Heat flow variations over Hawaiian swell controlled by near-surface processes, not plume properties

Abstract

The commonly accepted explanation for the Hawaiian-Emperor chain of sea-mounts is that it is caused by drift of the Pacific plate over a relatively stationary plume of hot material upwelling from deep within the Earth. As the classic example of this phenomenon, geophysical data from the Hawaiian chain, particularly heat flow data, have been used to infer the physical properties of mantle plumes, such as their temperature and how they interact with the overlying plate. However, the heat flow data have defied simple explanation and are often at odds with other geophysical observations. Here I show that variations in heat flow are highly correlated with changes in the thermal conductivity of the surface sediments rather than with any expected variability in heat flux reaching the surface from a mantle plume. This correlation of heat flow with thermal conductivity is exactly what is predicted if the upper oceanic crust acts as a permeable aquifer in a flow system that laterally redistributes heat within the uppermost oceanic crust. The spatially- averaged mean of the heat flow values is well determined and indicates that the oceanic plate near Hawaii is hotter than expected for its age, consistent with the plume hypothesis. However, the effect of the fluid circulation is to obscure any heat flow pattern that could be used to infer the structure of the plume or its interaction with the overlying lithosphere.