Several charts showing the results of hydrothermal flow modelling along a 26 km-long line located on 7-million-year-old Atlantic oceanic crust.
Results of hydrothermal flow modelling along a 26 km-long line located on 7-million-year-old Atlantic oceanic crust. Colors in (a) indicate modeled fluid flux imposing spatially variable rock porosity and permeability derived from compressional-wave velocity obtained by seismic waveform tomography. White lines display computed flow streamlines, whereas black arrows indicate predicted locations of hydrothermal plumes and convection cells. Opaque black dashed rectangle outlines zoom-in shown in (d) on the left. Colors in (b) correspond to the modeled temperature distribution imposing the same conditions and rock properties as in (a). Opaque black dashed rectangle outlines zoom-in shown in (d) on the right. The line in panel (c) indicates the percentage of total heat that is advected (transported by the fluid) in the different segments of the line. The blue line indicates segments where most heat is advected, so cooling is dominated by hydrothermal flux, whereas red lines correspond to those where heat flux is mainly driven by thermal convection. Credit: Kardell et al. [2021], Figure 7
Source: Journal of Geophysical Research: Solid Earth

Internal Earth cooling occurs by a combination of passive heat conduction and active fluid flux between the crust and the surface. While thermal conduction is the main cooling mechanism in most parts of the ocean basins, hydrothermal circulation dominates near mid-ocean ridges. However, the reach and intensity of off-axis circulation as the newly formed crust cools and migrates away from the spreading center is still poorly known.

By combining realistic maps of rock physical properties retrieved by seismic waveform tomography with hydrothermal modelling techniques, Kardell et al. [2021] present compelling evidence that hydrothermal circulation is a significant cooling factor up to crustal ages of 60 to 65 million year, in excellent agreement with previous estimates and observations. These results should be incorporated in Earth cooling models and may serve as a reference to plan future seafloor drilling expeditions.

Citation: Kardell, D. A., Zhao, Z., Ramos, E. J., Estep, J., Christeson, G. L., Reece, R. S., & Hesse, M. A. [2021]. Hydrothermal models constrained by fine-scale seismic velocities confirm hydrothermal cooling of 7–63 Ma South Atlantic crust. Journal of Geophysical Research: Solid Earth, 126, e2020JB021612. https://doi.org/10.1029/2020JB021612

—Valentí Sallarès, Associate Editor, JGR: Solid Earth

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