Mantle heat production

The energy that powers terrestrial processes is derived primarily from the sun and from the Earth s internal heat production (mostly radioactive decay). Solar energy drives atmospheric motions, ocean circulation (tidal energy is minor), the hydrologic cycle, and photosynthesis. The Earth s internal heat drives convection that is largely manifested at the Earth s surface by the characteristic deformation and volcanism associated with plate tectonics, and by the hotspot volcanism associated with rising plumes of especially hot mantle material. 

Rudnick R. L. and Nyblade A. A. (1999) The thickness and heat production of Archean hthosphere constraints from xenohth thermobarometry and surface heat flow. In Mantle Petrology Field Observations and High Pressure Experimentation (eds. Y. Fei, C. Bertka, and B. O. Mysen). The Geochemical Society, Houston, vol. 6, pp. 3—12. 

Russell J. K., Dipple G. M., and Kopylova M. G. (2001) Heat production and heat flow in the mantle lithosphere, Slave craton, Canada. Phys. Earth Planet. Int. 123, 27 -44. 

O Reilly S. Y. and Griffin W. L. (2000) Apatite in the mantle imphcations for metasomatic processes and high heat production in Phanerozoic mantle. Lithos 53, 217-232. 

As a possible radiogenic heat source in the Earth, the presence of an appreciable amount of potassium in the core was suggested over 30 years ago (Lewis, 1971 Hall and Murthy, 1971). The estimated concentration of potassium in the mantle is 240 ppm (McDonough and Sun, 1995). If the concentration of potassium in the core is at a comparable level, the present-day heat production due to would be on the order of 10 W, enough to drive the geodynamo. Radiogenic heat production due to also has direct implications for convection in the outer core, heat flux at the CMB, and the dynamics of the lower mantle. Recent studies of plume dynamics and considerations of the age of the inner core have inspired a renewed interest in the potassium content of the core (Murthy et ai, 2003, and references therein see Chapter 2.15). 

Alternatively, one can attempt to estimate the bulk crustal heat production directly from the heat flow data and local studies of crustal stmcture. This requires estimates of the mantle heat flow Qm, which can be obtained in several ways. 

The area weighted heat flow for all provinces older than 200 Ma is 51 mW m (Stein, 1995). Estimates of the mantle heat flow by various authors vary between 11 mW m andl8 mW m (Jaupart and Mareschal, 1999). After removing the mantle heat flow, the average contribution of the crust to the surface heat flow in stable continental regions is between 33 mW m and 40 mW m. This implies that the bulk crustal heat production is 0.9 0.1 p,W m. ... 

Heat production for the bulk continental crust in Table 7 is calculated using the crustal age distribution of model 2 in Rudnick and Fountain (1995) and is in the upper end of the range of values from global crust/mantle budgets (Table 2). 

In stable continents, the cmstal contribution is obtained by removing the mantle heat flow from the surface heat flow. The mantle heat flow is constrained by the heat flow and heat production data and by the required consistency of thermal data with lithospheric thickness from seismology and xenolith studies. Results from heat flow studies yield an average heat production of 0.77 0.08 pW m for the Precambrian cmst and 1.03 0.08 pW m for the Phanerozoic. The global value for each age group lumps together different types of cmstal structures. 

Forster A. and Forster H.-J. (2000) Crustal composition and mantle heat flow implications from surface heat flow and radiogenic heat production in the Variscan Erzgebirge (Germany). J. Geophys. Res. 105, 27917—27938. 

Rudnick R. L. and Nyblade A. A. (1999) The thickness and heat production of Archean lithosphere constraints from xenolith thermobarometry and surface heat flow. In Mantle... 

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