Tedd Hadley writes
in message <9948.957460096@agamemnon>:
> "Allen & Diane Roy" writes
> in message <002c01bfb592$02ace080$c9ea0b3f@oemcomputer>:
> >
> > This is saying that the ratio of D/Di is homogenous throughout the
> > magma.
>
> How could they not be? Chemical processes do not distinguish
> between D/Di so there's no way they could get seperated.
>
> Are you suggesting that there is a force that seperates D & Di,
> or perhaps a force that creates a bunch of D over here and a
> bunch of Di over there? What is this force?
Allen Roy sent me a private response to this; however, I'd
like to keep this discussion on the group where there are
geologists that can correct me if I say something wrong.
Allen asserts that the process of melting may leave concentrations
of D & Di in seperate places and/or that physical forces moving
magma around may cause varying concentrations of the two elements
in seperate places.
I don't see how this is possible. First, let me repeat: chemical
and physical processes do not distinguish between D/Di. Therefore,
it stands to reason that the only way D/Di can become "seperated"
is due to pure chance motion of individual atoms (ignoring
the affects of isotope fractionatation, which the talk.origins
FAQ covers). Thus, arguing that an appreciable difference in
isotopic homogenity would result from pure chance is about like
arguing that a significant portion of the air molecules in this
room will, by chance, hug the left side of the room, leaving
those of us on the right gasping for air.
Alan also sent me a reference "Magma mixing in a collisional
setting: a case study from the Tertiary volcanism in Eastern
Rhodope Mountains,Bulgaria". However, this reference appears
to have nothing to do with isotopic homogeneity and instead
discusses inclusions and bands of different chemicals
and mineral compositions. No one is claiming that magma
is a homogenous mixture of chemicals and minerals.
However, if you're really talking about mixing two sources,
that's another story and that's adequately addressed by the
talk.origin FAQ ( http://www.talkorigins.org/faqs/isochron-dating.html)
under the section "Mixing of two sources".
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