4D burial-exhumation patterns in a continental corner collision: insights from coupled 3D numerical modelling

With the advent of increasing computational resources, 3D geodynamic models have become more complex, for example by coupling with various types of surface process models. This allows us to model highly 3D tectonic settings more accurately, such as continental corner collisions. Such settings are sensitive to surface-tectonics interactions. However complex numerical models may be, they are only useful if we can compare them to observations. Burial-exhumation cycle or PT-t (pressure, temperature, time) analysis is one of the few ways of comparing model evolution to nature. It is common in 2D studies, but has barely been used  in 3D modelling studies (Fischer et al., 2021). Here we showcase our newly developed post-processing analysis that accurately tracks markers’ position and properties and the surface above it either forward or backward in time. We apply this method to high-resolution 3D models of the eastern corner of the India-Asia collision, conducted with I3VIS-FDSPM(Gerya & Yuen, 2007; Munch et al., 2022). In these models a strongly curved structure with high exhumation (a syntaxis) develops similar to the Eastern Himalya Syntaxis (Burg et al., 1998). We vary controlling parameters such as surface process intensity to measure their effects on exhumation and metamorphic evolution. Our novel analysis reveals that exhumation can take place perpendicular to the direction of convergence (termed lateral exhumation) under certain conditions and that rocks can undergo multiple cycles of burial-exhumation under continued convergence. We also quantify the partitioning between surface-driven and tectonically driven exhumation.  Burg, J.-P., Nievergelt, P., Oberli, F., Seward, D., Davy, P., Maurin, J.-C., Diao, Z., & Meier, M. (1998). The Namche Barwa syntaxis: Evidence for exhumation related to compressional crustal folding. Journal of Asian Earth Sciences, 16(2), 239–252. https://doi.org/10.1016/S0743-9547(98)00002-6Fischer, R., Rüpke, L., & Gerya, T. (2021). Cyclic tectono-magmatic evolution of TTG source regions in plume-lid tectonics. Gondwana Research, 99, 93–109. https://doi.org/10.1016/j.gr.2021.06.019Gerya, T. V., & Yuen, D. A. (2007). Robust characteristics method for modelling multiphase visco-elasto-plastic thermo-mechanical problems. Physics of the Earth and Planetary Interiors, 163(1), 83–105. https://doi.org/10.1016/j.pepi.2007.04.015Munch, J., Ueda, K., Schnydrig, S., May, D. A., & Gerya, T. V. (2022). Contrasting influence of sediments vs surface processes on retreating subduction zones dynamics. Tectonophysics, 836, 229410. https://doi.org/10.1016/j.tecto.2022.2294