Metamictization and complex chemistry are major obstacles to the crystal chemical characterization of natural allanites. To overcome these problems, allanites, Ca(REE)Fe²+Al₂Si₃O₁₂(OH), where REE = La, La-Ce, Ce, Nd, Sm, Eu, Gd, Er, Dy, Yb and Y have been synthesized hydrothermally from unbuffered and buffered oxide mixes at 500 to 650°C, 5.5 kbar (550 MPa), and 700 to 725°C, 4 kbar (400 MPa). Although allanite is readily synthesized, high yields are obtained only for allanite-(LREE) compositions, and end"member composition is obtained only for allanite-(La). Er and Yb ions are too small to substitute at the A(2) site in allanite, but a small amount can substitute at the VI~coordinated M(3) site. Fe²+ in the M(3) site favors LREE substitution, which supports the contention that allanite is Ce'selective. / Ph. D.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/37332 |
| Date | 06 February 2013 |
| Creators | Affholter, Kathleen |
| Contributors | Geological Sciences, Hewitt, David A., Bloss, F. Donald, Gibbs, Gerald V., Ribbe, Paul H., Speer, J. Alexander |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Dissertation, Text |
| Format | viii, 208 leaves, BTD, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
| Relation | OCLC# 17720573, LD5655.V856_1987.A335.pdf |
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