Dear Darren and others,

We spent considerable time working with NBS-30 on the 
TC-EA.  It is published in our paper on the method for 
measuring hydrogen isotope ratios in water and solids. 
 The PDF version is at

http://epswww.unm.edu/facstaff/zsharp/hydromethod.pdf

There is 5 wt % water in NBS-30, more than what would be 
expected from a normal biotite.  There is probably some 
late-stage chlorite lamellae in the sample, but it is not 
a problem, as long as you realize that the water content 
is higher than a normal biotite.

The dD values of this sample should be quite reproducible 
if you operate at a high temperature.  At 1350oC - which 
is high enough for water - hydrous silicates will not give 
reproducible results.

As for the oxygen, about 16% of the oxygen is in the 
hydroxyl site.  During dehydration, however, only half of 
the water comes off  (2(OH)-  -> H2O  + 1/2 O--).  In 
other words, you get all of the hydrogen out of the 
sample, but leave 50% of the oxygen behind for charge 
balance.  What actually happens is perhaps far more 
complicated.  There could be exchange of the oxygen 
between the tetrahedral/octahedral sites and the hydroxyl 
site.  So it's hard to know what's going on.

We tried to use the TC-EA to extract the hydroxyl water, 
but it gave us variable compositions.  It may be worth 
looking into again.

It would be wonderful to be able to get the d18O value of 
the hydroxyl oxygen, because there should be a 
fractionation between the oxgyen in the different sites 
that varies with temperature.

A number of authors have played around with this.  I

Check the following:

Bechtel, A., and Hoernes, S., 1990, Oxygen isotope 
fractionation between oxygen of different sites in illite 
minerals; a potential single-mineral thermometer: 
Contributions to Mineralogy and Petrology, v. 104, p. 
463-470.

Zheng, Y.-F., 1993, Calculation of oxygen isotope 
fractionation in hydroxyl-bearing silicates: Earth and 
Planetary Science Letters, v. 120, p. 247-263.

Delgado, A., and Reyes, E., 1996, Oxygen and hydrogen 
isotope compositions in clay minerals: a potential 
single-mineral geothermometer: Geochimica et Cosmochimica 
Acta, v. 60, p. 4285-4289.

Best wishes,

Zach

On Thu, 8 Feb 2007 10:52:41 -0500
  Darren Gröcke <[log in to unmask]> wrote:
> Dear Colleagues
> 
> Looking through the Isogeochem archives there was a 
>discussion back  in 2001 on the dD of NBS 30 (see one 
>such message below). We have  been analyzing NBS 30 here 
>using our TCEA and the results compared to  our other 
>internal and international standards are not very good. 
> Have I missed some vital information around the 
>community about  analyzing NBS 30 for dD and d18O using a 
>TCEA? We are getting good  results for dD but not for 
>d18O.
> 
> Thanks
> 
> Darren
> 
> 
>> Subject:
>> Re: delta D of NBS-30
>> From:
>> Willi A. Brand
>> Reply-To:
>> Stable Isotope Geochemistry <[log in to unmask]>
>> Date:
>> Mon, 10 Sep 2001 08:13:51 +0200
>> Content-Type:
>> text/plain
>>
>> Hi,
>> a number of years ago, during the early stages of high 
>>temperature
>> pyrolysis developments at Finnigan I ran NBS30 at the 
>>1-5-milligram
>> level and got astonishing results. I do not recall the 
>>exact  
>> numbers but
>> I had two distinct cluster values. My conclusion at the 
>>time was that
>> the material was not homogeneous at the single grain 
>>level and I
>> discontinued using it for the purpose. Has anyone 
>>experienced  
>> something
>> similar?
>> Willi
>> --
>> ‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰
>> Willi A. Brand, Stable Isotope Laboratory 
>>     [log in to unmask]
>> Max-Planck-Institute for Biogeochemistry
>> Carl-Zeiss-Promenade 10, 07745 Jena, Germany      Tel 
>>+49-3641-643718
>> P.O.Box 100164, 07701 Jena, Germany              Fax: 
>>+49-3641-643710
>> http://www.bgc-jena.mpg.de/pages/public/Iso+Gas-Lab/BGC_Gaslab.html
>> http://www.bgc-jena.mpg.de/pages/public/Iso+Gas-Lab/BGC_Isolab.html
>> ‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰‰
> 
> 
> Dr Darren Grocke
> Associate Professor & Director of SIBL
> 
> Stable-Isotope Biogeochemistry Laboratory (SIBL)
> McMaster University
> School of Geography & Earth Sciences
> 1280 Main Street West
> Hamilton, Ontario, L8S 4K1
> Canada
> 
> http://www.science.mcmaster.ca/geo/research/sibl/index.html
> Phone: 905 525 9140 ext. 26334
>Fax: 905 546 0463