  Recent studies of chondrites have found a tungsten isotopic anomaly between
chondrules and matrix. Given the refractory nature of tungsten, this implies
that W was carried into the solar nebula by at least two distinct families of
pre-solar grains. The observed chondrule/matrix split requires that the
distinct families were kept separate during the dust coagulation process, and
that the two families of grain interacted with the chondrule formation
mechanism differently. We take the co-existence of different families of solids
in the same general orbital region at the chondrule-precursor size as given,
and explore the requirements for them to have interacted with the chondrule
formation process at significantly different rates. We show that this sorting
of families of solids into chondrule and matrix destined dust had to have been
at least as powerful a sorting mechanism as the relative settling of
aerodynamically distinct grains at at least two scale heights above the
midplane. The requirement that the chondrule formation mechanism was correlated
in some fashion with a dust grain sorting mechanism argues strongly for
spatially localized chondrule formation mechanisms such as turbulent
dissipation in non-thermally ionized disk surface layers, and argues against
volume filling mechanisms such as planetesimal bow shocks.
