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CEMENTING PROCESS

Martin wrote to Matt:

One last question, how does the  c e m e n t i n g  process work in
meteorites such as the brecciation difference between Peekskill and
Bison.

LU J. (1992) Chondrules formed through  c e m e n t a t i o n  of
mineral clusters by feldspathic melts (Meteoritics 27-3, 1992, A252 -
Excerpt):

Although the olivine compositions and textures are similar to the relic
grains described by Nagahara (1983), the association of "incompatible"
phenocrysts (Random House Webster: phenocryst = any of the conspicuous
crystals in a porphyritic rock) and melts in these unusual chondrules
suggests that they were formed through  c e m e n t a t i o n  of
unmelted mineral clusters by non co-genetic melts. Considering the high
CaO contents of group Al and A2 chondrules, the viscosity of the melts
must be much lower than the SiO2-rich melts of group B1 chondrules. lt
is therefore possible that some of these low viscosity melts may spin
off from their host droplets and cement the FeO-rich mineral clusters in
the vicinity. The presence of these unusual chondrules suggests that
chondrule-forming processes were very dynamic and that while most
chondrules were formed through in situ melting of pre-existing solid
material, possibly accompanied by reduction and volatilization, some
chondrules could have been formed through c e m e n t a t i o n  of
unmelted mineral clusters by feldspathic melts.

Regards, Bernd