[meteorite-list] Correlation of Fa & Fs for ordinary chondrites

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From: Matson, Robert <ROBERT.D.MATSON_at_meteoritecentral.com>
Date: Thu Apr 22 10:29:54 2004
Message-ID: <AF564D2B9D91D411B9FE00508BF1C86901B4ED57_at_US-Torrance.mail.saic.com>

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Hi Jeff,

> The relationship that you found was documented in meteorites
> shortly after the first electron microprobes became available
>to meteorite researchers. The landmark paper was:

> KEIL K. and FREDRIKSSON K. (1964) The iron, magnesium, and calcium
> distribution in coexisting olivines and rhombic pyroxenes of
> chondrites. J. Geophys. Res. 69, 3487-3515. <snip>

Thanks for the link and the abstract excerpt -- I had hoped a petrologist
would
chime in on the subject, and I was not disappointed. :-) You wrote:

"This relationship is due to equilibrium partitioning of Fe and Mg between
olivine and pyroxene."

An empirical relationship, while useful, is certainly more valuable when
there is a chemical reaction explanation for the ratio. If anything useful
came of the exercise (for me, anyway), it was the clear indication from
the plotted points that the Fs/Fa plot does not have an origin at 0,0:
that Fs will still remain if Fa goes to zero. Of course, this is outside
the range of ordinary chondrites, but it does show that better results
can be obtained using an Fa = A*Fs + B formula than a simpler
Fa = A*Fs.

Cheers,
Rob

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<DIV><FONT color=#0000ff face=Arial size=2><SPAN class=471242520-12092003>Hi
Jeff,</SPAN></FONT></DIV>
<DIV><FONT color=#0000ff face=Arial size=2><SPAN
class=471242520-12092003></SPAN></FONT> </DIV>
<DIV><FONT color=#0000ff face=Arial size=2><SPAN class=471242520-12092003>>
</SPAN></FONT><FONT face="Courier New, Courier">The relationship that you found
was documented in meteorites<SPAN class=471242520-12092003><FONT color=#0000ff
face=Arial size=2> </FONT></SPAN></FONT></DIV>
<DIV><FONT face="Courier New, Courier"><SPAN class=471242520-12092003><FONT
color=#0000ff face=Arial size=2>> </FONT></SPAN>shortly after the first
electron microprobes became available<SPAN class=471242520-12092003><FONT
color=#0000ff face=Arial size=2> </FONT></SPAN></FONT></DIV>
<DIV><FONT face="Courier New, Courier"><SPAN class=471242520-12092003><FONT
color=#0000ff face=Arial size=2>></FONT></SPAN>to meteorite
researchers.  The landmark paper was:<BR><BR><SPAN
class=471242520-12092003><FONT color=#0000ff face=Arial size=2> <FONT
color=#000000 face="Courier New"
size=3>></FONT> </FONT></SPAN>K</FONT><FONT face="Courier New, Courier"
size=2>EIL</FONT><FONT face="Courier New, Courier"> K. and F</FONT><FONT
face="Courier New, Courier" size=2>REDRIKSSON</FONT><FONT
face="Courier New, Courier"> K. (1964) The iron, magnesium, and calcium<SPAN
class=471242520-12092003><FONT color=#0000ff face=Arial
size=2> </FONT></SPAN></FONT></DIV>
<DIV><FONT face="Courier New, Courier"><SPAN class=471242520-12092003><FONT
color=#0000ff face=Arial size=2>></FONT></SPAN> distribution in coexisting
olivines and rhombic pyroxenes of<SPAN class=471242520-12092003><FONT
color=#0000ff face=Arial size=2> </FONT></SPAN></FONT></DIV>
<DIV><FONT face="Courier New, Courier"><SPAN class=471242520-12092003><FONT
color=#0000ff face=Arial size=2>></FONT></SPAN> chondrites. <I>J. Geophys.
Res.</I> <B>69</B>, 3487-3515.</FONT><FONT size=2><FONT color=#0000ff><FONT
face=Arial><SPAN class=471242520-12092003> <FONT color=#000000
face="Courier New" size=3> <snip></FONT></SPAN></FONT></FONT></FONT></DIV>
<DIV><FONT size=2><FONT color=#0000ff><FONT face=Arial><SPAN
class=471242520-12092003></SPAN></FONT></FONT></FONT> </DIV>
<DIV><FONT size=2><FONT color=#0000ff><FONT face=Arial><SPAN
class=471242520-12092003><FONT color=#000000 face="Courier New" size=3><FONT
face=Arial size=2>Thanks for the link and the abstract excerpt -- I had hoped a
petrologist would</FONT></FONT></SPAN></FONT></FONT></FONT></DIV>
<DIV><FONT color=#0000ff><FONT face=Arial><SPAN class=471242520-12092003><FONT
color=#000000 face="Courier New"><FONT face=Arial size=2>chime in
</FONT></FONT></SPAN></FONT></FONT><FONT color=#0000ff><FONT face=Arial><SPAN
class=471242520-12092003><FONT color=#000000 face="Courier New" size=3><FONT
face=Arial size=2>on the subject, and I was not disappointed. :-)  You
wrote:</FONT></FONT></SPAN></FONT></FONT></DIV>
<DIV><FONT color=#0000ff><FONT face=Arial><SPAN
class=471242520-12092003></SPAN></FONT></FONT> </DIV>
<DIV><FONT color=#0000ff><FONT face=Arial><SPAN class=471242520-12092003><FONT
color=#000000 face="Courier New" size=3><FONT face=Arial size=2>"This
relationship is due to equilibrium partitioning of Fe and Mg
between</FONT></FONT></SPAN></FONT></FONT></DIV>
<DIV><FONT color=#0000ff><FONT face=Arial><SPAN class=471242520-12092003><FONT
color=#000000 face="Courier New" size=3><FONT face=Arial size=2>olivine and
pyroxene."</FONT></FONT></SPAN></FONT></FONT></DIV>
<DIV><FONT color=#0000ff><FONT face=Arial><SPAN
class=471242520-12092003></SPAN></FONT></FONT> </DIV>
<DIV><FONT face=Arial size=2><SPAN class=471242520-12092003>An empirical
relationship, while useful, is certainly more valuable when</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN class=471242520-12092003>there is a chemical
reaction explanation for the ratio.  If anything useful</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN class=471242520-12092003>came of the exercise
(for me, anyway), it was the clear indication from</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN class=471242520-12092003>the
</SPAN></FONT><FONT face=Arial size=2><SPAN class=471242520-12092003>plotted
points that the </SPAN></FONT><FONT face=Arial size=2><SPAN
class=471242520-12092003>Fs/Fa plot does not have an origin at
0,0:</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN class=471242520-12092003>that Fs will still
remain if Fa goes to zero.  Of course, this is
outside</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN class=471242520-12092003>the range of
ordinary chondrites, but it does show that</SPAN></FONT><FONT face=Arial
size=2><SPAN class=471242520-12092003> better results</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN class=471242520-12092003>can be obtained
using an Fa = A*Fs + B formula </SPAN></FONT><FONT face=Arial size=2><SPAN
class=471242520-12092003>than a simpler</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN class=471242520-12092003>Fa =
A*Fs.</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN
class=471242520-12092003></SPAN></FONT> </DIV>
<DIV><FONT face=Arial size=2><SPAN
class=471242520-12092003>Cheers,</SPAN></FONT></DIV>
<DIV><FONT face=Arial size=2><SPAN
class=471242520-12092003>Rob</SPAN></FONT></DIV>
<DIV> </DIV></BODY></HTML>

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Received on Fri 12 Sep 2003 04:57:44 PM PDT

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