Correcting instrumental fractionation on 208Pb/206Pb and 232Th/238U

MartinGuitreau

Dear Iolite community,
I know that there are ways to obtain 208Pb/206Pb and 232Th/238U ratios out of Iolite but, as far as I know, this is essentially by dividing background-corrected signals on 206Pb, 208Pb, 232Th, and 238U ("Pb206_CPS", ...). However, these ratios are not corrected for instrumental elemental/isotopic fractionation. Is there an extension of the U-Pb Geochronology script that would allow 208Pb/206Pb and 232Th/238U to be treated like 207Pb/206Pb and 206Pb/238U? Most of the time, 232Th/238U is not significantly affected by downhole fractionation and could even be handled the same way as 207Pb/206Pb. Adding this routine would be great because we could use the 232/238 and 208/206 without having to correct it offline. Thank you for your time.
Best regards,
Martin

Bence

Hi @MartinGuitreau

We'll add that to the geochron DRS. It'll be available in an upcoming release of iolite.

I'll post here when it's complete.

-Bence

MartinGuitreau

Wonderful! Thank you so much, Bence.
Martin

Bence

Hi MartinGuitreau

Pb208/Pb206 and Th232/U238 have been added to the U-Pb Geochron DRS. It'll be available in the next release (v4.8).

These ratios are not calculated unless values for "208Pb/206Pb" and "232Th/238U" are recorded for the primary reference material. Note that the value in the RM file must be labelled exactly as above (i.e. "208Pb/206Pb", not "Pb208/Pb206" etc). The value for these ratios also cannot be 0.

If these values are not recorded in the RM file, the DRS will not calculate the associated channels so that the number and order of the output channels will remain the same for those that do not wish to calculate these values.

If you have any questions about the above, please let me know.

When v4.8 is released, please give it a try and let me know if you have any troubles.

-Bence