Origin of the El Dragón Selenium Mineralization, Quijarro Province, Potosí, Bolivia

A re-examination of the El Dragón selenium deposit in Potosí, Bolivia, reveals five distinct episodes of fault formation and mineralization spanning from 12 million years ago to the present. The study identified several new or near-endmember minerals, including petříčekite, krut’aite, penroseite, and a previously unknown copper-nickel-selenium mineral (CuNi₂Se₄). These findings suggest that highly oxidized, metal-rich fluids with exceptional selenium fugacities (log fSe₂ between −14.5 and −11.2) interacted with black shale and siltstone, leading to the deposition of selenium minerals. The source of selenium and associated metals likely originates from a neighboring Kupferschiefer-type black shale, rich in pyrite and organic matter, where reductive conditions facilitated selenate reduction and elemental selenium precipitation.

Grundmann, G., & Förster, H.-J. (2017). Origin of the El Dragón Selenium Mineralization, Quijarro Province, Potosí, Bolivia. Minerals, 7(5), 68. https://doi.org/10.3390/min7050068