Origins of Earth's volatiles from experiments and modeling of accretion and core formation

Abstract

This dissertation explores the two key processes– core formation and volatile loss– that shaped the geochemical signatures of the silicate Earth during its formation. We first improve existing models of core formation by incorporating a melt-scaling law to quantify the volume of melt produced by giant impacts. Volatile elements (H, C, and N) are integrated into these core formation models to investigate their distributions between core, mantle, atmosphere, and loss to space during Earth’s formation. Significant C, and potentially N, could be lost during the giant impact stage of Earth’s formation. The last two chapters focus on moderately volatile elements, beginning with high-pressure experiments on the metal–silicate partitioning of Pb. These experiments clarify the bulk Earth abundance of Pb, which confirms the plateau in moderately volatile element abundances with 50% condensation temperatures below ~750 K. Finally, isotopic chronometers that are sensitive to the timing of volatile loss (Pd–Ag, Mn–Cr, I–Xe, and U–Pb), are coupled with core formation models. The moderately volatile element budget of Earth and its precursors was likely set within the first few million years of the Solar System.