Parameterized Mantle Convection Analysis for Crustal Processes
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Thermal convection is considered as the main heat transport mechanism in the mantle that brings heat from earth’s interior to the base of the lithosphere. Many large-scale geological and tectonic processes such as initiation of plate tectonics and its persistence throughout the geological history, formation and stability of cratons, generation of komatiites in Archaean, etc. are controlled by heat. These processes and the presence of radioactive elements support the view that the early earth would have been at a much higher temperature compared to the present state indicating that the mantle convection would have been more vigorous during the early Archaean. Therefore, reconstruction of evolution of average mantle temperature and the geotherm of the convecting mantle through the geological history is important for the understanding of the geological processes. This chapter deals with simplified treatment of mantle convection, so called parameterized model of thermal convection. From the energy balance for the mantle, an equation for the average temperature is derived using Nusselt and Rayleigh number relationship and temperature dependent viscosity. Solution of this nonlinear equation, given evolution of core heat flux and decay of radioactive elements, yields the cooling history of average mantle temperature. Implications of the mantle cooling history on the generation of komatiites, initiation of plate tectonics and craton stability are discussed.
KeywordsHeat Flux Rayleigh Number Thermal Convection Mantle Convection Bottom Boundary Layer
RNS is grateful to INSA, India for the award of a Senior Scientists scheme to him. Contribution under PSC0204 (INDEX) and MLP6107-28(AM).
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