The Mystery Deepens: Anomalously Fast Speed of the Indian Lithospheric Plate - A Review

ABSTRACT During certain time windows of the late Cretaceous and early Tertiary the Indian plate travelled northward from deep south with exceptionally fast speed reaching around 15–18 to ~22 cm/yr. This is indeed intriguing and enigmatic because velocities of all other major tectonic plates, in comparison, do not exceed ~7–8 cm/yr and hence the high mobility of the Indian plate remains somewhat mysterious. This study discusses the various efforts carried out during the past four decades, which are aimed at understanding the processes/forces behind this rapid drift of India. On the basis of marine magnetic survey, deep drilling and numerical models, a number of potential causes have been put forward. Some of the important observations that emerged from these studies are, (i) delineation of multi-phase subduction systems within the India-Asia collision corridor, (ii) occurrence of upwelling of more than one mantle plumes and their push force, (iii) anti-correlated velocities of the Indian and African plates and their coupling with the Reunion mantle plume, and (iv) role of mantle plume in the initiation of subduction or convergent margin that implies initiation of the plate tectonics itself. These studies suggest a number of potential causes that could impart the observed high acceleration to the Indian plate. These include lithospheric thinning and geophysical/geochemical characteristics of the Indian plate, weakening of the litho-asthenospheric coupling and the coupling of mantle plume and double subduction. During the past decade, continued addition of concepts and ideas that negate/compliment/supplement preceding studies, comprehend the forces responsible for India’s rapid drift. It is significant to note that most of these suggestions have come up, in quick succession, thus making the unfoldment of this research highly engrossing and interesting.