Constraints on the lithospheric structure and tectonics of Archean Dharwar Craton, southern India from geophysical and geological data: Evidence for modified lithosphere

Abstract

• Mantle plume activities eroded the lithospheric keel of the Archean Dharwar Craton. • Small-scale convection destabilized and promoted erosion of lithospheric mantle. • SCLM is metasomatized as indicated by low S-wave velocities (Vs = 4.1-4.4 km/s). • Effective distance of mantle plume activity is ∼1500 km from the source region. Cratons are the stable portions of the continents for at least the past two billion years. Their longevity is generally attributed to their thick, cold, rheologically strong and chemically depleted subcrustal mantle lithosphere. The lithosphere achieved both buoyancy and strength by relatively low thermal regime and compositional differences due to dehydration, presence of melt-depleted peridotites and low iron content. Low temperature of the mantle lithosphere leads to high viscosity, which prevents deformation and thus preserves the cratonic root. However, significant modifications/erosion of the lithospheric root is observed for some cratons from different parts of the globe. The present paper discusses some aspects of lithospheric modification of the Archean Dharwar Craton, southern India. Southern India is a mosaic of several Archean cratonic blocks, the Western and Eastern Dharwar cratons, and Southern Granulite Terrain. It has experienced several tectonic and magmatic events, including mafic dykes of various periods since Paleoproterozoic. The Dharwar Craton was accreted with the Karwar and Coorg blocks on the west and Eastern Ghats and Nallamalai fold belts on the east during the Proterozoic. The Cuddapah, Bhima and Kaladgi basins were formed during the Proterozoic period. A 1.1 Ga kimberlite magmatism and 550 Ma East-African orogen are other important geodynamic events of the region. The western and eastern continental margins, together with the Deccan Large Igneous Province, one of the world's largest igneous provinces, were formed due to mantle plume activities during 130-65 Ma. 2500 km long Himalayan Mountain chain was formed during ∼55 Ma. Active and passive seismic, magnetotelluric, gravity, xenolith and elevation data complimented with geological data were used to understand the lithospheric structure. Subduction, collision and mantle plume activities, which are main processes for crustal evolution are also found responsible for lithospheric destruction in the region. The detached subducted slabs from various geodynamic activities of the region might have led to rheological weakening of the subcontinental lithospheric mantle and thereby craton modification/erosion in the southern India. Mantle plume activities are responsible for epeirogenic uplift and lithospheric thinning in the southern India.