Steady state geothermal model of the crust and the problem of the boundary conditions : application to a rift system, the southern Rhinegraben

Jean-Jacques Royer and Michel Danis. ( 1988 )
in: Tecnophysics, 156:3-4 (239--255)

Abstract

Seismic, gravity and magnetotelluric data are used to model the two-dimensional heat transfer beneath an E-W vertical cross section ranging from the Black Forest, Rhinegraben to the southern Vosges. The temperature field at the present time has been calculated taking into account the effect of temperature on thermal conductivity and the radiogenic heat sources. Heat flow density conditions at depth, computed by solving iteratively the heat equation and comparing the heat flow measured at the surface with the calculated one, have been used. As the resulting heat flow condition at depth is very sensitive to the interpolation method used to estimate the heat flow values at the surface, a confidence interval of the thermal field is then proposed by varying the possible mantle heat flow conditions using a Monte Carlo method. Arguments based on petrological considerations suggest that a temperature condition could be used at the Moho. The resulting model involves regional surface heat flow densities ranging from a normal crustal value of 70 mW m−2 to a highest value of 105 mW m−2, in agreement with actual measurements. The results are compatible with those obtained by the German KTB Program on the Black Forest (Gehlen et al., 1986) and on the Swiss traverse (Rybach, 1979). They suggest that the regional high heat flow (105 mW m−2) measured in the southern Vosges is caused by the high radiogenic elements content (especially thorium) of the Crêtes sub-alkaline granite and by an asymmetry in the lithospheric heating. High heat flow density values observed along the Rhinegraben give evidence of heat refraction phenomena around high conductivity rocks.

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BibTeX Reference

@ARTICLE{,
    author = { Royer, Jean-Jacques and Danis, Michel },
     title = { Steady state geothermal model of the crust and the problem of the boundary conditions : application to a rift system, the southern Rhinegraben },
     month = { "apr" },
   journal = { Tecnophysics },
    volume = { 156 },
    number = { 3-4 },
      year = { 1988 },
     pages = { 239--255 },
       doi = { 10.1016/0040-1951(88)90062-5 },
  abstract = { Seismic, gravity and magnetotelluric data are used to model the two-dimensional heat transfer beneath an E-W vertical cross section ranging from the Black Forest, Rhinegraben to the southern Vosges. The temperature field at the present time has been calculated taking into account the effect of temperature on thermal conductivity and the radiogenic heat sources. Heat flow density conditions at depth, computed by solving iteratively the heat equation and comparing the heat flow measured at the surface with the calculated one, have been used. As the resulting heat flow condition at depth is very sensitive to the interpolation method used to estimate the heat flow values at the surface, a confidence interval of the thermal field is then proposed by varying the possible mantle heat flow conditions using a Monte Carlo method. Arguments based on petrological considerations suggest that a temperature condition could be used at the Moho. The resulting model involves regional surface heat flow densities ranging from a normal crustal value of 70 mW m−2 to a highest value of 105 mW m−2, in agreement with actual measurements.

The results are compatible with those obtained by the German KTB Program on the Black Forest (Gehlen et al., 1986) and on the Swiss traverse (Rybach, 1979). They suggest that the regional high heat flow (105 mW m−2) measured in the southern Vosges is caused by the high radiogenic elements content (especially thorium) of the Crêtes sub-alkaline granite and by an asymmetry in the lithospheric heating. High heat flow density values observed along the Rhinegraben give evidence of heat refraction phenomena around high conductivity rocks. }
}