Radiogenic heat production of crustal rocks: An assessment based on geochemical data

Abstract

A survey of the geochemical literature and unpublished data has resulted in the classification of U, Th, and K concentrations by rock type. Over 2500 data entries have been compiled, permitting calculation of their radiogenic heat production. In the igneous rocks mean heat production ranges from highs of 12‐20 heat production units (HPU: µ Wm −3 ) in some peralkaline intrusives, through ∼ 4 HPU in acidic, ∼ 2 in intermediate, and ∼ 1 in basic rocks, to a low of 0.3 HPU in ultramafic rocks. Siliceous clastic rocks generally have greater heat production (2 to 4 HPU) than do chemical sedimentary rocks, including the carbonates (0.4 to 2 HPU). The heat production of metamorphic rocks generally depends on the radioelement contents of their igneous and sedimentary predecessors, modified by metamorphic processes. Based on estimates of the proportion of the continental crust that specific rock types occupy, the weighted mean radiogenic heat production of the upper continental crust estimated from this data base is ∼ 3 HPU.