  We use a hybrid numerical approach to simulate the formation of the Moon from
an impact-generated disk, consisting of a fluid model for the disk inside the
Roche limit and an N-body code to describe accretion outside the Roche limit.
As the inner disk spreads due to a thermally regulated viscosity, material is
delivered across the Roche limit and accretes into moonlets that are added to
the N-body simulation. Contrary to an accretion timescale of a few months
obtained with prior pure N-body codes, here the final stage of the Moon's
growth is controlled by the slow spreading of the inner disk, resulting in a
total lunar accretion timescale of ~10^2 years. It has been proposed that the
inner disk may compositionally equilibrate with the Earth through diffusive
mixing, which offers a potential explanation for the identical oxygen isotope
compositions of the Earth and Moon. However, the mass fraction of the final
Moon that is derived from the inner disk is limited by resonant torques between
the disk and exterior growing moons. For initial disks containing < 2.5 lunar
masses (ML), we find that a final Moon with mass > 0.8ML contains < 60%
material derived from the inner disk, with this material preferentially
delivered to the Moon at the end of its accretion.
