The Earth's Building Blocks

International audience9 In this paper we propose an updated bulk chemical composition of the Earth based 10 on new estimates for the composition of the Earth's core. We present the different 11 cosmochemical constraints that allow us to search for the Earth's building blocks. 12 Chemical equilibrium calculations of gas – solid equilibria in solar composition gas 13 show that at first approximation the Earth is chondritic for the refractory lithophile 14 (rock-loving) elements. Elemental and isotopic compositions are then used to 15 discuss the different possible types of meteoritic material (exemplified by the 16 meteorites in our collections) that may represent the bulk Earth composition. 17 18 Introduction 1