Geopotential imprints on the tectono-thermal evolution of the northwest Indian Ocean

Abstract

The study investigates the tectonic and lithospheric characteristics of the northwestern Indian Ocean, emphasizing tectonothermal parameters: Moho depth, Effective Elastic Thickness (Te), loading ratio (F), Depth to the Bottom of the Magnetic Sources (DBMS), and Geoid-to-Topography Ratio (GTR). Low to moderate Te values, moderate to high F values and low to moderate DBMS over aseismic ridges, such as the Laxmi and Laccadive Ridges, suggest dominant subsurface loading due to underplating and mantle magma intrusion. The Murray Ridge exhibits the DBMS close to the Moho, indicating a relatively warm lithosphere. The Carlsberg Ridge, as expected, shows a thin oceanic crust (~ 8 km Moho depth) and significant variations in Te and DBMS along its length. These reflect mantle upwelling, magmatic processes, and lithospheric stretching. Seamounts in the Arabian Basin likely formed due to ridge spreading and volcanic activity near the Carlsberg Ridge. The seamount chain in the East Somali Basin may have formed from magma rising beneath the moving African plate. The Chain Ridge separates oceanic lithospheres of varying ages, showing strong lithospheric support with localized thermal modifications and high GTR. Variations in GTR values depict compensation mechanisms, transitioning from shallow in the younger crust (< 30 Ma) to deeper in the older crust, driven by mantle dynamics and lithospheric processes. The relationship between crustal age and DBMS reveals two tectono-thermal events: one at 35 Ma, which may be associated with Indian-Eurasian collision processes; the other at 65 Ma, is related to Réunion hotspot activity formed that caused Deccan volcanism and underplating in the adjacent region.