Hostname: page-component-78c5997874-xbtfd Total loading time: 0 Render date: 2024-11-19T22:07:43.948Z Has data issue: false hasContentIssue false
  • English
  • Français

Growth and Alteration of Uranium-Rich Microlite

Published online by Cambridge University Press:  10 February 2011

R. Gierí ,
R. J. Swope ,
E. C. Buck ,
R. Guggenheim ,
D. Mathys  and
E. Reusser
R. Gierí
Affiliation:
Department of Earth and Atmospheric Sciences, Purdue University, West Lafayette, IN 47907-1397, USA; [email protected]
R. J. Swope
Affiliation:
Department of Earth and Atmospheric Sciences, Purdue University, West Lafayette, IN 47907-1397, USA
E. C. Buck
Affiliation:
Chemical Technology Division, Argonne National Laboratory, Argonne, IL 60439, USA
R. Guggenheim
Affiliation:
SEM Laboratory, University of Basel, CH-4056 Basel, Switzerland
D. Mathys
Affiliation:
SEM Laboratory, University of Basel, CH-4056 Basel, Switzerland
E. Reusser
Affiliation:
Institute of Mineralogy and Petrography, ETH Zentrum, CH-8092 Zürich, Switzerland
Get access

Abstract

Uranium-rich microlite, a pyrochlore-group mineral, occurs in 440 Ma old lithium pegmatites of the Mozambique Belt in East Africa. Microlite exhibits a pronounced growth zoning, with a U-free core surrounded by a U-rich rim (UO2 up to 17 wt.%). The core exhibits conjugate sets of straight cracks (cleavage planes) which provided pathways for a late-stage U-enriched pegmatitic fluid which interacted with the U-free microlite to produce a distinct U enrichment along the cracks and led to the formation of the U-rich rim. Following the stage of U incorporation into microlite, a second generation of hydrothermal fluids deposited mica along the cleavage planes. Subsequent to these two hydrothermal stages, the host rock was uplifted and subjected to intense low-temperature alteration during which Na, Ca and F were leached from the microlite crystals. This alteration also led to a hydration of microlite, but there is no evidence of U loss. These low-temperature alteration effects were only observed in the U-rich rim which is characterized by a large number of irregular cracks which are most probably the result of metamictization, as indicated by electron diffraction images and powder X-ray patterns.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 608: Symposium QQ – Scientific Basis for Nuclear Waste Management XXIII , 1999 , 519
Copyright
Copyright © Materials Research Society 2000

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

1 Vance, E.R., Ball, C.J., Day, R.A., Smith, K.L., Blackford, M.G., Begg, B.D., and Angel, P.J., J. Alloys Comp. 213/214, 406 (1994).Google Scholar
2 Buck, E.C., Chamberlain, D.B., and Gieré, R., in Scientific Basis for Nuclear Waste Management XXII, edited by Wronkiewicz, D.J. and Lee, J.H. (Mater. Res. Soc. Proc. 556, Pittsburgh, PA 1999), p. 19–26.Google Scholar
3 Hogarth, D.D., Am. Mineral. 62, 403 (1977).Google Scholar
4 Brugger, J., Gieré, R.6, Graeser, S., and Meisser, N., Contrib. Mineral. Petrol. 127, 136 (1997).Google Scholar
5 Harker, A.B., in Radioactive Waste Forms for the Future, edited by Lutze, W. and Ewing, R.C., North-Holland, Amsterdam, 1988, pp. 335–392.Google Scholar
6 Ewing, R.C., Weber, W.J., and Clinard, F.W., Progr. Nucl. Energy 29(2), 63 (1995).Google Scholar
7 Cerny, P. and Ercit, T.S., in Lanthanides, tantalum and niobium, edited by Möller, P., Cerny, P., and Saupé, F., Springer, Berlin, 1989, pp. 27–79.Google Scholar
8 Lumpkin, G.R. and Ewing, R.C., in Scientific Basis for Nuclear Waste Management VIII, edited by Jantzen, C.H., Stone, J.A., and Ewing, R.C. (Mater. Res. Soc. Proc. 44, Pittsburgh, PA 1985), p. 647-654.Google Scholar
9 Pouchou, J.L. and Pichoir, F., Rech. Aérosp. 1984–3, 167 (1984).Google Scholar
10 Correia, J.M. Neves, Nunes, J.E. Lopes, and Lucas, D.B., Rev. Ciênc. Geol., Lourenço Marques, Série A 4, 35 (1971).Google Scholar
11 Knorring, O. Von and Fadipe, A., Bull. Minéral. 104, 496 (1981).Google Scholar
12 Lumpkin, G.R. and Ewing, R.C., Phys. Chem.Minerals 16, 2 (1988).Google Scholar
13 Lumpkin, G.R. and Ewing, R.C., Am. Mineral. 77, 179 (1992).Google Scholar
14 Lumpkin, G.R. and Ewing, R.C., Am. Mineral. 80, 732 (1995).Google Scholar
15 Lumpkin, G.R. and Ewing, R.C., Am. Mineral. 81, 1237 (1996).Google Scholar