Hotspot swells revisited

Abstract

The first attempts to quantify the width and height of hotspot swells were made more than 30 years ago. Since that time, global bathymetry, ocean-floor age, and sediment thickness datasets have improved considerably. Swell heights and widths have been used to estimate the heat flow from the core-mantle boundary, constrain numerical models of plumes, and as an indicator of the origin of hotspots. In this paper, we repeat the analysis of swell geometry and buoyancy flux for 54 hotspots, including the 37 considered by Sleep (1990) and the 49 considered by Courtillot et al. (2003), using the latest and most accurate data. We are able to calculate swell geometry for a number of hotspots that Sleep was only able to estimate by comparison with other swells. We find that in spite of the increased resolution in global bathymetry models there is significant uncertainty in our calculation of buoyancy fluxes due to differences in our measurement of the swells' width and height, the integration method (volume integration or cross-sectional area), and the variations of the plate velocities between HS2-Nuvel1a (Gripp and Gordon, 1990) and HS3-Nuvel1a (Gripp and Gordon, 2002). We also note that the buoyancy flux for Pacific hotspots is in general larger than for Eurasian, North American, African and Antarctic hotspots. Considering that buoyancy flux is linearly related to plate velocity, we speculate that either the calculation of buoyancy flux using plate velocity over-estimates the actual vertical flow of material from the deep mantle or that convection in the Pacific hemisphere is more vigorous than the Atlantic hemisphere.

Geochemistry and Distribution of Recycled Domains in the Mantle Inferred From Nd and Pb Isotopes in Oceanic Hot Spots: Implications for Storage in the Large Low Shear Wave Velocity Provinces

“…However, we do not find a relationship between hot spot buoyancy fluxes (from King & Adam, 2014) and the minimum 143 Nd/ 144 Nd at hot spots examined here, which argues against plume buoyancy controlling the magnitude of the EM signature observed at hot spots. Due this uncertainty, we cannot exclude a model whereby EM domains are distributed ubiquitously in the lower mantle, but that plumes located outside of the LLSVPs are simply too weak (compared to plumes located inside the LLSVPs) to entrain deep EM domains.…”

“…However, he left evaluating examination of extreme high 206 Pb/ 204 Pb and low 143 Nd/ 144 Nd signatures to future work. b All hot spots and locations are after King and Adam (2014), except for the Manus Basin hot spot, which is added to the hot spot catalogue here. We evaluate whether the most extreme EM and HIMU oceanic hot spots exhibit geographic patterns as a function of latitude and longitude, and whether extreme EM and HIMU compositions are geographically associated with the LLSVPs.…”

Lithospheric Thinning by Mantle Plumes

“…Moreover, the plume mass flux is prescribed to values of between 0.5 and 7 Mg/s beneath the lithosphere, in agreement with surface observations of topographic swells (e.g. Davies, 1988;Sleep, 1990;King & Adam, 2014).…”

Probing the Earth’s Deep Interior Through Geochemistry

“…This result tended to support the idea that plumes develop from a thermal boundary layer at the base of the mantle, the temperature increase across which might be in excess of 1000 °C. King and Adam (2014) revisited the question of buoyancy fluxes and their estimates tend to be lower than those of Sleep and Davies, as is their estimated total plume heat flux. At the same time, estimates of heat flow from the core have increased (Pozzo et al, 2012) so that the most recent estimates of plume heat flux are significantly lower than the heat flux from the core.…”

“…Exploring the full geodynamic implications of this is well beyond the scope of this paper, but it does suggest that plumes play a greater role in mantle convection and everything related to it, including plate tectonics and continent evolution, than previously thought. King and Adam (2014) recently revisited the question of hot spot swells (the broad topographic anomalies associated with hot spots) and the plume flux. The total heat flux they derive, about 2 TW, is similar to that calculated by Davies (1988) and Sleep (1990), but they find that all these estimates have very considerable uncertainty.…”