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Mobility of uranium during weathering

1997; Mineralogical Society of America; Volume: 82; Issue: 9-10 Linguagem: Inglês

10.2138/am-1997-9-1006

1945-3027

Takashi Murakami, Toshihiko Ohnuki, Hiroshi Isobe, Tsutomu Satō,

Geochemistry and Geologic Mapping

Other| October 01, 1997 Mobility of uranium during weathering Takashi Murakami; Takashi Murakami University of Tokyo, Mineralogical Institute, Tokyo, Japan Search for other works by this author on: GSW Google Scholar Toshihiko Ohnuki; Toshihiko Ohnuki Search for other works by this author on: GSW Google Scholar Hiroshi Isobe; Hiroshi Isobe Search for other works by this author on: GSW Google Scholar Tsutomu Sato Tsutomu Sato Search for other works by this author on: GSW Google Scholar American Mineralogist (1997) 82 (9-10): 888–899. https://doi.org/10.2138/am-1997-9-1006 Article history first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Takashi Murakami, Toshihiko Ohnuki, Hiroshi Isobe, Tsutomu Sato; Mobility of uranium during weathering. American Mineralogist 1997;; 82 (9-10): 888–899. doi: https://doi.org/10.2138/am-1997-9-1006 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu nav search search input Search input auto suggest search filter All ContentBy SocietyAmerican Mineralogist Search Advanced Search Abstract Mineralogical and geochemical mechanisms of U fixation under oxidizing conditions in the vicinity of the secondary U ore deposit at Koongarra, Australia, were examined using transmission and scanning electron microscopy and thermodynamic calculations. The formation of saleeite, Mg(UO2)2 (PO4)2·10H2O, is the predominant mechanism for U fixation upstream from the deposit, where saléeite replaces sklodowskite and granular apatite. Within the deposit and further downstream, U is fixed in microcrystals (10–50 nm) of saléeite and (meta)torbernite scattered within veins of fine-grained (2–50 nm) Fe3+ minerals (primarily goethite and hematite). Thermodynamic calculations indicate the groundwater is undersaturated with respect to saléeite and metatorbernite and that these minerals should precipitate at higher U or P concentrations than observed. This suggests that the upstream saléeite precipitated at the reaction interfaces of dissolving sklodowskite and apatite under local saturation conditions. Observed textural relationships of saléeite and (meta)torbernite microcrystals with the Fe minerals, combined with thermodynamic calculations, suggest surface precipitation as the formation mechanism for saléeite and (meta)torbernite microcrystals within, and downstream from, the secondary ore deposit. Phosphorous released during the aging of ferrihydrite and U adsorbed onto Fe minerals are probably the sources of the major components of the microcrystals. Downstream, the microcrystals exist where groundwater U concentrations are as low as 10–30 μg/L. Once released from the ore deposit, U is fixed in uranyl phosphates even where measured groundwater is undersaturated with respect to uranyl phosphates. The surface precipitation is an important example of long-term post-adsorption U fixation in a natural system. The fully crystalline and radiation-damaged microstructures of saléeite indicate uranyl phosphates have formed continuously (or intermittently) for the last few million years. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not currently have access to this article.