Origin of Graphitic Carbon and Pentlandite in Matrix Olivines in the Allende Meteorite
Adrian J. Brearley
Matrix olivines in the Allende carbonaceous chondrite are believed
to have formed by condensation processes in the primitive solar nebula.
However, transmission electron microscope observations of numerous
matrix olivines show that they contain abundant, previously unrecognized, nanometer-sized inclusions of pentlandite and poorly graphitized carbon. Neither of these phases would have been stable at
the high-temperature conditions required to condense iron-rich olivine
in the solar nebula. The presence of these inclusions is consistent
with formation of the olivines by parent body processes that involved
overgrowth of fine-grained organic materials and sulfides in the
precursor matrix materials.
Department of Earth and Planetary Sciences, University of New
Mexico, Albuquerque, NM 87131, USA. E-mail: brearley{at}unm.edu
