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Redox states of uranium in samples of microlite and monazite

Puchkova E.V., Bogdanov R.V., Gieré R.
2 016
Short Citation: 
Puchkova et al., 2016
American Mineralogist
By applying the method of chemical shifts of the uranium Lα1 and Lβ1 X-ray emission lines, the oxidation state of U has been determined in select samples of microlite and monazite. From the relative contents of U4+, U5+, and U6+ species, the oxygen coefficients have been calculated as a characteristic of U-oxidation rate. It is shown that the oxidation state of U is higher in the studied microlite than in monazite. Possible mechanisms of U oxidation in these two types of minerals are discussed, and it appears that the crystal structure of monazite plays an important role in stabilizing the U redox state. Spontaneous purification of the monazite structure from alien atoms, including U, may be possible via recrystallization of the α-recoil tracks. An explanation is suggested for intensive U oxidation in microlite and in other minerals of the pyrochlore group.
EES Authors: 
Reto Gieré

Department of Earth and Environmental Science / University of Pennsylvania, 251 Hayden Hall, 240 South 33rd Street, Philadelphia, PA 19104-6316