Occurrence of selenium in sulfides from some sedimentary rocks of the western United States

Trace Elements Investigations 632
This report concerns work done on behalf of the Division of Raw Materials of the U.S. Atomic Energy Commission
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Investigations of the minor- and trace-element content of sulfides associated with uranium ore deposits from sandstone-type deposits have shown that selenium commonly substitutes for sulfur. The Morrison formation and Entrada sandstone of Jurassic age and the Wind River formation of Eocene age seem to be seleniferous stratigraphic zones; sulfides deposited within these formations generally contain abnormal amounts of selenium. The selenium content of the pyrite, marcasite, and chalcocite is much greater than that reported in previously published data.

Under the prevailing temperatures and pressures of formation of the Colorado Plateau uranium deposits the maximum amount of Se substituting for S in the pyrite structure was found to be 3 percent by weight. Ferroselite, the iron selenide (FeSe2), was found in two deposits on the Colorado Plateau and it was also established that galena (PbS) forms an isomorphous series with clausthalite (PbSe) in nature.

During oxidation of the selenium-bearing sulfides and selenides in the Colorado Plateau and Wyoming, the selenium forms pinkish crusts of either monoclinic or hexagonal native selenium intergrown with soluble sulfates, suggesting that under "normal" oxidizing conditions native selenium is more stable than selenites or selenates.

The above-normal selenium content of these sulfides from sedimentary rocks of Mesozoic and Tertiary age is significant. The high selenium in these sulfides is related to periods of volcanic and intrusive activity penecontemporaneous with the formation of the containing sediments.

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Publication type Report
Publication Subtype USGS Numbered Series
Title Occurrence of selenium in sulfides from some sedimentary rocks of the western United States
Series title Trace Elements Investigations
Series number 632
DOI 10.3133/tei632
Year Published 1956
Language English
Publisher U.S. Geological Survey
Description 54 p.
Country United States
State Arizona;Colorado;New Mexico;Utah;Wyoming
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