The distribution of radioactive heat production in I‐ and S‐type granites and residual source regions: Implications to high heat flow areas in the Lachlan Fold Belt, Australia

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Abstract
An analysis of the uranium and thorium fractionation processes in various granites implies a direct dependence on processes of magmatic differentiation, the magma source materials, and residual accessory phases; suggesting that no universal, vertical heat‐producing element distribution may be applied to all granite crust. Metaluminous I‐type granites show evidence for downward decreases in heat‐producing elements within the plutons. The heat‐producing element content of I‐type residual source regions is probably similar to that of the most mafic I‐type granites. The fractionation trends of peraluminous S‐type granite indicate that no significant change in heat‐producing elements should occur with depth in the plutons. Geochemical evidence indicates that residual source regions of S‐type granites will contain high concentrations of heat‐producing elements and reside deep in the crust. Anomalously high heat flow in southeastern Australia corresponds to areas of S‐type granites and may be largely due to deep crustal radioactivity, rather than Cainozoic mafic magmatism.