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Date: | Thu, 29 Oct 1998 16:23:35 -0600 |
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Hi Thomas,
Try:
Stuart et al. 1991. Fractionation of the stable isotopes of oxygen and
carbon in carbon dioxide during the reaction of calcite with phosphoric
acid as a function of temerature and technique. Chemical Geology
(Isotope Geoscience Sect). 86:89-96.
For 90C, I have found their reported a=1.00798 works well. Note that
this value was measured in a common acid bath setup, which is what I was
using.
Cheers,
Geoff.
------------------------------------------------------------------------
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Geoff Koehler
Environment Canada Stable Isotope Laboratory
11 Innovation Bvld.
Saskatoon, SK, Canada
Telephone: (306)975-5778
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>-----Original Message-----
>From: Thomas Naehr [SMTP:[log in to unmask]]
>Sent: Thursday, October 29, 1998 4:06 PM
>To: [log in to unmask]
>Subject: fractionation between calcite and CO2
>
>Dear listmembers,
>
>I am looking for oxygen isotope fractionation factors between calcite and
>acid-liberated CO2 at temperatures above 25°C in order to correct d18O
>values of dolomite for differences in the dolomite-CO2 fractionation.
>
>So far I was only able to find a reliable fractionation factor for the
>calcite-CO2 system at 25°C (e.g., Kim & O'Neil 1997), which doesn't help me
>much because I would like to correct d18O values of dolomite reacted at
>75°C and 90°C.
>For dolomite I use an alpha dolomite-CO2 of 1.00976 at 75°C and 1.00931 at
>90°C according to Rosenbaum & Sheppard (1986). But what about calcite?
>Any suggestions?
>
>Thanks,
> Thomas
>
>
>_________________________________________________
>
>Thomas Naehr
>Monterey Bay Aquarium Research Institute (MBARI)
>P.O. Box 628
>7700 Sandholdt Road
>Moss Landing, California 95039
>
>Voice: (831) 775-1736 Fax: (831) 775-1620
>e-mail: [log in to unmask] http://www.mbari.org/~tnaehr
>_________________________________________________
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