Crystal chemistry of Th in fluorapatite
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Abstract
Through the complementary use of single-crystal X-ray diffraction and X-ray absorption spectroscopy, we present in this paper the first direct results on the site occupancy of thorium in the fluorapatite structure and the structural distortion created by its substitution. Structure refinements based on single-crystal X-ray diffraction data from synthetic Th-doped fluorapatite indicates that Th substitutes almost exclusively in the M2 site. A single-crystal X-ray study of natural fluorapatite from Mineville, New York, also indicated that substituting heavy scatterers (including Th) are concentrated in the apatite M2 site, but definitive site assignments of specific elements were not possible. Extended X-ray absorption fine-structure spectroscopy (EXAFS) was used to probe the local structure of Th in the synthetic fluorapatite (single-crystal form) with a Th concentration of roughly 20 000 ppm, as well as Th in the natural Mineville fluorapatite (powder form) with a Th concentration of ~2000 ppm. The EXAFS fitting results also indicate that Th partitions into the M2 site and yield a ~0.05-0.08 Å decrease of average M2-O bond distances associated with local structure distortions that are not obtainable from single-crystal X-ray diffraction studies.
© 2015 by Walter de Gruyter Berlin/Boston
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Articles in the same Issue
- A mineralogical, geochemical, and microbiogical assessment of the antimony- and arsenic-rich neutral mine drainage tailings near Pezinok, Slovakia
- Luminescence of diamonds from metamorphic rocks
- Crystal chemistry of Th in fluorapatite
- Hydrogen-bond and cation partitioning in muscovite: A single-crystal neutron-diffraction study at 295 and 20 K
- Spectroscopic characterization of transition metal impurities in natural montebrasite/amblygonite
- An assessment of the potential benefits of ion implants as trace-element reference material for electron probe X-ray microanalysis: The case of invisible gold
- The incorporation of hydroxyl into zircon
- Association between phosphorus and iron oxides in manganese ores
- Equation of state of carbonated hydroxylapatite at ambient temperature up to 10 GPa: Significance of carbonate
- Monoclinic tridymite in clast-rich impact melt rock from the Chesapeake Bay impact structure
- Phase boundary between perovskite and post-perovskite structures in MnGeO3 determined by in situ X-ray diffraction measurements using sintered diamond anvils
- Hydrogenation of FeSi under high pressure
- Fe-Ti oxide-silicate (QUIlF-type) equilibria in feldspathoid-bearing systems
- In situ bubble vesiculation in silicic magmas
- First-principles calculation of the elastic moduli of sheet silicates and their application to shale anisotropy
- A new semi-micro wet chemical method for apatite analysis and its application to the crystal chemistry of fluorapatite-chlorapatite solid solutions
- New insight into the structural transformation of partially dehydroxylated pyrophyllite
- A 94-layer long-period mica polytype: A TEM study
- The crystal structure of stichtite, re-examination of barbertonite, and the nature of polytypism in MgCr hydrotalcites
- Vorlanite (CaU6+)O4—A new mineral from the Upper Chegem caldera, Kabardino-Balkaria, Northern Caucasus, Russia
- The structure of braitschite, a calcium rare earth borate
- Alteration of dehydrated schoepite and soddyite to studtite, [(UO2)(O2)(H2O)2](H2O)2
- A reinvestigation of smectite illitization in experimental hydrothermal conditions: Results from X-ray diffraction and transmission electron microscopy
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