The first 150 M.yrs of Earth evolution were the most dramatic in the history of the planet, setting the scene for the development of plate tectonics, the Earth’s magnetic field and the origin of life. By the end of this period Earth had separated into core, mantle, crust and atmosphere and the Moon had formed by, it is presumed, a giant impact near the end of accretion. The aim of this project is to quantify the processes by which, during Earth’s earliest evolution, the chemical elements were distributed into different geological reservoirs, to determine the timings and conditions under which this partitioning occurred and to determine how Earth’s interior reached its current composition and oxidation state. The principal method involves experiments at high temperatures (1400-3000K) and high pressures (0-25 GPa, equivalent to 0-700 km depth) in which the silicate materials of Earth’s mantle, crust and core are equilibrated with one another and with a gas phase under controlled conditions. Elements which constrain the major processes of growth and differentiation of the Earth are added to each experiment in trace concentrations similar to those found on Earth. After the experiment the products (typically 2-60 mgm) are sectioned and their chemical compositions determined by microanalysis. By varying the experimental conditions the dependence of the geochemical behaviour of the different elements on physical conditions such as pressure, temperature and oxidation state will be determined. These measurements of chemical fractionations between different phases are complemented by experimentally-measured isotopic fractionations between the same phases. These will enable us to interpret the observed isotopic differences between Earth and primitive planetary material (as represented by chondritic meteorites) in terms of the processes which formed our planet.
Fields of science
Call for proposal
See other projects for this call