Analysis and Mapping of an Updated Terrestrial Heat Flow Data Set

Abstract

The number of heat flow measurements at the Earth surface has significantly increased since the last global analysis (Pollack et al., 1993, https://doi.org/10.1029/93RG01249), and the most recent of them provide insights into key locations. This paper presents a new compilation, which includes approximately 70,000 measurements. Continental heat flow (67 mWm−2) does not change significantly, but the differences are more important for oceanic heat flow. The divergence with conductive cooling models is reduced significantly for young ages of the seafloor, since the most recent measurements (92 mWm−2) are significantly higher on average than the older ones (79 mWm−2). This is related to a better quality and a better sampling of measurements in regions affected by hydrothermal circulation. The total Earth heat loss derived from these most recent measurements is estimated to ∼40–42 TW and represents only 3–5 TW less than with a conductive cooling model (∼45–47 TW). Hydrothermal heat loss in the oceanic domain is estimated with a new method based on the ruggedness of the seafloor and represents ∼1.5 TW more than previous estimates. The heat flow variability on continents is so large that defining a trend with stratigraphic or tectono‐thermal age is difficult and makes extrapolation from age a poor predictor. On the other hand, additional geological and geophysical information can be combined with age for better predictions. A generalized similarity method was used here to predict heat flow on a global 0.5° × 0.5° grid. The agreement with local measurements is generally good and increases with the number and quality of proxies.

Geothermal heat flow in Antarctica: current and future directions

“…The estimated average heat flow of continental crust is 67.1 mW m -2 , whilst for oceanic crust it is 78.8 mW m -2 (Lucazeau, 2019; although estimates vary according to sampling strategy and the number of observations). The difference between continental and oceanic heat flow reflects the lower thickness of oceanic crust, with hot mantle rocks at comparatively shallow depths.…”

“…This results from the geological complexity of composite continental crust compared with oceanic crust. GHF is generally lower in stable crust away from convergent and divergent continental margins and rift basins, and higher in these magmatically active provinces (Lucazeau, 2019;Pollack et al, 1993). On a broad regional scale, continental GHF correlates negatively with age, allowing first order empirical estimation of Antarctic GHF based on its range of crustal ages ( Fig.…”

Heat flow density estimates in the Upper Rhine Graben using laboratory measurements of thermal conductivity on sedimentary rocks

“…To date, no heat flow density has been calculated for the Rittershoffen geothermal site. However, a heat flow density of 121 mW/m 2 has been calculated for a nearby borehole (SAN 1 (SANDMUHLE 1) borehole, about 3.5 km from the GRT-1 well) (Lucazeau 2019). The drilled GRT-1 and GRT-2 boreholes extend to a depth of 2580 and 3196 m MD, respectively, and target the geothermal reservoir located at the sediment-basement interface.…”

Heat flow estimates offshore Haiti in the Caribbean plate

“…The method is based on the evaluation, at each location of a grid (here, 0.1° × 0.1°), of the number of similarities with several heat‐flow proxies (called observables) at all other locations of the global grid where surface heat‐flow is known. Observables used in Figure b are from global geological and geophysical observations and models, as in the studies of Goutorbe et al () and Lucazeau (). To these global databases, we added information on the local geology of the Caribbean region (Figure a).…”

“…Bathymetric map of the Caribbean area with previous heat‐flow measurements (coloured dots) from the NGHF database (Lucazeau, ) and new measurements (coloured stars) in the Haiti offshore. The main faults are shown.…”