Geoneutrinos and Heat Production in the Earth: Constraints and Implications

Recent results from antineutrino (geoneutrino) studies at KamLAND are coincident with geochemical models of Th and U in the Earth. KamLAND and Borexino detectors are on line, thus uncertainties in counting statistics will be reduced as data are accumulated. The SNO+ detector, situated in the middle of the North American plate will come on line in ∼3 yrs and will be best suited to yield a precise estimate of the continental contribution to the Earth's Th and U budget. The distribution of heat producing elements in the Earth drives convection and plate tectonics. Geochemical models posit that ∼40% of the heat producing elements are in the continental crust, with the remainder in the mantle. Although models of core formation allow for the incorporation of heat producing elements, the core contribution of radiogenic heating is considered to be negligible. Most parameterized convection models for the Earth require significant amounts of radiogenic heating of the Earth, a factor of two greater than geochemical models predict. The initial KamLAND results challenge these geophysical models and support geochemical models calling for a significant contribution from secular cooling of the mantle.