Rift induced delamination of mantle lithosphere and crustal uplift: a new mechanism for explaining Rwenzori Mountains’ extreme elevation?

摘要: With heights of 4–5 km, the topography Rwenzori Mountains, a large horst old crustal rocks located inside young passive rift system, poses question “Why are Mountains so high?”. The Cenozoic Western Rift branch East African System is situated within Late Proterozoic mobile belts between Archean Tanzania Craton and Congo Craton. special geological setting massif at node encircled by ends northern segments Lake Albert Edward suggests that mechanism responsible for high elevation Rwenzoris related to rifting process. Our hypothesis based on propagation tips, surrounding stiff lithosphere region, thereby triggering delamination cold dense mantle (ML) root reducing viscosity strength undermost lower crust. As result, this unloading induces fast isostatic pop-up less block. We term RID—“rift induced Mantle Lithosphere”. physical consistency RID tested numerically. Viscous flow 2D models approximated Finite Difference Method with markers in an Eulerian formulation. equations conservation mass, momentum energy solved multi-component system. Based laboratory data appropriate rock samples, temperature-, pressure- stress-dependent rheology assumed. Assuming simple starting model locally heated ML, ML block weakened zones becomes unstable sinks into asthenosphere, while overlying continental crust rises up. Thus, seems be viable explain geodynamically extreme uplift. Important conditions thermal anomaly ductile visco-plastic allowing significant reduction lateral density variations. situation two-sided or offset decouple laterally from most decisive. Further support may come additional thickness extensive stress field. Some parameters, such as excess temperature yield stress, very sensitive, small changes determine whether takes place not.