Mantle heat budget

O Reilly SY, Griffin WL (2000) Apatite in the mantle implications for metasomatic processes and high heat production in Phanerozoic mantle. Lithos 53 217-232 Oxburgh ER, O Nions RK (1987) Helium loss, tectonics, and the terrestrial heat budget. Science 237 1583-1588... 

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). 

Note that these closed-system considerations do not require assumptions regarding the size of the reservoir. While models have assumed that it constimtes the entire mantle below 670 km (e.g., Allegre et ai, 1986), it can involve a portion of a stratified mantle or material that is distributed as heterogeneities within another mantle reservoir. However, a large deep-mantle reservoir is compatible with the K-" °Ar budget and heat- He balance. 

The core has also been considered as a source of noble gases. During formation of the Earth, the core may have incorporated sufficient quantities of solar helium to now supply ocean islands with high He/" He ratios (Porcelli and HaUiday, 2001). In this case, such ratios trace the interaction between the core and mantle (see Chapter 2.06). However, the core cannot be used to explain the radiogenic isotope budgets (see Section 4.11.3) nor the heat- He budget, and so must be coupled with a mantle model for these features. 

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