Research Collaborations

Craton Dynamics

Understanding the stability of cratons on a tectonically active planet like Earth remains one of the grand challenges in geodynamics. Through the development of numerical models of craton evolution, our research aims to shed light on why some cratons have remained stable for over 3 billion years, while others, like the North China Craton, have undergone complete destruction.


Paul and Ghosh, 2020, EPSL.

Key Findings

Our findings suggest that the combination of viscosity and thickness plays a crucial role in enhancing cratonic strength, shielding them from tectonic recycling. Two key theoretical insights emerge:

  1. Stress and strain rates exhibit an inverse relationship at the lithosphere's base, reducing deformation beneath thick cratons.
  2. Cratonic thickness and viscosity induce convective self-compression, further reinforcing their resistance to disintegration.

Our research also indicates that cratons require a minimum viscosity of 10²³ Pa·s and that the surrounding asthenosphere must have a viscosity no lower than 10²⁰ Pa·s to sustain long-term stability.

Mechanisms of Destruction

Paul et al., 2025, Tectonophysics.

However, cratons can undergo thinning or destruction under certain conditions. Thermal weakening by mantle plumes (e.g., the Indian Craton) or hydration weakening from mantle/slab fluids (e.g., the North China Craton) can lead to their demise. My work explores these destruction mechanisms and compares their associated timescales.


Publications
>> 8. J. Paul, A. Spang, A. Piccolo (2025). Hydration weakening and destruction of the North China Craton, Tectonophysics, 908, 230756, https://doi.org/10.1016/j.tecto.2025.230756.
>> [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

Grain size dependent Rheology



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. J. Golabek, A. B. Rozel, P. J. Tackley, T. Katsura and H. Fei (2024). Effect of bridgmanite-ferropericlase grain size evolution on Earth's average mantle viscosity: Implications for mantle convection in early and present-day Earth. Progress in Earth and Planetary Sciences, 11 (64) [https://doi.org/10.1186/s40645-024-00658-3] .