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Geochemical Studies of Columbia River Basalts

Published online by Cambridge University Press:  25 February 2011

D. G. Brookins ,
M. T. Murphy ,
H. A. Wollenberg  and
S. Flexser
D. G. Brookins
Affiliation:
University of New Mexico, Albuquerque, NM 87131
M. T. Murphy
Affiliation:
University of New Mexico, Albuquerque, NM 87131
H. A. Wollenberg
Affiliation:
Lawrence Berkeley Laboratories, Berkeley, CA
S. Flexser
Affiliation:
Lawrence Berkeley Laboratories, Berkeley, CA
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Abstract

We report our findings for two studies of Columbia River basalts that are relevant to United States radwaste disposal programs. A rhyodacite intrudes the Wanapum basalt and is exposed in a quarry along the Hood River, Oregon. Since the rhyodacite is different geochemically from the basalt, and was intruded at a high temperature, then this site can be used to evaluate the effects of the intrusion on the basalt. In such a study we assume the intrusive rock is a high temperature heat engine, and that cooling may be by convection, conduction, or both. Contact effects of the intrusion are not pronounced in the basalt, and are restricted to minor recrystallization within one meter of the contact, and to possibly some minor fracture filling. Traverses were made from the rhyodacite into the basalt, and samples at closely spaced intervals analyzed for K, U, Th by field and laboratory gamma spectrometry, and by neutron activation analysis for some 35 elements. Separate aliquots were analyzed by isotope dilution to inspect Sr isotopic variations. The chemical studies do not indicate migration of any elements from the rhyodacite into the basalt, nor for any in-basalt or in-rhyodacite migration. Despite a pronounced chemical gradient between the rocks, each has remained a closed, isochemical system. The Sr isotopic studies indicate that the rhyodacite possesses Sr (87/86) = 0.70407 ± 0.00008 while the intruded basalts possess Sr (87/86) = 0.7052 ± 0.0002. Even in samples of the contact, with intermingled rhyodacite and basalt, each rock preserves its own characteristic Sr (87/86) signature, thus again attesting to the closed system conditions. We conclude for this natural experiment that the Wanapum basalt is not readily penetrated by elements from a high temperature, molten source.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 26: Symposium D – Scientific Basis for Nuclear Waste Management VII , 1983 , 917
Copyright
Copyright © Materials Research Society 1984

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References

REFERENCES

1. Brass, G. W., The sources of marine strontium and the 87Sr/86Sr ratio in the sea throughout Phanerozoic time: Unpub. Ph.D. dissertation, Yale Univ., 160 pp. (1973).Google Scholar
2. Brookins, D. G., Murphy, M. T., and Wollenberg, H. A., Strontium isotopic study of fracture filling minerals in the Grande Ronde Basalt, Washington: in Scientific Basis for Nuclear Waste Management, VII (McVay, G. L., Ed.), in press.Google Scholar
3. Carlson, R. W., Lugmair, G. W., and Macdougall, J. D., Geochim. Cosmochim. Acta 45, p. 2483–2500 (1981)CrossRefGoogle Scholar
4. Department of Energy, Site characterization report for the Basalt Waste Isolation Project: U.S. Dept. Energy Rpt. DOE/RL 82-3, vol. 1 (1982).Google Scholar
5. Drever, J. I., The geochemistry of natural waters: Prentice-Hall Pub. Co., NJ, 388 p. (1982).Google Scholar
6. Faure, G., Principles of Isotope Geology (Wiley-Interscience, New York, 1977), 460 p.Google Scholar
7. Haskin, L. A., Haskin, M. A., Frey, F. A., and Wildeman, T. R., Relative and absolute terrestrial abundances of the rare earths: in Origin and Distribution of the Elements (Pergamon Press, New York, 1968).Google Scholar
8. Myers, C. W., and Price, S. M., Geologic studies of the Columbia Plateau: A Status Report (RHO-BWI-ST-4, 1979).Google Scholar
9. Minor, M. M., Hensley, W. K., Denton, M. M., and Garcia, S. R., An automated activation analysis system: 1981 Int. Conf. on Modern Trends in Activation Analysis (Univ. Toronto, June 15-19, 1981) (1981), 12 p.Google Scholar