ANALOGUE MODELING: STRUCTURAL DEVELOPMENT ABOVE A SUBDUCTED FLAT SLAB

The Himalayan-Tibetan Orogen is a type example of continent-continent collision, yet our understanding of the mechanisms associated with plateau uplift is limited. Several models exist to explain the development of plateau uplift including thickness increase by crustal insertion (Zhou and Morgan, 1995), Diffused homogenous thickening (Dewey et al., 1988), and mantle dynamics (England and Housemann, 1988). Recent studies have demonstrated that the Tibetan Plateau crust between the Himalaya and the Qiangtang terrain is underlain by greater Indian mantle lithosphere (Johnson, 2002), which may have played a significant role in development of Cenozoic structures during overall north-south shortening. In this study, I use 3D analogue modeling to investigate strain partitioning and deformation patterns in a setting underlain by a shallow-rigid plate in a convergent setting. Experiments were conducted in a 1m x 1m x 40cm analogue modelling box using a wood plate, silicon-corundum mixture, and loose sand for a scaled layered crust. A series of exploratory experiments were conducted in which we modified convergence rate and underlying rigid plate geometry to test the effects of each. We report surface uplift, total displacement, transverse strain perpendicular and parallel to convergence, minimum normal strain, vertical axis rotation, horizontal shear, and topographic changes for each experiment. We note several relationships between surface deformation and underlying plate geometry including a broad bulge develops on the surface, above the wood base plate, with a lateral geometry that mimics the underlying wood plate geometry and distributed deformation in front of the underlying plate. Results from these experiments may help elucidate the relationship of structures in the Himalayan-Tibetan Orogen and the presence of a subducted indenter.