"S.Singletary" wrote:
> Have a look at:
> Hsu, W., et al., 2000, High Time resolution by use of the 26Al chronometer
> in the multistage formation of a CAI (Earth and Planetary Science Letters,
> 182, p.15-29).
> They are indeed complicated little beasties.
I agree re: those "little beasties" :-)
Krot et al. describe accretionary rims around several CAIs in the
Allende CV3 chondrite. The accretionary rims in Allende are multi-
layered and these layers differ from one another in
- texture,
- mineralogy and
- mineral chemistry.
The different layers (innermost to outermost) consist of:
1) Either pyroxene needles + olivine + clumps of hedenbergite and
andradite (IA) or
2) Olivine "doughnuts" (IB) (i.e., crystals with central cavities).
3) II and III contain olivine plates and laths.
4) The final layer (IV) separating accretionary rims from the Allende
matrix occurs as clumps of andradite + hedenbergite surrounded by
salitic pyroxene needles.
=> Nepheline and Fe,Ni-sulfides are common constituents in all
layers.
Reference:
KROT A.N. et al. (2001) Forsterite-rich accretionary rims around
calcium-aluminum-rich inclusions from the reduced CV3 chondrite
Efremovka (MAPS 36-5, 2001, pp. 611-628).
Cheers,
Bernd
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