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Re: Acapulco



On Sat, 15 Feb 1997 RRRummler@aol.com wrote:

> Hello Everyone,
> 
>      Frank Stroik wrote:
> 
> >     The Acapulcoite parent body accreted bfore the H- chondrite 
> >parent body, and thus had more Al 26. This excess Al 26 decayed, and 
> >heated the Acapulcoite parent body to the point of obliterating the 
> >chondrules present, and restructuring all the major minerals in the 
> >parent asteroid. 
> >	This indicates that the parent body was smaller than the 
> >H-chondrite parent body.
> 
>      Frank, I have a question about your Feb. 13 "Acapulco" posting that
> mentioned something about the size of the Acapulcocite parent body.  How can
> one conclude just from the excess Al 26 present in an early-formed parent
> body, and its obliterating of the chondrules of the parent body, that the
> Acapulcocite parent body was smaller than the olivine-bronzite (H) chondrite
> parent body?  Is it because even the excess amount of Al 26 present in the
> Acapulcocite parent body would not have had enough time due to its short
> "lifespan" to change a large parent body on the scale seen in Acapulcocites?
>  Or is it because even a large amount of Al 26 could not change the
> chondrules as substantially as seen in Acapulcocites in a large parent body
> because the Al 26 would not have been powerful enough?
> 
> Thanks,
> Jens
> 
> 
Jens,
	You are close. You see, it is a time contraint. Since both the 
acapulcoite parent body, and the H-chondrite parent body formed close 
together, then they should have had the same ammount AL 26 incorporated into 
their 
matrix(it is assumed that all objects formed within a few million yrs of 
each other). So, since it was observed, that the acapulcoite parent body 
had been heated more rapidly, we must assume that, the parent body of the 
acapulcoites formed earlier, thus incorporating more Al 26. Now if the 
acapulcoite parent body was the same size, or larger than the H-chondrite 
parent body, then both would have similar metamprphic histories. Now in 
order to account for what is observed, it must be infered that, the 
acapulcoite parent body is smaller, based on the fact that it 
incorporated more Al 26. Smaller bodies accrete faster than large ones, 
so this would account for the heating seen in acapulcoites.
 Does this make sense? If not let me know.

Frank Stroik
References: