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Stable Isotope Geochemistry

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Subject:
laser ablation for sulfate O
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Stable Isotope Geochemistry <[log in to unmask]>
Date:
Wed, 24 May 2006 05:41:51 +0200
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Dear Doug,

I tried smectites with laser ablation.

All the samples were dehydrated for 1 day at 200 C in order to clean for absorbtion and interlayer water. I  analyzed pure smectite samples (100%), which were not prepared chemicaly before. Also I analyzed separed smectites from soils. Results are the same for different samples: the d18O values are very, very low (??), and there are no reproductible data. 
I do not recommed prefluorination with BrF5 because, even the dehydrated smectites will react immediately, so I suspect that oxygen from OH or silicate positions is partly reacting.
A better way: classical silicate line where results are OK after cleaning for one day for interlayer and absorbtion at 200 C and fluorinating for at least 12 hours afterwards.

Ana-Voica Bojar
Dept. of Earth Sciences
Graz University, A-8010
Austria

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