean ridge system, utilizing upper mantle tomography data to analyze both low-velocity and highvelocity anomalies beneath MORs. The tomographic features of upper mantle beneath Indian Ocean varies a lot vertically, with the shallow layer showing the ridge activity, the middle layer indicating plume conduits, and the deep layer exhibiting rather homogeneous transition zone. The lateral extent of shallow low-velocity zones (LVZs) is related to spreading rate, with wider LVZs for faster spreading ridges. Large transform faults usually truncate the LVZs along ridge axis. Beneath the LVZs high-velocity anomalies can be observed for most of the ridge segments, the size of which seems decrease with increasing spreading rates. The study presents an overall image of the upper mantle for Indian Ocean, especially for the ridge systems. It provides direct evidence for the ridge evolution and its connection to the deep earth. The newly picked-up high-velocity anomalies under LVZ may require further confirmation, and whether it is the shadow of relic subducted slabs need more detail seismic investigations.

Keywords

Indian Ocean MORs / seismic tomography / upper mantle structure / low velocity anomaly / spreading rate / geodynamics / geophysics

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