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Oklo Mine, Franceville, Haut-Ogooué Province, Gabon

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Latitude & Longitude (WGS84): 1° 30' South , 13° 16' East
Latitude & Longitude (decimal): -1.5, 13.2666666667


This mine near the Mouana Mine is the site of over a dozen precambrian natural nuclear reactors. It is particularly known as the "Oklo phenomenon". Secondary enrichment of uranium oxides in cm to meter sized veins moderated by ground water consumed six tons of U-235 and elevated temperatures to a few hundred Celsius. This uranium isotope, normally standing for less than 1% of the uranium ore, is predicted to be at 3% level in Oklo in the beginning (now relatively strongly depleted). Remarkably the non-volatile fission products moved only a few cm in the veins during the last 1.5 billion years!

Gillberg-Wickmann (1983) points at Oklo as the only natural example of a significant isotope fractionaction between U-235 and U-238.

Meshik (2005) states, that (1) U-free Al phosphate minerals from the deposit concentrate the highest amount of xenon found in natural material; (2) once upon a time over 2 tons of plutonium 239 were generated within the deposit.

See also Bangombé, another natural nuclear reactor in the same area.

Mineral List


43 valid minerals.

Regional Geology

This information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This data will improve over time as more accurate maps and data sets are added.

Paleoproterozoic1600 - 2500 MaPaleoproterozoic intrusive and metamorphic terranes

Intrusive and metamorphic terranes

Mixtures of metamorphic and intrusive or plutonic rocks, tracts known as crystalline, migmatitic terranes, moderately to highly metamorphosed rocks of unknown origin with or without intrusions. This classification is inherently prone to variable interpretation, as other compilers might distinguish some packages by their metamorphic or gneissic protoliths, and the associated age ranges may be more variable.


References for regional geology:

Data provided by Macrostrat.org

Geological Survey of Canada. Generalized geological map of the world and linked databases. doi:10.4095/195142. Open File 2915d.



The above list contains all mineral locality references listed on mindat.org. This does not claim to be a complete list. If you know of more minerals from this site, please register so you can add to our database. This locality information is for reference purposes only. You should never attempt to visit any sites listed in mindat.org without first ensuring that you have the permission of the land and/or mineral rights holders for access and that you are aware of all safety precautions necessary.

References

- Econ Geol 84 (1989) 2286-2295.
- Radiochimica Acta 66/67 (1994) 455-461.
- Dymkov, Y., Holliger, P., Pagel, M., Gorshkov, A., and Artyukhina, A. (1997): Characterization of a La-Ce-Sr-Ca aluminous hydroxy phosphate in nuclear zone 13 in the Oklo uranium deposit (Gabon). Mineralium Deposita 32, 617-620.
- Janeczek, J. (1999): Mineralogy and geochemistry of natural fission reactors in Gabon. Reviews in Mineralogy and Geochemistry, 38, 321-392.
- Meshik, A. P. (November 2005): "The Workings of an Ancient Nuclear Reactor". Scientific American
- Hidaka, H. (2007): Geochemical characteristics of an ancient nuclear reactor "Oklo". Journal of Nuclear and Radiochemical Sciences 8, 99-103.



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