Hi Dan,
Sorry for being out of touch. I have been in a bit of a tailspin since
Sheila passed away... just going through the motions of life. I am
thankful for work even if I am not giving it my all.
Say, Yvette Kuiper wrote to me, and I told her that I would forward her
questions to you. She got the idea to try some experiments with
monazite, and I told her that you are the authority, as far as I am
concerned. If we ever decide to try some of these things, I would sure
be happy to help, but I think some of the ideas are not very specific or
well formed at present.
You don't have to answer in great detail... maybe just a few comments to
start out.
Thanks; I hope you are well,
Mike
Here are the questions that she asked.
---
As you know, some of us geologists use in-situ U-Pb dating of monazite in thin section with clear textural relationships to date foliations and other microstructures. We assume that monazite grew during foliation development if the monazite is aligned with the foliation plane. I (and I am not alone) wonder how valid that assumption really is.
If a monazite was already there, and then the rock is foliated, would it look the same? Different in any way? If the monazite grows after the
foliation is already there, wouldn't it make sense for the monazite to grow along those foliation planes as opposed to overgrowing it,
considering it is a plane of weakness and perhaps an easy place for monazite to grow?
So I started talking about three experiments, first using equipment here at Mines in the metallurgy dpt (this whole idea really just started
while I was brainstorming with someone in metallurgy about something else), and then at Utrecht University, where they have a better setup
for this.
There would be three experiments:
1. Make an undeformed rock (schist/phyllite) with monazite in it (or just use a natural sample), then deform it
2. Add all ingredients (a powder?) and make the rock while deforming it
3. Make a deformed rock without monazite, then add fluids with dissolved monazite or something like that, and see where monazite would form
After that, we could just slice up the rocks and make thin sections to see where the monazite are and what they look like, or use more
sophisticated methods for 3D imaging, if available.
The High P-T lab at Utrecht University in the Netherlands may have a way to do it, but they ask me:
1) what P-T and H20 fugacity/pressure (if any) are needed to get monazite to form alongside the additional mineral assemblage that you want?
2) how quickly does monazite form under these conditions?
I think number 1 is a broad range of PT conditions and I am not sure about H2O fugacity. I also don't know how fast it would form. Would you
have an answer to these questions? I don't think there are simple phase diagrams for monazite, or are there?
I see Budzyn et al 2011, and Trail 2018, and Hetherington 2010, and more... but is there a simple 'recipe' to make monazite in schist or
phyllite in a lab? Do you think something like the experiments above may be possible given the right equipment? You probably have a good sense of this.
Cheers, Yvette
--
Michael L. Williams
Department of Geosciences
University of Massachusetts
Amherst, MA 01003
413-545-0745
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