Influence of sedimentation, local and regional hydrothermal circulation, and thermal rebound on measurements of seafloor heat flux

摘要

We quantify the influence of environmental processes on measurements of seafloor heat flux with a new one-dimensional thermal model that includes time-varying sedimentation and boundary conditions, represents several scales of hydrothermal and transient conductive processes within basement, and allows fluid seepage through accumulating sediments. Variations in basement thermal conductivity, the extent of hydrothermal mixing in upper basement, and fluid seepage through sediments each influence seafloor heat flux by ≤2–8%. Conductive thermal rebound following the cessation of advective heat loss from the crust may lower seafloor heat flux values by ≥5–10%, even after several to several tens of million years. The new models indicate that thermal rebound takes much longer than suggested by earlier (analytical) calculations, mainly because earlier models did not account for the heat capacitance of the conductive lithosphere. Application of the new model to 3.5–3.6 Ma seafloor on the eastern flank of the Juan de Fuca Ridge suggests that anomalously low heat flux in this area is best explained by incomplete conductive thermal rebound in the last 100–200 ka, following the burial of numerous basement outcrops. Application of the new model to the eastern flank of the East Pacific Rise and extrapolation out to the age of some of the oldest remaining seafloor indicate that sedimentation corrections may be important even where accumulation rates are typical of global values. Model results also suggest that conductive thermal rebound through thick sediments may bias measurements made on moderate to old seafloor, even where there is little evidence at present for ridge-flank hydrothermal circulation.