Strain localization at the margins of strong lithospheric domains: insights from analogue models

The lateral variation of the mechanical properties of continental lithosphere is an important factor controlling the localization of deformation and thus the deformation history and geometry of intra-plate mountain belts. A series of three-layer lithospheric-scale analog models, with a strong domain (SD) embedded at various depths, are presented to investigate the development of topography and deformation patterns by having laterally heterogeneities within a weak continental lithosphere. The experiments, performed at a constant velocity and under normal gravity, indicate that the presence or absence of the SD controls whether deformation is localized or distributed at a lithospheric-scale. Deformation and topography localizes above the edges of the SD while the SD region itself is characterized by minor amounts of surficial deformation and topography. The depth of the SD (within the ductile crust, ductile mantle lithosphere, or both) controls the pattern of deformation and thus the topography. The presence of a SD in the ductile crust or in the mantle results in limited surficial topographic effects but large variations in the Moho topography. Strong Moho deflection occurs when the SD is in the ductile crust while the Moho remains almost flat when the SD is in the mantle. When the SD occupies the ductile lithosphere, the SD is tilted. These analog experiments provide insights into intra-plate strain localization and could in particular explain the topography around the Tarim Basin, a lithospheric-scale heterogeneity north of the India-Asia collision zone.