The Earth formed ~ 4.5 billion years ago, from accreting particles of dust and primitive meteorites. It is the only habitable planet in our solar system and has a unique history of extended accretion and core formation coupled with active plate tectonics. Accretion and core formation would have defined the initial elemental composition of the Earth’s interior whereas plate tectonic processes controlled chemical exchange between the Earth’s surface and interior and the distribution of elements between major geochemical reservoirs. The overarching goal of this proposal is to define the roles of these processes in the chemical evolution of the Earth and hence in the creation of a habitable planet.In order to achieve this goal I propose to investigate the partitioning of new stable isotope systems such as Ge and Se in high-pressure experiments that simulate core formation. This novel, multidisciplinary approach will provide some of the first direct constraints on the extent to which these volatile elements were partitioned into the core. We will use this information to address the fundamental issue of whether the Earth acquired its volatile elements inventory early, during core formation, or subsequently, as part of a “late veneer”. The second major theme of the proposed research uses Fe, Zn, Mo and Se stable isotopes to trace the cycling of Fe and S during subduction, the tectonic process where one plate sinks beneath another and is recycled into the Earth’s deep interior. The goal of this project is to understand the impact of subduction on the chemical and redox evolution of the Earth’s interior and the relationship between tectonic recycling and the rise of oxygen in the Earth’s atmosphere ~ 2.5 billion years ago. This theme will focus on samples of relict subducted plate material and of the Earth’s interior, obtained as fragments sampled by lavas or as ancient minerals trapped within diamonds.