Primitive chondrite components in six carbonaceous chondrites, Bencubbin, HaH 237, Gujba,
Isheyevo, Acfer 209 and Acfer 094 were studied to examine the complex thermal histories of
individual particles. Significant information about the origin and evolution of the solar nebula is
contained within primitive chondrite components including FeNi metals, sulphides, matrix material
and calcium aluminium inclusions, allowing conclusions to be drawn about the conditions
which prevailed in the early nebula.
This thesis describes the analysis of meteoritic metal and other components in carbonaceous
chondrites using a suite of complementary techniques including secondary electron microscopy
(SEM), transmission electron microscopy (TEM), electron backscatter diffraction (EBSD), secondary
ion mass spectrometry (nanoSIMS), grain-size frequency distribution (GSFD) and computed
tomography. Metal is chosen as the primary comparative component as it is a common
feature in carbonaceous chondrites and is an indication of the extent to which a sample has been
exposed to thermal, metamorphic and alteration processes.
EBSD results reveal a variation between chondrule-associated metal and matrix metal in CR
chondrite Acfer 209 and the ungrouped chondrite Acfer 094 indicating a difference in formation
and subsequent processing. TEM results demonstrated that evidence for aqueous alteration
occurs on a sub-μm scale on the rims of FeNi metal grains in Acfer 094. FeNi metallic rims
displayed regions of pitting corrosion and an enrichment in O and Ni accompanied by depletion
in Fe. These features indicate interaction with an aqueous fluid.
Grain-size frequency distribution analyses revealed a strong and common mode in the metal
grain aspect ratios of three samples from the CB group of chondrites indicating a common deformational
event. The presence of adjacent primitive components with varying chemical and
crystallographic textures reveals that these samples were subject to a complex thermal history.
Fine-grained matrix material in HaH 237 is heavily hydrated and shows no complementarity
to chondrules which escaped aqueous alteration consistent with the X-wind model. In contrast,
matrix material does show compositional complementarity to chondrules in Acfer 094 and
Acfer 209. This suggests material for both components formed in the same region of a nebula
conforming to the shock model where material formed on the disk.