Hostname: page-component-78c5997874-s2hrs Total loading time: 0 Render date: 2024-11-17T19:25:49.006Z Has data issue: false hasContentIssue false
  • English
  • Français

Characterization of U-Series Disequilibria at the Pena Blanca Natural Analogue Site, Chihuahua, Mexico

Published online by Cambridge University Press:  10 February 2011

Virgina Wong ,
Philip C. Goodell  and
Elizabeth Y. Anthony
Virgina Wong
Affiliation:
Department of Geological Sciences, University of Texas at El Paso, El Paso, TX 79968–0555
Philip C. Goodell
Affiliation:
Department of Geological Sciences, University of Texas at El Paso, El Paso, TX 79968–0555
Elizabeth Y. Anthony
Affiliation:
Department of Geological Sciences, University of Texas at El Paso, El Paso, TX 79968–0555
Get access

Abstract

The purpose of this study was to evaluate radionuclide migration from a uranium-mineralized breccia pipe. The site provides an excellent opportunity to evaluate radionuclide mobility in a geochemical environment similar to that around the proposed high-level waste repository at Yucca Mountain, Nevada. Samples represent fracture-infillings from both within and outside the breccia pipe. Mineral assemblages within the fractures include 1) pure kaolinite, 2) a mixture of ironoxyhydroxides (goethite and hematite) with associated alunite and jarosite, which we refer to as the Fe-mineral assemblage, and 3) carbonates. Uranophane, weeksite, soddyite, and boltwoodite are associated with samples from within the breccia zone.

We obtain radionuclide activities from gamma-ray rather than alpha spectroscopy, and the methodology for these measurements is presented in detail. Plots of 230Th/238U vs. 226Ra/230 Th show three distinct mobility trends. 1) The majority of the Fe-mineral samples from within the breccia pipe yield values between 1.0 and 1.1 for both ratios, 2) Fe-mineral samples from outside the ore zone and a kaolinite from within the ore zone have 230Th/ 238U of 0.58 to 0.83 and 226Ra/230Th of 1.09 to 1.42, and 3) some Fe-mineral samples from within the breccia pipe have values of 1.2 and 0.9 respectively. These data, combined with those from other studies at Peña Blanca suggest that U and Ra are sometimes mobile in the near-surface environment and that multiple episodes of enrichment and leaching are required to explain the trends.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 556: Symposium QQ – Scientific Basis for Nuclear Waste Management XXII , 1999 , 801
Copyright
Copyright © Materials Research Society 1999

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. Alba, L.A. and Chavez, R., Isochron West 10, 21 (1974).Google Scholar
2. Pearcy, E.C., Prikryl, J.D., Murphy, W.M., Leslie, B.W., Appl. Geochem. 9, 713 (1994).Google Scholar
3. Pickett, D. A. and Murphy, W.M. in Seventh EC Natural Analogue Working Group Meeting Proceedings, edited by Maravic, H. von and Smellie, J. (EUR 17851 EN, European Commission, Luxembourg, 1997) pp. 113–122.Google Scholar
4. Schwarcz, H.P., Gascoyne, M., Ford, D.C., Chem. Geol. 36, 87 (1982).Google Scholar
5. Ivanovich, M., Latharn, A.G., Longworth, G., Gascoyne, M., in Urlanium Series LDisequilihrium: Applications to Earth, Marine, and Environmental Sciences, edited by Ivanovich, M. and Harmon, R.S. (Clarendon Press, Oxford, 1992), pp. 583–630.Google Scholar
6. Murray, A.S., Marten, R., Johnston, A., Martin, P., J. Radioanal. Nucl. Chem. 115, 263 (1987).Google Scholar
7. Papp, Z., Dezso, Z., Daroczy, S., J. Radioanal. Nucl. Chem. 222, 171 (1997).Google Scholar
8. Cutshall, N.H., Larsen, I.L., Olsen, C.R., Nucl. Inst. Methods 206, 309 (1983).Google Scholar
9. Erdtmann, G. and Soyka, W., The Gamma Rays of the Radionuclides (Verlag Chemie, Weinheim, New York, 1979).Google Scholar
10. Pickett, D.A., Prikryl, J.D, Murphy, W. M., Pearcy, E.C., Appl. Geochem. (in review)Google Scholar
11. Murrell, M.T., Goldstein, S. J., Dixon, P.R., EOS Trans. AGU 78 (46), F788 (1997).Google Scholar
12. Gascoyne, M. and Schwarcz, H.P., Chem. Geol. 59, 75 (1986).Google Scholar