Author Topic: Geological CPX/OPX thermo/barometers and accuracy of EPMA  (Read 1022 times)

DavidAdams

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Re: Geological CPX/OPX thermo/barometers and accuracy of EPMA
« Reply #15 on: October 27, 2021, 06:38:50 PM »
I am overall happy with my Amelia Albite but I have to re-polish every 6-9 months in my experience to remain happy.

I also have the best success with the Amelia Albite

Has anyone experience or thoughts on Sodalite?

I have a very good Brazilian sodalite that is homogeneous for Cl but not so great for Na or Si. Also to Probeman's point about beam sensitivity in sodalite, I have several grains mounted in my standard block some of which show very noticeable beam damage/sensitivity and others that are very robust and resilient under the same beam conditions. I suspect sodalite exhibits similar anisotropic sensitivity to the e-beam as apatite, but haven't tested that yet as I don't have access to EBSD where I am currently employed to check crystallographic orientations.  :-\
David Adams
The University of Auckland
Faculty of Science | School of Environment

sem-geologist

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Re: Geological CPX/OPX thermo/barometers and accuracy of EPMA
« Reply #16 on: October 29, 2021, 06:45:07 AM »
I don't know what origin sodalite we have, but I would not compare Na instability with F migration inside Apatite. In apatite the F migrates inside and is a reversible process (the F which initially migrates to deeper, partially homogenize/diffuses back to surface in a few weeks/moths). In Sodalite the Na escapes to Vacuum and is irreversible. The speeds of changes during probing are also complete different. Apatite is slow, where Sodalite is extremely fast (just enough of few nA·s for Na content to be halved, where Apatite-F can take hundreds of nA·s). In sense of Na-to-vacuum leak comparable to Sodalite is Gagarinite. Na in albite is clearly much much better binned and compared to those is extremely stable (at low current, and low beam density).

Where could I buy such Amelia Albite (Europe)?