Could the Réunion plume have thinned the Indian craton?

Thick and highly viscous roots are the key to cratonic survival. Nevertheless, cratonic roots can be destroyed under certain geological scenarios. Eruption of mantle plumes underneath cratons can reduce root viscosity and thus make them more prone to deformation by mantle convection. It has been proposed that the Indian craton could have been thinned due to eruption of the Réunion plume underneath it at ca. 65 Ma. In this study, we constructed spherical time-dependent forward mantle convection models to investigate whether the Réunion plume eruption could have reduced the Indian craton thickness. Along with testing the effect of different strengths of craton and its surrounding asthenosphere, we examined the effect of temperature-dependent viscosity on craton deformation. Our results show that the plume-induced thermomechanical erosion could have reduced the Indian craton thickness by as much as ~130 km in the presence of temperature-dependent viscosity. We also find that the plume material could have lubricated the lithosphere-asthenosphere boundary region beneath the Indian plate. This could be a potential reason for acceleration of the Indian plate since 65 Ma.

Supplemental Material: Could the Réunion plume have thinned the Indian craton?

Supplemental Figures S1–S5 and Videos S1–S4.<br>

Supplemental Material: Could the Réunion plume have thinned the Indian craton?

Supplemental Figures S1–S5 and Videos S1–S4.<br>

Interaction of the Indian craton with the Reunion plume

&lt;p&gt;One of the fundamental characteristics of cratons is the presence of thick lithosphere of more than 200 km, whereas any standard non-cratonic lithosphere thickness is about 100 km thick. The thickness of Indian craton has remained quite controversial. Under the Indian plate, most seismic studies fail to recognise a thick lithosphere; however, a few studies using other geophysical methods (e.g., magnetotellurics) argue for a thick Indian craton. In the last 30 years, more than ten research articles estimated the thickness of the Indian craton that varied from less than 100 km to 260 km. Such controversy arose primarily because of the Reunion plume and Indian craton interaction at ~65 Ma. Some studies suggested that due to the Reunion plume's eruption underneath the Indian craton, the thick lithosphere of the Indian craton was thinned down. This thin lithosphere is attributed as one of the primary reasons for the acceleration of the Indian plate since 65 Ma. On the other hand, several studies advocated that the Reunion plume did not affect the thickness of the Indian craton. Still now, no study has actually investigated the nature of plume-craton interaction under the Indian plate and how the craton was deformed in the presence of a plume. In this study, we develop time-dependent global mantle convection models using CitcomS to understand the evolution of Indian craton for the last 100 Ma. The models are initiated at 100 Ma and are driven forward&amp;#160; up to the present day using reconstructed plate velocities at every 1 Myr interval. Our results show that it is possible to thin down the thicker cratonic lithosphere due to the eruption of the Reunion plume. We also observe that the plume could get bifurcated due to the craton, and eruptions could occur on both the eastern and western parts of the Indian continental lithosphere.&lt;/p&gt;

Linking collision, slab break-off and subduction polarity reversal in the evolution of the Central Indian Tectonic Zone

The Central Indian Tectonic Zone demarcates the zone of amalgamation between the North Indian Craton and the South Indian Craton. Presently, the major controversies in the existing tectonic models of the Central Indian Tectonic Zone revolve around the direction of subduction and the precise timing of accretion between the North Indian Craton and the South Indian Craton. A new model for the tectonic evolution of the Central Indian Tectonic Zone is postulated in this contribution, based on recent geological and geophysical evidence, combined with previously documented tectonic configurations. The present study employs the slab break-off hypothesis and subsequent polarity reversal to explain the tectonic processes involved in the evolution of the Central Indian Tectonic Zone. We propose that the subduction initiated (c. 2.5 Ga) in a S-directed system producing island-arc sequences on the South Indian Craton. The southward subduction regime culminated with slab break-off underneath the South Indian Craton between c. 1.65 Ga and 1.55 Ga, which subsequently induced subduction polarity reversal and set the course for N-directed subduction (<1.55 Ga). The final closure along the Central Indian Tectonic Zone is governed by the collisional regime during the Sausar Orogeny (1.0–0.9 Ga).