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 other, and the cause of the super-mobility of the Indian subcontinent is an unresolved problem. As the lithospheric plates and the Sub-lithospheric mantle form the two key elements of plate tectonic movement, the thermal characteristics of the three constituent plates of Gondwanaland, i.e. the Indian, African and Australian landmasses, have been compared in this study. It has been clearly shown that the mean surface heat flow values (QsBAR) in those Gondwana terrains of India which remained 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 Australia 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 mantle beneath the Indian Peninsula is not hotter or less viscous than that beneath the African and Australian shields. These results and inferences evidently imply that the thermal regime and the other related parameters of the continental lithosphere do not contribute to the mobility of the plates to which it is attached, that the rapid movement of the Indian landmass is not coupled with the thermal characteristics of its lithosphere, and that the drag force, which the present studies have shown to be insignificant, would not have been lower on the base of the Indian lithosphere than beneath the African and Australian landmasses. Accordingly, the earlier reported postulate that the high velocity of the Indian landmass is due to its thin and hot continental lithosphere and less viscous upper mantle is not valid. The paleo-reconstruction indicates the existence of the Reunion and Kerguelen plumes, one on each side of the Indian landmass. It is likely that these plumes created, in the sub-lithospheric mantle, favourable conditions which worked together with forces that resulted from slab pull and ridge push to give a high velocity to the Indian landmass.