Lithospheric mantle delamination control on orogenic plateau formation

The convergence of continents is accommodated by the subduction of the oceanic lithosphere, followed by continental collision. A long-lasting collisional stage can lead to the rise of wide and high orogenic areas, such as the Tibetan or Iranian Plateau. The mechanisms maintaining high convergence rates during continental collision remain debatable. A viable process involves the peeling off and sinking of the dense continental mantle lithosphere and rise of the asthenosphere underlying crustal accretion. This geodynamic process is so called “delamination”, which is invoked in accounting for a variety of geological and geophysical phenomenon such as widespread igneous rocks, rapidly uplift in geological history, and high velocity anomaly in seismic tomography observed in many orogenic plateaus (Bird, 1979).

Different regimes of delamination would lead to different modes of mantle convection and crustal deformation, resulting in various surface expressions and the formation of orogenic plateaus. In this study, we simulate oceanic subduction, followed by continental collision and delamination. We aim to understand and quantify the spatial and temporal evolution of orogenic plateau formation and its connection to lithospheric mantle delamination, upper and lower crustal deformation and deep subduction dynamics.

We use 2D numerical modeling with the I2ELVIS code (Gerya & Yuen, 2003), simulating visco-plastic rheology, hydration and dehydration processes, melting and surface processes. Our initial setup involves two continents separated by a ca. 700 km wide oceanic domain. We present preliminary results on the influence of different subduction velocities, plate rheology and different intensity of surface processes for different geodynamic regimes of orogeny and orogenic plateau formation.

Reference

Bird, P. (1979). Continental delamination and the Colorado Plateau. Journal of Geophysical Research: Solid Earth, 84(B13), 7561-7571.

Gerya, T. V., & Yuen, D. A. (2003). Characteristics-based marker-in-cell method with conservative finite-differences schemes for modeling geological flows with strongly variable transport properties. Physics of the Earth and Planetary Interiors, 140(4), 293-318.