Kate M. Campbell Shelly Kelly Yvonne Roebbert Stefan Weyer Rizlan Bernier-Latmani Thomas Borch Amrita Bhattacharyya 2017 <p><span>Historically, it is believed that crystalline uraninite, produced via the abiotic reduction of hexavalent uranium (U</span>^(VI)<span>) is the dominant reduced U species formed in low-temperature uranium roll-front ore deposits. Here we show that non-crystalline U</span>^(IV)<span>&nbsp;generated through biologically mediated U</span>^(VI)<span>&nbsp;reduction is the predominant U</span>^(IV)<span>&nbsp;species in an undisturbed U roll-front ore deposit in Wyoming, USA. Characterization of U species revealed that the majority (</span><span class="stix"><span class="stix">∼</span></span><span>58-89%) of U is bound as U</span>^(IV)<span>to C-containing organic functional groups or inorganic carbonate, while uraninite and U</span>^(VI)<span><span>&nbsp;</span>represent only minor components. The uranium deposit exhibited mostly<span>&nbsp;</span></span>²³⁸<span>U-enriched isotope signatures, consistent with largely biotic reduction of U</span>^(VI)<span><span>&nbsp;</span>to U</span>^(IV)<span>. This finding implies that biogenic processes are more important to uranium ore genesis than previously understood. The predominance of a relatively labile form of U</span>^(IV)<span><span>&nbsp;</span>also provides an opportunity for a more economical and environmentally benign mining process, as well as the design of more effective post-mining restoration strategies and human health-risk assessment.</span></p> application/pdf 10.1038/ncomms15538 en Nature Publishing Biogenic non-crystalline U(IV) revealed as major component in uranium ore deposits article