Date: Sat, 23 Jul 1994 15:47:44 -0400 (EDT)
Subject: Inquiry on REE-U-Th accessories
From: ESGREW@MAINE.MAINE.EDU
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X-Envelope-To: msa@sylvia.smith.edu
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In studying a highly magnesian phlogopite schist, we came across an
unusual (at least to us) suite of accessory phases. The major phases in the
schist are colorless sapphirine (with spinel inclusions) and kornerupine.
Pyrrhotite is one accessory mineral; it contains most of the iron in the rock.
Using EDS, we have identified zircon, monazite and xenotime. The zircon is
clouded with black inclusions; these turn out to be largely uraninite; a few
could be thorite. Uraninite (thorian) is also present in monazite.

We were wondering whether such suites have been reported elsewhere in
metamorphic rocks. We would welcome information from anybody who is
aware of a similar REE-U-Th suite, such as references to literature where
they have been described.

What must be a curiosity to mineralogists and petrologists could be a
nightmare to zirconologists and others using U-Pb isotopes for dating!

Thank you in advance.