  The Earth appears non-chondritic in its abundances of refractory lithophile
elements, posing a significant problem for our understanding of its formation
and evolution. It has been suggested that this non-chondritic composition may
be explained by collisional erosion of differentiated planetesimals of
originally chondritic composition. In this work, we present N-body simulations
of terrestrial planet formation that track the growth of planetary embryos from
planetesimals. We simulate evolution through the runaway and oligarchic growth
phases under the Grand Tack model and in the absence of giant planets. These
simulations include a state-of-the-art collision model which allows multiple
collision outcomes, such as accretion, erosion, and bouncing events, that
enables tracking of the evolving core mass fraction of accreting planetesimals.
We show that the embryos grown during this intermediate stage of planet
formation exhibit a range of core mass fractions, and that with significant
dynamical excitation, enough mantle can be stripped from growing embryos to
account for the Earth's non-chondritic Fe/Mg ratio. We also find that there is
a large diversity in the composition of remnant planetesimals, with both
iron-rich and silicate-rich fragments produced via collisions.
