Interplay of variable thermal conductivity and expansivity on the thermal structure of oceanic lithosphere

The sensitivity of pressure- and temperature-dependent thermal conductivity (k: W/m/K) and the thermal expansivity (α:1/K) on the thermal structure of the oceanic plate is investigated parametrically by comparing the ocean floor depth and heat flux calculated by one-dimensional conduction model with those of GDH1, a theoretical thermal model of the oceanic lithosphere. We find that an optimum fit is obtained, when the value of thermal expansivity is ∼ 3 x 10^-5, while those associated with the thermal conductivity have many possibilities. The estimates, which give an equally good fit to the GDH1 model, of the plate thickness D (km) and the temperature at the base of the plate T_m (°C) may be given by T_m ∼ 1450 - (k_o-4.5)x100-(α-3.0 x 10^-5) x 10⁵x100, D ∼ 90 + (k_o - 4.5) x 20 - (α - 3.0 x 10^-5) x 10⁵ x 20 where k_o (W/m/K) is the lattice thermal conductivity at the ocean floor. A similar relation is obtained for constant thermal conductivity.