A COMPARISON OF HEAT-FLOW FROM THE GONDWANA CONTINENTS WITH VELOCITIES OF GONDWANA PLATES - GEODYNAMIC IMPLICATIONS

The velocities of the lithospheric plates generally differ from each o ther, and the cause of the super-mobility of the Indian subcontinent i s an unresolved problem. As the lithospheric plates and the Sub-lithos pheric mantle form the two key elements of plate tectonic movement, th e thermal characteristics of the three constituent plates of Gondwanal and, i.e. the Indian, African and Australian landmasses, have been com pared in this study. It has been clearly shown that the mean surface h eat flow values (QsBAR) in those Gondwana terrains of India which rema ined unaffected by tectonic and igneous activity during the last 150 m .y., i.e. after the break-up of Gondwanaland, are either equal to or ( mostly) lower by 5-22 mW m-2 than those in similar terrains of Austral ia and even the immobile African continent, and that QsBAR values for the terrains of these landmasses which were affected by such activity during the last 150 m.y. are uniformly equal. It is inferred that the Indian lithosphere is neither hotter nor thinner than that beneath the above-mentioned continents, and that the sub-lithospheric upper mantl e beneath the Indian Peninsula is not hotter or less viscous than that beneath the African and Australian shields. These results and inferen ces evidently imply that the thermal regime and the other related para meters of the continental lithosphere do not contribute to the mobilit y of the plates to which it is attached, that the rapid movement of th e Indian landmass is not coupled with the thermal characteristics of i ts lithosphere, and that the drag force, which the present studies hav e shown to be insignificant, would not have been lower on the base of the Indian lithosphere than beneath the African and Australian landmas ses. Accordingly, the earlier reported postulate that the high velocit y of the Indian landmass is due to its thin and hot continental lithos phere and less viscous upper mantle is not valid. The paleo-reconstruc tion indicates the existence of the Reunion and Kerguelen plumes, one on each side of the Indian landmass. It is likely that these plumes cr eated, in the sub-lithospheric mantle, favourable conditions which wor ked together with forces that resulted from slab pull and ridge push t o give a high velocity to the Indian landmass.