TY - JOUR
T1 - Uranium scavenging during mineral replacement reactions
AU - Li, Kan
AU - Pring, Allan
AU - Etschmann, Barbara
AU - Macmillan, Edeltraud
AU - Ngothai, Yung
AU - O'Neill, Brian
AU - Hooker, Anthony
AU - Mosselmans, Fred
AU - Brugger, Joel
PY - 2015
Y1 - 2015
N2 - Interface coupled dissolution-reprecipitation reactions (ICDR) are a common feature of fluid-rock interaction during crustal fluid flow. We tested the hypothesis that ICDR reactions can play a key role in scavenging minor elements by exploring the fate of U during the experimental sulfidation of hematite to chalcopyrite under hydrothermal conditions (220-300 °C). The experiments where U was added, either as solid UO2+x(s) or as a soluble uranyl complex, differed from the U-free experiments in that pyrite precipitated initially, before the onset of chalcopyrite precipitation. In addition, in UO2+x(s)- bearing experiments, enhanced hematite dissolution led to increased porosity and precipitation of pyrite+magnetite within the hematite core, whereas in uranyl nitrate-bearing experiments, abundant pyrite formed initially, before being replaced by chalcopyrite. Uranium scavenging was mainly associated with the early reaction stage (pyrite precipitation), resulting in a thin U-rich line marking the original hematite grain surface. This "line" consists of nanocrystals of UO2+x(s), based on chemical mapping and XANES spectroscopy. This study shows that the presence of minor components can affect the pathway of ICDR reactions. Reactions between U- and Cu-bearing fluids and hematite can explain the Cu-U association prominent in some iron oxide-copper-gold (IOCG) deposits.
AB - Interface coupled dissolution-reprecipitation reactions (ICDR) are a common feature of fluid-rock interaction during crustal fluid flow. We tested the hypothesis that ICDR reactions can play a key role in scavenging minor elements by exploring the fate of U during the experimental sulfidation of hematite to chalcopyrite under hydrothermal conditions (220-300 °C). The experiments where U was added, either as solid UO2+x(s) or as a soluble uranyl complex, differed from the U-free experiments in that pyrite precipitated initially, before the onset of chalcopyrite precipitation. In addition, in UO2+x(s)- bearing experiments, enhanced hematite dissolution led to increased porosity and precipitation of pyrite+magnetite within the hematite core, whereas in uranyl nitrate-bearing experiments, abundant pyrite formed initially, before being replaced by chalcopyrite. Uranium scavenging was mainly associated with the early reaction stage (pyrite precipitation), resulting in a thin U-rich line marking the original hematite grain surface. This "line" consists of nanocrystals of UO2+x(s), based on chemical mapping and XANES spectroscopy. This study shows that the presence of minor components can affect the pathway of ICDR reactions. Reactions between U- and Cu-bearing fluids and hematite can explain the Cu-U association prominent in some iron oxide-copper-gold (IOCG) deposits.
KW - Experiment
KW - Interface coupled dissolution-reprecipitation reactions
KW - IOCG deposits
KW - Scavenging
KW - Sulfidation reaction
KW - Uranium
UR - http://www.scopus.com/inward/record.url?scp=84939493087&partnerID=8YFLogxK
U2 - 10.2138/am-2015-5125
DO - 10.2138/am-2015-5125
M3 - Article
SN - 0003-004X
VL - 100
SP - 1728
EP - 1735
JO - American Mineralogist
JF - American Mineralogist
IS - 8/9
ER -