2 research outputs found
Abundance, Major Element Composition and Size of Components and Matrix in CV, CO and Acfer 094 Chondrites
The relative abundances and chemical compositions of the macroscopic
components or "inclusions" (chondrules and refractory inclusions) and
fine-grained mineral matrix in chondritic meteorites provide constraints on
astrophysical theories of inclusion formation and chondrite accretion. We
present new techniques for analysis of low count per pixel Si, Mg, Ca, Al, Ti
and Fe x-ray intensity maps of rock sections, and apply them to large areas of
CO and CV chondrites, and the ungrouped Acfer 094 chondrite. For many thousands
of manually segmented and type-identified inclusions, we are able to assess,
pixel-by-pixel, the major element content of each inclusion. We quantify the
total fraction of those elements accounted for by various types of inclusion
and matrix. Among CO chondrites, both matrix and inclusion Mg to Si ratios
approach the solar (and bulk CO) ratio with increasing petrologic grade, but Si
remains enriched in inclusions relative to matrix. The oxidized CV chondrites
with higher matrix-inclusion ratios exhibit more severe aqueous alteration
(oxidation), and their excess matrix accounts for their higher porosity
relative to reduced CV chondrites. Porosity could accommodate an original ice
component of matrix as the direct cause of local alteration of oxidized CV
chondrites. We confirm that major element abundances among inclusions differ
greatly, across a wide range of CO and CV chondrites. These abundances in all
cases add up to near-chondritic (solar) bulk abundance ratios in these
chondrites, despite wide variations in matrix-inclusion ratios and inclusion
sizes: chondrite components are complementary. This "complementarity" provides
a robust meteoritic constraint for astrophysical disk models