Reassessing the Thermal Evolution of Oceanic Lithosphere Using Updated Basement Depth and Heat Flow Measurements

Half-space cooling and plate models of varying complexity have been proposed to account for variations in basement depth and heat flow as a function of age in the oceanic realm. Here, we revisit this well-known problem using our latest database of 2030 measurements of depth to oceanic basement, corrected for sedimentary loading and variable crustal thickness, and 3766 heat flow measurements. Joint inverse modeling of both databases demonstrates that the half-space cooling model yields a mid-oceanic axial temperature that is > 300 °C cooler than permitted by petrologic constraints and does not produce the flattening observed in both datasets at old ages. We next investigate a suite of increasingly sophisticated plate models and conclude that the optimal model requires incorporation of experimentally determined temperature- and pressure-dependent conductivity, expansivity and specific heat capacity, as well as a low conductivity crustal layer. This revised model has a mantle potential temperature of 1302 ± 60 °C which honors independent geochemical constraints, an initial ridge depth of 2.6 ± 0.3 km, and a plate thickness of 135 ± 30 km. It predicts that the maximum depth of intraplate earthquakes is bounded by the 700 °C isothermal contour, consistent with laboratory creep experiments on olivine aggregates. Estimates of the lithosphere-asthenosphere boundary derived from azimuthal anisotropy studies coincide with the 1175 ± 50 °C isotherm. The gravity contribution of this plate model is consistent with observations in the Atlantic, Indian and Pacific Oceans and can be subtracted from the observed field to isolate gravity anomalies generated by sub-plate convective processes and lithospheric heterogeneity.