Relative Contributions of Uranium, Thorium, and Potassium to Heat Production in the Earth

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Science  31 Jan 1964:
Vol. 143, Issue 3605, pp. 465-467
DOI: 10.1126/science.143.3605.465


Data from a wide variety of igneous rock types show that the ratio of potassium to uranium is approximately 1 X 104. This suggests that the value of K/U ≈1 X 104 is characteristic of terrestrial materials and is distinct from the value of 8 X 104 found in chondrites. In a model earth with K/U ≈ 104, uranium and thorium are the dominant sources of radioactive heat at the present time. This will permit the average terrestrial concentrations of uranium and thorium to be 2 to 4.7 times higher than that observed in chondrites. The resulting models of the terrestrial heat production will be considerably different from those for chondritic heat production because of the longer half-life of U238 and Th238 compared with K40