Changes in the new UPb DRS (“U_Pb_Geochronology3”)

There are some noteworthy improvements in the latest release of the UPb DRS (U_Pb_Geochronology3), so I thought I should post a description of what’s changed.

One of the biggest changes is that flexibility has been added in which isotopes have been measured – previous versions required 206, 207, 208, 232, and 238 (with an option for 204). This meant that users (particularly those with Nu multicollectors) that had not measured all of these isotopes needed a modified version of the DRS. The DRS is now able to run with any combination of masses, with the only restriction being that 206Pb and 238U must be included.

Another change has been to improve the DRS’ ability to identify the names of the different masses measured, regardless of their input channel name. Again, this increased flexibility will hopefully mean that fewer users need to modify the DRS to get it to work with data from their machine (that said, because of complex collector arrays and the complications of .nrf files, users of Nu multi-collectors will probably still need to use a “shortcut” file).

Next, I took up the kind offer by Joe Petrus that 207Pb/206Pb ages be moved from the VizualAge add-on to the main UPb DRS. In addition to building in the age calculation I have also modified it so that it uses a lookup table instead of an iterative calculation. I was concerned that the iterative calculation was theoretically capable of producing spurious ages, whereas the lookup table should be immune to this problem. For those interested, the lookup table spans ages from 1 Ma to 4600 Ma, in increments of 0.1%. The age for a given 7/6 ratio is then read from the table using linear interpolation between these increments (which means the actual accuracy of the lookup table readouts will be much much better than 0.1%). The decay constants used in generating the lookup table are 9.8485E-10 (235U) and 1.55125E-10 (238U).

In addition to those big things, there were also some minor changes/fixes:

—A minor bug in the down-hole fitting window that meant that manually adjusting the fit parameters sometimes failed has been fixed.

—The 238/235 ratio used in calculations is now a Global Variable that can be viewed and edited via the Edit Settings window (for now it’s still the old accepted value of 137.88).

—The Global Variable that allowed setting the number of histogram bins has been removed to avoid clutter in the Edit Settings window (if anyone feels that it was useful I’d be happy to reinstate it, but I got the impression it wasn’t being used).

And as always, any questions or discussions are welcomed on the Iolite forum

Comments

  1. Hi Chad, Do you know if Joe has implemented the same improvements to “the DRS’ ability to identify the names of the different masses measured, regardless of their input channel name”? I ask because I have data that has already been successfully reduced using U_Pb_Geochronology3. When I try to switch to VizualAge, it gives me the error stating that I need to have 206 and 238 (which I do or else I wouldn’t have gotten very far with the U_Pb DRS). If I rename my U238O16 column in all my fin/fin2 files, to something that does not contain the string “238”, I can get VizAge to allow me to crunch. But that means starting all over and editing every single data file. Can you tell me how to make shortcut files for ElementXR data? Cheers, Sarah. PS I have tried to register on the Phorum, but it has been a few days now and still no activation email (nothing in my spam folder either).

  2. Hi Sarah,
    First of all, I’m not sure why you’re having trouble with the forum – we’ll try to figure out what’s going on there.
    As for VizualAge, your best bet is to ask Joe Petrus as I’m unfortunately not up to speed on what changes he’s made.
    I can give you one suggestion in the meantime though, which isn’t perfect but still beats changing each individual FIN2 file. If you import your entire session of data into Iolite then you can open the “Data Browser” (from the “Data” dropdown menu) and browse to “packages–>Iolite–>input” then you can change the name of the channel (e.g., change it from “U238O16” to “U238”) and make the same change to the “GlobalListOfInputChannels” string in the same folder. That will then in essence change all of the FIN2 files at once for that session – still a headache, but a lot quicker than doing it for each file individually…
    PS To change the string right-click and save full path, then paste into the history window (Ctrl+J) to give something like:
    root:Packages:iolite:input:GlobalListOfInputChannels = “Pb206;Pb207;…;”

    Cheers,
    Chad