Hot and Cold Zones of the Southeast Indian Ridge and Their Impact on the Specific Features of Its Structure and Magmatism (Numerical and Physical Simulation)
The paper describes the specific features of alteration of the bottom topography and morphostruc-tural segmentation along the strike of the Southeast Indian Ridge (SEIR) and in the impact zones of the Am-sterdam-St. Paul hot spot and the anomalous zone of the relatively cold mantle in the area of the Australian-Antarctic discordance. The change in the thermal regime and strength of the crust in the axial and off-axial zones of the SEIR Indian Ridge has been numerically estimates. A correlation between the thermal-rheological condition of the axial zone of the ridge with the seabed topography and the morphostructural segmentation and magmatism features has been established. The numerical simulation results make it possible to assume the presence of along-axis counterflows of the asthenosphere under the axial zone of the SEIR. One of them, which was initiated by the Amsterdam-St. Paul point and the Kerguelen plume, is oriented from west to east, while and the second, located east of the Australian-Antarctic discordance, is oriented from east to west. Taking into account the numerical simulation results of the thermal regime and the change in thickness of the brittle layer in the axial lithosphere, we performed a physical simulation of the impact of temperature anomalies in the mantle on the specific features of crust deformation in the axial zones of the ridge. The experimental simulation showed that the presence of a thermal anomaly in the sublithosphere mantle in the form of a local heat source (hot spot) will noticeably influence the geometry of the rift axis and its position in relation to the hot spot. An area of anomalous topography forms under the action of the hot spot, traces of which are preserved in the off-axis spreading flank zones, as in the case of the Amsterdam-St. Paul hot spot. A more contrasting and dissected topography forms in zones with a relatively low typical mantle temperature in the process of crust accretion.