Understanding the stability of cratons within tectonically active plates stands as one of the grand challenges in geodynamics. Through the development of numerical models of craton evolution, my research aims to shed light on why certain cratons have remained stable for over 3 billion years, while others, such as the North China Craton, have undergone complete destruction.
My findings suggest that the combined effects of viscosity and thickness play a crucial role in enhancing the strength of cratons, thereby shielding them from tectonic recycling. Two key theoretical insights:
1. Stress and strain-rates exhibit an inverse relationship at the base of the lithosphere , leading to decreased deformation beneath thick cratons.
2. The thickness and viscosity of cratons induce a convective self-compression , further enhancing their resistance against disintegrating forces.
My research also indicates that cratons require a minimum viscosity of 10²³ Pa.s and that the surrounding asthenosphere should not have a viscosity lower than 10²⁰ Pa.s to support their long-term stability.
However, cratons face potential thinning or complete destruction under certain circumstances. Thermal weakening induced by mantle plumes, as observed in the Indian craton, or metasomatic weakening caused by mantle/slab fluids, as seen in the case of the North China Craton, can lead to their demise. My study delves into these mechanisms of craton destruction and compares the timescales involved in the process.
Publications
>> [7] J.Paul*, A. Spang, A. Piccolo. Flat slab induced weakening and destruction of the North China craton, (submitted)
>> [6] J. Paul*, C.P. Conrad, T.W. Becker, A. Ghosh, 2023. Convective self-compression of cratons and the stabilization of old lithosphere. Geophysical Research Letters, 50, e2022GL101842. [Open access]
>> [5]. J. Paul, A. Ghosh, 2022. Could the Reunion plume have thinned the Indian craton?, Geology
>> [4] J. Paul, A. Ghosh, 2020. Evolution of cratons through the ages: A time-dependent study, Earth and Planetary Science Letters, , 531, 115962. [Online version]
>> [2] J. Paul*, A. Ghosh, C.P. Conrad, 2019. Traction and strain-rate at the base of the lithosphere: An insight into cratonic survival. Geophysical Journal International, 217(2), 1024-1033

Numerous speculations surround the impact of grain size on mantle dynamics, yet the lack of available data, whether experimental or natural, poses a substantial challenge in precisely determining this influence. Recent mineral physics experiments have, however, provided estimates for the grain growth rate of bridgmanite-ferropericlase, the primary mineral assemblage in the lower mantle. As part of the European Research Council project UltraLVP: Chemistry and transport properties of bridgmanite controlling lower-mantle dynamics , I incorporated bridgmanite-ferropericlase grain growth data into numerical models to investigate the effect of grain size in lower mantle viscosity.
The outcomes of the study revealed no significant impact of grain size on controlling lower mantle viscosity. This result can be attributed to the slow growth of bridgmanite-ferropericlase compared to upper mantle olivine grain growth, where small grain sizes have minimal influence on lower mantle viscosity. Conversely, if forced to increase like olivine, the growth of bridgmanite-ferropericlase grains leads to a dislocation creep-induced deformation, resulting in grain size-independent viscosity.
Publications
>> J. Paul*, G. Golabek, A. Rozel, P. Tackley, T. Katsura, H. Fei. Insignificant effect of bridgmanite-ferropericlase grain size evolution on Earth’s lower mantle viscosity (Under Review).

This work is part of a project investigating the style of hydrothermal mineralisation and ore formation in and around Delhi-Aravalli fold belt. I have worked on the geochemical and geostatistical nalysis of amphibole originated from the hydrothermal processes. We detected three generations of amphiboles. The last stage of amphibole formation (A3) is probably associated with IOCG type mineralisation of this area.