Scandium silicates from the Baveno and Cuasso al Monte NYF-granites, Southern Alps (Italy): Mineralogy and genetic inferences
-
F. Pezzotta
,
V. Diella
Abstract
A chemical and paragenetic study has been performed on Sc silicates and Sc-bearing beryl occurring in Hercynian NYF-miarolitic pink granite and granophyric leucogranite at Baveno and Cuasso al Monte, Western Southern-Alps, Italy. In the Baveno and Cuasso al Monte plutons, detailed field work allowed the discovery of a significant number of crystals of bazzite, thortveitite, scandiobabingtonite, cascandite, and jervisite representative of all the known morphological and color varieties of these minerals in the two localities. Other studied samples belong to the historic collections of the Natural History Museum of Milan.
Except for beryl, which crystallizes relatively early in aplitic granophyre, all the other Sc minerals crystallize as late-stage phases in cavities associated with fluorite. Chemical analyses reveal moderate Sc enrichment at the rim of beryl crystals. Bazzite displays a relatively large chemical variation, from .primitive. compositions enriched in Fe2O3 and Al2O3, to .highly evolved. compositions with values of Sc2O3 up to 17.54 wt%. Scandiobabingtonite shows a perfect inverse correlation between Fe3+ and Sc concentrations, suggesting complete solid solution between babingtonite and its Sc analogues. A wide variety of compositions have been determined for cascandite, significantly extending the compositional range of this mineral. In particular, the MnO content ranges from 0.37 to 4.87 wt%. The jervisite crystals analyzed in this work have rather homogeneous compositions much closer to the end-member if compared with the holotype analysis reported in literature. Thortveitite shows a wide range of compositions with variation in Sc2O3, Y2O3, HREE, and Fe2O3. Significant Fluctuations of the Sc/Yb ratios are in agreement with similar complex variations in the ratios between REE (e.g., Y/Dy) reported in the literature for crystals of gadolinite-group minerals from the same localities.
Two different genetic models are discussed to explain the precipitation of Sc silicates as late stage phases in cavities. (1) during the latest stages of magma crystallization, HFSE and Sc were extracted from the silicate liquid and partitioned into fluids due to the complexing effect of F. Indeed, in view of the NYF geochemistry of the granite and the significant abundance of the associated F-bearing minerals, Fluorides (but not other complexing agents such as carbonates and phosphates) played the major role in concentrating HFSE and Sc. In cavities, such elements resulted in a series of rare accessory phases when F was extracted from Fluids because of the precipitation of zinnwaldite and Fluorite. (2) HFSE, Sc, and Y+REE were mainly incorporated by gadolinite-(Y) and siderophyllite crystallizing from residual magma. Many of the accessory phases crystallized in cavities because of the aggressive effect of subcritical hydrous, F-rich Fluids on the previously formed gadolinite-(Y) (liberating REE, Y, B, Be, Fe, Ca), siderophyllite (liberating Fe, Ti, and possibly Nb-Ta, Sc, etc.), and feldspars (liberating Ca, P, Cs, Ba). This second model is consistent with the widespread hydrothermal alteration of the Baveno and Cuasso al Monte granites and granophyres
© 2015 by Walter de Gruyter Berlin/Boston
Articles in the same Issue
- Crystal-size and shape distributions of magnetite from uncultured magnetotactic bacteria as a potential biomarker
- Tourmaline-bearing rocks in the Singhbhum shear zone, eastern India: Evidence of boron infiltration during regional metamorphism
- High-resolution transmission electron microscopy (HRTEM) study of the 4a and 6a superstructure of bornite Cu5FeS4
- Possible Fe/Cu ordering schemes in the 2a superstructure of bornite (Cu5FeS4)
- TEM-specimen preparation of cell/mineral interfaces by Focused Ion Beam milling
- Direct observation of spinodal decomposition in the magnetite-hercynite system by susceptibility measurements and transmission electron microscopy
- Thermodynamics of uranyl minerals: Enthalpies of formation of rutherfordine, UO2CO3, andersonite, Na2CaUO2(CO3)3(H2O)5, and grimselite, K3NaUO2(CO3)3H2O
- Mixing and ordering behavior in manganocolumbite-ferrocolumbite solid solution: A single-crystal X-ray diffraction study
- Structure change of MgSiO3, MgGeO3, and MgTiO3 ilmenites under compression
- Dehydration processes in the meta-autunite group minerals meta-autunite, metasaléeite, and metatorbernite
- Investigation of the martensitic-like transformation from Mg2GeO4 olivine to its spinel structure polymorph
- A high-temperature diffraction study of the solid solution CaTiOSiO4-CaTiOGeO4
- The vibrational spectrum of synthetic hydrogrossular (katoite) Ca3Al2(O4H4)3: A low-temperature IR and Raman spectroscopic study
- Structural characterization of biogenic Mn oxides produced in seawater by the marine bacillus sp. strain SG-1
- Investigation of smectite hydration properties by modeling experimental X-ray diffraction patterns: Part I. Montmorillonite hydration properties
- Synthesis and crystal-chemistry of alkali amphiboles in the system Na2O-MgO-FeO-Fe2O3- SiO2-H2O as a function of fO2
- Compositional zoning in sphalerite crystals
- Structure and the extent of disorder in quaternary (Ca-Mg and Ca-Na) aluminosilicate glasses and melts
- Makarochkinite, Ca2Fe42+Fe3+TiSi4BeAlO20, a new beryllosilicate member of the aenigmatite-sapphirine-surinamite group from the Ilʼmen Mountains (southern Urals), Russia
- Formation of lava stalactites in the master tube of the 1792-1793 flow field, Mt. Etna (Italy)
- Crystal-size distributions of garnets in metapelites from the northeastern Bushveld contact aureole, South Africa
- Early diagenetic origin of Al phosphate-sulfate minerals (woodhouseite and crandallite series) in terrestrial sandstones, Nova Scotia, Canada
- Scandium silicates from the Baveno and Cuasso al Monte NYF-granites, Southern Alps (Italy): Mineralogy and genetic inferences
- Letter. The effect of Fictive temperature on Al coordination in high-pressure (10 GPa) sodium aluminosilicate glasses
- Letter. α-PbO2-type nanophase of TiO2 from coesite-bearing eclogite in the Dabie Mountains, China
- Letter. Morphological characteristics of ordered kaolinite: Investigation using electron back-scattered diffraction
Articles in the same Issue
- Crystal-size and shape distributions of magnetite from uncultured magnetotactic bacteria as a potential biomarker
- Tourmaline-bearing rocks in the Singhbhum shear zone, eastern India: Evidence of boron infiltration during regional metamorphism
- High-resolution transmission electron microscopy (HRTEM) study of the 4a and 6a superstructure of bornite Cu5FeS4
- Possible Fe/Cu ordering schemes in the 2a superstructure of bornite (Cu5FeS4)
- TEM-specimen preparation of cell/mineral interfaces by Focused Ion Beam milling
- Direct observation of spinodal decomposition in the magnetite-hercynite system by susceptibility measurements and transmission electron microscopy
- Thermodynamics of uranyl minerals: Enthalpies of formation of rutherfordine, UO2CO3, andersonite, Na2CaUO2(CO3)3(H2O)5, and grimselite, K3NaUO2(CO3)3H2O
- Mixing and ordering behavior in manganocolumbite-ferrocolumbite solid solution: A single-crystal X-ray diffraction study
- Structure change of MgSiO3, MgGeO3, and MgTiO3 ilmenites under compression
- Dehydration processes in the meta-autunite group minerals meta-autunite, metasaléeite, and metatorbernite
- Investigation of the martensitic-like transformation from Mg2GeO4 olivine to its spinel structure polymorph
- A high-temperature diffraction study of the solid solution CaTiOSiO4-CaTiOGeO4
- The vibrational spectrum of synthetic hydrogrossular (katoite) Ca3Al2(O4H4)3: A low-temperature IR and Raman spectroscopic study
- Structural characterization of biogenic Mn oxides produced in seawater by the marine bacillus sp. strain SG-1
- Investigation of smectite hydration properties by modeling experimental X-ray diffraction patterns: Part I. Montmorillonite hydration properties
- Synthesis and crystal-chemistry of alkali amphiboles in the system Na2O-MgO-FeO-Fe2O3- SiO2-H2O as a function of fO2
- Compositional zoning in sphalerite crystals
- Structure and the extent of disorder in quaternary (Ca-Mg and Ca-Na) aluminosilicate glasses and melts
- Makarochkinite, Ca2Fe42+Fe3+TiSi4BeAlO20, a new beryllosilicate member of the aenigmatite-sapphirine-surinamite group from the Ilʼmen Mountains (southern Urals), Russia
- Formation of lava stalactites in the master tube of the 1792-1793 flow field, Mt. Etna (Italy)
- Crystal-size distributions of garnets in metapelites from the northeastern Bushveld contact aureole, South Africa
- Early diagenetic origin of Al phosphate-sulfate minerals (woodhouseite and crandallite series) in terrestrial sandstones, Nova Scotia, Canada
- Scandium silicates from the Baveno and Cuasso al Monte NYF-granites, Southern Alps (Italy): Mineralogy and genetic inferences
- Letter. The effect of Fictive temperature on Al coordination in high-pressure (10 GPa) sodium aluminosilicate glasses
- Letter. α-PbO2-type nanophase of TiO2 from coesite-bearing eclogite in the Dabie Mountains, China
- Letter. Morphological characteristics of ordered kaolinite: Investigation using electron back-scattered diffraction
