期刊
AMERICAN MINERALOGIST
卷 100, 期 8-9, 页码 1728-1735出版社
MINERALOGICAL SOC AMER
DOI: 10.2138/am-2015-5125
关键词
Uranium; scavenging; IOCG deposits; experiment; sulfidation reaction; interface coupled dissolution-reprecipitation reactions
资金
- Institute for Mineral and Energy Resources (IMER)
- Australian Research Council [DP1095069]
- BHP Billiton
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 degrees 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.
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