The uncommon sodium rare-earth phosphate mineral vitusite-(Ce) (Na3RE(PO4)2) can be considered as the extreme product of sodium and rare-earth substitution i the apatite structure. Lesser amounts of substitution provide sodium and rare-earth-bearing apatites up to about 80 mol. % exchange; beyond th...
| Main Authors: | , , |
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.613.9407 http://www.minersoc.org/pages/Archive-MM/Volume_56/56-383-235.pdf |
| Summary: | The uncommon sodium rare-earth phosphate mineral vitusite-(Ce) (Na3RE(PO4)2) can be considered as the extreme product of sodium and rare-earth substitution i the apatite structure. Lesser amounts of substitution provide sodium and rare-earth-bearing apatites up to about 80 mol. % exchange; beyond this point vitusite is the stable phase. The structure of vitusite, determined previously from a synthetic analogue, can also be considered as a derivative from apatite, but with cations exchanged on sites normally occupied by anions. Vitusite can therefore be considered as a sodium- and rare-earth-rich apatite nd-member, with a distinct, but apatite-derived, structure, formed in highly persodic and high rare-earth environments. From an examination of the literature on diffusion in apatite, vitusite in principle could be formed from apatite sensu stricto by subsolidus diffusion in response to late-stage Na-and RE-rich hydrothermal fluids. |
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