good luck Roelant!
I have run a couple of dozen jarosites, in the 5-10 mg range. As sulfate vapors are a concern (they will liberate Ar occluded in the evaporated silicate on the walls of the crucible-oven assembly and create excessively old ages) we normally spend large amounts of time and labor to pre-clean the oven and minimize memory effects.
If you're looking at 10 ka ages, and you ran 10 Ma samples before, I suggest you invest time in a very thorough mechanical cleaning.
Purifying the Ar from the SO3 takes a bit longer, but the SAES C-50 can take it.
However, Paulo Vasconcelos has an immense experience with sulfates - take his word, more than mine!
Cheers
Igor
On 12.06.2019, at 15:59, Roelant van der Lelij <[log in to unmask]> wrote:
> Hello,
> We have a request for K-Ar geochronology of some (presumably) Holocene Jarosites.
> While we are able to resolve Holocene ages on our MS with satisfactory precision, I have no experience with Jarosite or sulfates.
> Could there be any risk regarding sulfate rich vapors in the extraction line / gas cleanup? We are talking quite a lot of material here - about ~100 mg.
> Cheers
> Roelant
> Geological Survey of Norway
>
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Igor M. Villa
Institut für Geologie
Baltzerstrasse 3
3012 BERN, Switzerland
Tel 0041 31 631 8777
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