Crust heat flow

The Roman Province is characterised by less than 25 km thick crust (Pi-romallo and Morelli 2003) and by anomalous heat flow of more than 100 mWm"2 at a regional scale (Mongelli and Zito 1991 Mongelli et al. 1991),... 

Rehnements of the Taylor and McLennan (1985) model are provided by McLennan and Taylor (1996) and McLennan (2001b). The latter is a modihcation of several trace-element abundances in the upper crust and as such, should not affect their compositional model for the bulk crust, which does not rely on their upper crustal composition. Nevertheless, McLennan (2001b) does provide modihed bulk-crust estimates for niobium, rubidium, caesium, and tantalum (and these are dealt with in the footnotes of Table 9). McLennan and Taylor (1996) revisited the heat-flow constraints on the proportions of mahc and felsic rocks in the Archean crust and revised the proportion of Archean-aged crust to propose a more evolved bulk crust composition. This revised composition is derived from a mixture of 60% Archean cmst (which is a 50 50 mixture of mahc and felsic end-member lithologies), and 40% average-andesite cmst of Taylor (1977). McLennan and Taylor (1996) focused on potassium, thorium, and uranium, and did not provide amended values for other elements, although other incompatible elements will be higher (e.g., rubidium, barium, LREEs) and compatible elements lower in a cmst composition so revised. 

McLennan S. M. and Taylor S. R. (1996) Heat flow and the chemical composition of continental crust. J. Geol. 104 396-377. 

Sclater J. G., Jaupart C. J., and Galson D. (1980) The heat flow through oceanic and continental crust and the heat loss of the earth. Rev. Geophys. Space Phys. 18, 269—311. 

Crustal component of heat flow for a 41 km thick crust. 

Shaw et al., 1986 Gupta et al, 1991 Jaupart et al., 1998 Gao et al., 1998). The value of Shaw et al. (1986) for the Canadian Shield is not consistent with the heat flow data. Thus, one may not apply one estimate for one province to another province. A further difficulty is that the crustal thickness varies significantly. For example, the crust of the North China craton is thinner than average (—35 km Gao et al., 1998). 

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. ... 

Table 7 Estimates of bulk continental crust heat production from heat flow data.

Jaupart C., Sclater J. G., and Simmons G. (1981) Heat flow smdies constraints on the distribution of uranium, thorium and potassium in the continental crust. Earth Planet. Sci. Lett. 52, 328-344. 

---