Uncertainties in the composition of Earth, its core and silicate sphere

Abstract

A self consistent model for the Earth has the heat producing elements, K, Th and U concentrated in the silicate Earth, with negligible quantities stored in the core. With uncertainties reported at the 2 sigma level, the silicate Earth has 80 ± 25 ng/g Th and 20 ± 8 ng/g U, with a Th/U of 3.9 ± 0.4; it also has a K/U of 1.38 ± 0.26 * 10 4 and a K content of 280 ± 120 μg/g. Thus, the radiogenic contribution to the Earth's thermal power is 21 ± 4 TW relative to a total output of 46 ± 6 TW. 1. Introduction As geoneutrino data are accumulated, the particle physics community looks to the geological community for insight and guidance into the composition of the bulk Earth and its major reservoirs: the crust, mantle and core. A fundamental question is -how well do we know the composition of the Earth, including its core and mantle, as these regions not directly accessible? Establishing uncertainties on geochemical estimates depends critically on what are the known knowns, known unknowns, and worse yet, the unknown unknowns, to quote Don Rumsfeld. This paper examines the absolute uncertainties in our Earth models and provides a reference frame for future geoneutrino tests.