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Isotopic and TEM investigations of variations in
presolar graphite morphology.
Croat T. K., Stadermann F. J., and Bernatowicz T. J.
(2007)
Lunar Planet. Sci. XXXVIII, Abstract #1484.
ABSTRACT
As discovered during previous studies of Murchison
"onion" and "cauliflower" presolar graphites, the degree of
graphitization among presolar graphites is quite variable.
Along with these morphological variations (as described
below), corresponding isotopic/elemental trends have also
been seen (e.g. higher trace element content in more
turbostratic cauliflowers). These morphological variations
probably reveal differences in formation conditions, rather
than being ascribed to later processing or heating. For
example, changes in the rapidity of formation or in the
circumstellar chemical environment (e.g. C/O ratio in the
gas) could alter their degree of graphitization. From
correlated transmission electron microscopy (TEM) and
NanoSIMS isotopic investigations of the graphite
morphologies and their internal constituents, we hope to
learn more about the circumstellar environments in which
they formed. In this abstract, we look more narrowly at the
chemical and isotopic properties of turbostratic round
graphites (both "platy" and "scaly" morphologies).
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