Title: Chemical alteration patterns in metamict fergusonite
Abstract: A fergusonite sample from the Berere region in Madagascar was studied in detail with a wide range of analytical methods, including optical and scanning electron microscopy, transmission electron microscopy techniques, electron probe microanalysis and mapping, powder X-ray diffraction, and Raman, photoluminescence and infrared spectroscopy. The specimen contains high concentrations of actinide elements (U up to 6.9 wt%, Th up to 3.0 wt% as oxides) and, as a consequence, it is highly radiation-damaged. The sample has experienced intense, low- T chemical alteration through fluid-driven replacement reactions. The altered areas have sharp boundaries to their neighbouring host and are mainly located adjacent to large fractures. High-resolution element distribution maps show the complexity of the compositional changes. Altered areas are generally enriched in Si and Ca, and depleted in Y; however, most elements show variable trends and heterogeneous distribution patterns pointing to a non-uniform, presumably multi-step alteration history. Most remarkably, the actinides U and Th were comparably immobile; their concentrations having remained almost constant, being only mildly affected by the alteration reaction. This appears to support the potential suitability of the fergusonite-group minerals as host phases for the long-term immobilisation of nuclear waste.
Publication Year: 2010
Publication Date: 2010-04-22
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 15
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