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80 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES
FIGURE 7.—Photomicrograph of thin section of "normal" part of the Segowlie, L6 crystalline
chondrite. Note the extreme integration of the chondrule (right), which is, however, finegrained
(as is part of the matrix above it) compared to the adjacent matrix. Length of section,
4.5 mm.
compositions of our eight L-chondrites with the
four H-chondrites described by Fredriksson, et al.
(1975, table 4) shows that they differ essentially
only in the FeO content; if normalized to the same
FeO content, the silicates seem identical within
analytical uncertainties.
Conclusion
Eight L-chondrites with different textures and
classifications are chemically and mineralogically
almost identical. This indicates a similar origin
from chemically the same parent material and by
the same processes, probably impact events.
The silicate compositions in these L-chondrites,
except for the FeO contents, are close to those of
four previously described H-chondrites (Fredriksson,
et al., 1975), and if normalized to the same iron
content, the silicates are chemically identical. Thus,
we imply a common parent material for H- and L-
(also LL-) chondrites. The essential difference
between the groups only lies in the amounts of iron
reduced and the portion of such produced metal
remaining. Chemically the parent material might
well have been close to the main semi-amorphous
silicates in the carbonaceous chondrites such as
Ivuna or Orgueil (Bostrom and Fredriksson, 1966).
Early impacts may have caused the chemical altera-