  We report trace element analyses from mineral phases in chondrules from
carbonaceous chondrites (Vigarano, Renazzo and Acfer 187), carried out by laser
ablation inductively coupled plasma mass spectrometry. Results are similar in
all three meteorites. Mesostasis has Rare Earth Element (REE) concentrations of
10-20 x CI. Low-Ca pyroxene has light REE (LREE) concentrations near 0.1 x CI
and heavy REE (HREE) near 1 x CI respectively. Olivine has HREE concentrations
at 0.1-1 x CI and LREE around 10-2 x CI. The coarsest olivine crystals tend to
have the most fractionated REE patterns, indicative of equilibrium
partitioning. Low-Ca pyroxene in the most pyroxene-rich chondrules tends to
have the lowest REE concentrations. Type I chondrules seem to have undergone a
significant degree of batch crystallization (as opposed to fractional
crystallization), which requires cooling rates slower than 1-100 K/h. This
would fill the gap between igneous CAIs and type II chondrules. The
anticorrelation between REE abundances and pyroxene mode may be understood as
due to dilution by addition of silica to the chondrule melt, as in the gas-melt
interaction scenario of Libourel et al. (2006). The rapid cooling rate (of the
order of 1000 K/h) which seems recorded by low-Ca pyroxene, contrasted with the
more diverse record of olivine, may point to a nonlinear cooling history or
suggest that formation of pyroxene-rich chondrule margins was an event distinct
from the crystallization of the interior.
