Phosphate minerals represent the major host for transition metals and H2O in pegmatitic rocks, playing an essential geochemical role in the evolution processes of pegmatites. A good knowledge of their crystal chemistry is therefore necessary to better understand the genesis of pegmatites. Paravauxite is a mineral found in hydrothermal tin veins and granite pegmatites. Its ideal chemical formula is Fe2+Al2(PO4)2(OH)2·8H2O. Its crystal structure was solved and refined by Baur in 1969 on the basis of single-crystal X-ray diffraction data. This structure model appears to be consistent. However, due to the technical limitations of X-ray diffraction, the refinement only provided the isotropic displacement parameters, and the positions of nine independent proton sites were assigned but not refined. This led to a poor description of (the expected) complex H-bonding scheme in the paravauxite structure. In light of this, the crystal structure of a natural paravauxite was reinvestigated using electron microprobe analysis in wavelength dispersive mode (EPMA-WDS) and single-crystal neutron diffraction in an attempt to resolve these open questions.

On the complex H-bonding network in paravauxite, Fe2+Al2(PO4)2(OH)2 · 8 H2O / G.D. Gatta, P. Vignola, M. Meven. - In: ANNUAL REPORT ... / HEINZ MAIER-LEIBNITZ ZENTRUM ; FORSCHUNGS NEUTRONENQUELLE HEINZ MAIER-LEIBNITZ. - (2014), pp. 82-83. [10.14459/2015md1239870]

On the complex H-bonding network in paravauxite, Fe2+Al2(PO4)2(OH)2 · 8 H2O

G.D. Gatta
Primo
;
2014

Abstract

Phosphate minerals represent the major host for transition metals and H2O in pegmatitic rocks, playing an essential geochemical role in the evolution processes of pegmatites. A good knowledge of their crystal chemistry is therefore necessary to better understand the genesis of pegmatites. Paravauxite is a mineral found in hydrothermal tin veins and granite pegmatites. Its ideal chemical formula is Fe2+Al2(PO4)2(OH)2·8H2O. Its crystal structure was solved and refined by Baur in 1969 on the basis of single-crystal X-ray diffraction data. This structure model appears to be consistent. However, due to the technical limitations of X-ray diffraction, the refinement only provided the isotropic displacement parameters, and the positions of nine independent proton sites were assigned but not refined. This led to a poor description of (the expected) complex H-bonding scheme in the paravauxite structure. In light of this, the crystal structure of a natural paravauxite was reinvestigated using electron microprobe analysis in wavelength dispersive mode (EPMA-WDS) and single-crystal neutron diffraction in an attempt to resolve these open questions.
paravauxite; Fe2+Al2(PO4)2(OH)2 · 8 H2O, single-crystal neutron diffraction; H-bonding
Settore GEO/09 - Georisorse Miner.Appl.Mineral.-Petrogr.per l'amb.e i Beni Cul
2014
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/277673
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