4:10 PM, 55 Roessler
Tea and cookies at 3:45 on the veranda

Geoneutrinos and heat production in the Earth: constraints and implications

      -- by Bill McDonough, University of Maryland

The distribution of heat producing elements in the Earth drives convection and plate tectonics. Recent results from geoneutrino studies are coincident with geochemical models of Th and U in the Earth and are increasing in quality. These detectors continue to count and thus uncertainties continue to reduced with time (at present 2 detectors are accumulating data). 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. The Mantle Urey (Ur) ratio is a measure of the radiogenic heat contribution to the total mantle heat flux and is estimated to be ~0.3 from chemical and isotopic data. Such a low mantle Urey ratio is at odds with most parameterized convection models (i.e., Ur = 0.7) for the Earth. Results from the KamLAND geoneutrino experiment challenges these geophysical models and a significant contribution from secular cooling of the mantle.