Structure and properties of fluorine-bearing aluminosilicate melts: the system Na2O-Al2O3-SiO2-F at 1 atm

Mysen, Bjørn O.; Virgo, David

doi:10.1007/bf00413348

Cited by 144 publications

(128 citation statements)

References 34 publications

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“…Previous Raman-spectroscopic studies of highly polymerized aluminosilicate glasses (MYSEN and VIRGO, 1985a) showed evidence for depolymerization of the glass structure by F. This is consistent with our results which suggest removal of Al from the silicate network by complexing with F. However, this result does not necessarily apply to other glass compositions. Adding F to depolymerized melts might actually increase the degree of polymerization (FOLEY et al, 1986;LUTH 1988a,b).…”

Section: Discussionsupporting

confidence: 91%

“…MYSEN and VIRGO ( 1985a) reached the same conclusion. However, in their study of the joins Si02-AlF3 and Si02-NaF ( MYSEN and VIRGO, 1985b), they observed a band between 930 and 940 cm-', which they attributed to Si-F stretching vibrations.…”

Section: Discussionsupporting

confidence: 61%

“…In their study of Fin aluminosilicate glasses, MYSEN and VIRGO ( 1985a) suggested the presence of complexes of F with Na and Al in their samples. However, with the possible exception of one weak band component observed in the most F-rich compositions studied, they could not find any direct evidence for these species because of their low scattering intensity.…”

Section: Discussionmentioning

confidence: 99%

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Fluorine in silicate glasses: A multinuclear nuclear magnetic resonance study

Schaller

Dingwell

Keppler

et al. 1992

Geochimica et Cosmochimica Acta

149

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Abstract-Anhydrous nepheline, jadeite, and albite glasses doped with F as well as hydrous F-containing haplogranitic glasses were investigated using "F combined rotation and multiple-pulse spectroscopy; 19F + 29Si cross-polarization/magic angle spinning (MAS); and high-power r9F decoupled 29Si, 23Na, and 27A1 MAS nuclear magnetic resonance methods. Fluorine preferentially coordinates with Al to form octahedral AIF:-complexes in all glasses studied. In addition, F anions bridging two Al cations, units containing octahedral Al coordinated by both 0 and F, or tetrahedral Al-F complexes might be present. The presence of Si-F bonds cannot be entirely ruled out but appears unlikely on the basis of the 19F + 29Si CP/MAS spectra. There is no evidence for any significant coordination of F with alkalis in the glasses studied. 23Na spectra are identical for the samples and their F-free equivalents and the spectra do not change upon decoupling of 19F. The speciation of F in the hydrous and anhydrous glasses appears to be very similar. Over the range of F contents studied (up to 5 wt.%), there seems to be hardly any dependence of F speciation on the concentration of F in the samples. The spectroscopic results explain the decrease of the viscosity of silicate melts with increasing F content by removal of Al from bridging AlO,-units due to complexing with F, which causes depolymerization of the melt. The same mechanism can account for the shift of the eutectic point in the haplogranite system to more feldspar-rich compositions with increasing F content, and for the peraluminous composition of most F-rich granites. Liquid immiscibility in F-rich granitic melts might be caused by formation of (Na,K),AlF, units in the melt with little or no interaction with the silicate component.The presence of F in granitic melts might increase the solubility of high field strength cations by making nonbridging 0 atoms available which form complexes with these cations. INTRODLJCPIONFLUORINE IS ONE OF THE MOST important volatile components of natural magmas, both in mantle-derived melts (e.g., lamproites) and in highly fractionated granitic magmas. Concentrations of several wt.% are reported in high-fluorine rhyolites (CONGDON and NASH, 1988) and in ongonites ( KOVALENKO, 1973). Similar to water, the presence of F strongly reduces the viscosity of silicate melts ( DINGWELL et al., 1985;DINGWELL, 1989) and increases diffusion coefficients ( DINGWELL, 1985). Even small amounts of F in the order of 1 wt.% will therefore significantly change the transport properties, mobility, and eruption behavior of such magmas. The correlation between high concentrations of certain trace elements (Sn, Zr, Nb, Ta, U, Th, etc.) and high F contents in granites and granitic pegmatites (STEMPROK, 1982) has stimulated the investigation of phase equilibria in F-containing granitic systems. MANNING ( 198 1) has shown that F strongly lowers both solidus and liquidus temperatures in the haplogranite system and causes a shift of the eutectic point towards more feldspar-rich...

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Section: Discussionsupporting

confidence: 91%

Section: Discussionsupporting

confidence: 61%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Fluorine in silicate glasses: A multinuclear nuclear magnetic resonance study

Schaller

Dingwell

Keppler

et al. 1992

Geochimica et Cosmochimica Acta

149

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“…The addition of F into the melt promotes the formation of [SiO 3 F] 3-complexes of HREE and HFSE, resulting in depolymerization and reduction in the availability of SiO 4 tetrahedra to form HREE-and HFSE-bearing phases (Dingwell 1988). The development of F-bearing fluids and their interaction with the silicic melt at the late magmatic stage enhance element fractionation, since the addition of fluorine decreases silicate melt viscosity (Mysen and Virgo 1985) and expands the primary phase field of quartz (Manning 1981;Manning and Pichavant 1983), thus extending the duration of crystallization. However, the altered granite bodies contain extraordinarily high concentrations of HFSE that igneous processes alone seem insufficient to account for.…”

Section: Origin Of Rare-metal Mineralizationmentioning

confidence: 99%

Origin and hydrothermal alteration of rare-metal granites in the Al-Hamra area, northeastern Arabian Shield, Saudi Arabia

Qadhi

2007

Central European Geology

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The Jabal Hamra (538 Ma) and Jabal Abu ad Dud plutons in northeast Saudi Arabia are epizonal bodies consisting of alkali feldspar granite and alkali feldspar syenite. Fracture-controlled zones of highly altered granites are recorded along the margins of the plutons. The granites intrude metamorphosed volcano-sedimentary successions of the Matran Formation. The rocks of the two plutons are chemically indistinguishable. They are characterized by above-average Th, Nb, Y, Ta, Hf and Zr, very low CaO, TiO 2 , MgO, FeO and MnO, and by high contents of rare earth elements (REE). Tectonic discrimination diagrams suggest an intra-plate environment, with many geochemical and mineralogical features resembling post-orogenic A-type granites. Numerous local and regional geologic constraints indicate that the plutons were intruded in an extension-related setting following the cessation of Neoproterozoic arc-related magmatism. Geochemical data are consistent with their derivation by partial melting of depleted crust followed by fractional crystallization of feldspars, ferromagnesian minerals and REE-rich accessory phases. The radiogenic isotope data [eNd (T) values are +3.5 to +4.2] indicate that the granite magma was generated from a 'juvenile' source, which is typical of the rocks making up most of the Arabian-Nubian Shield. Rare-metal mineralization is associated with the fracture-controlled alteration zones that occur at Jabal Al Hamra and Jabal Abu ad Dud. The altered rocks are characterized by higher TiO 2 , Fe 2 O 3 , SiO 2 and lower Al 2 O 3 , CaO, Na 2 O, than the unaltered rocks. They show high and wide range in the total REE contents (804-15579 ppm), , Nb (51-3483 ppm), Hf (13-368 ppm), Zr (394-14887 ppm), Th (16-572 ppm) and U (4-143 ppm). Field observations and further petrographic and chemical studies suggest that the altered rocks and the rare metal enrichment are the products of hydrothermal-metasomatic alteration of the quartz alkali feldspar syenite and the alkali feldspar granite. The rare-metal enrichment was explained by orthomagmatic fluid transport of these elements as fluoride complexes, and their subsequent deposition as a result of mixing with externally derived Fe-rich fluids.

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“…Based on studies of alkaline and earth-alkaline aluminosilicate glasses, 7,22 in glasses without non-bridging oxygens the high-frequency region consists a combination of up to four main types of symmetric vibrations, defined by the number of neighbouring [AlO 4 ] À tetrahedra connected to one SiO 4 tetrahedron. 7 Following the well established terminology for structural types in pure silicate glasses, the corresponding species can be denoted Q n (xAl) where n characterizes the number of bridging oxygen and x the number of Al in the neighbouring tetrahedra. 23 In Li-containing Al-Si-O glasses the peak at B950 cm À1 represents the structural unit where one Si-O tetrahedron is connected with three neighbouring Al 3+ via oxygen bridges, (SiO)-Si(OAl) 3 , or (Q 4 (3Al)).…”

Section: Raman Spectroscopymentioning

confidence: 99%

Lithium conductivity in glasses of the Li₂O–Al₂O₃–SiO₂system

Ross

Welsch

Behrens

2015

Phys. Chem. Chem. Phys.

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To improve the understanding of Li-dynamics in oxide glasses, i.e. the effect of [AlO 4 ] À tetrahedra and non-bridging oxygens on the potential landscape, electrical conductivity of seven fully polymerized and partly depolymerized lithium aluminosilicate glasses was investigated using impedance spectroscopy (IS).Lithium is the only mobile particle in these materials. Data derived from IS, i.e. activation energies, preexponential factors and diffusivities for lithium, are interpreted in light of Raman spectroscopic analyses of local structures in order to identify building units, which are crucial for lithium dynamics and migration. In polymerized glasses (compositional join LiAlSiO 4 -LiAlSi 4 O 10 ) the direct current (DC) electrical conductivity continuously increases with increasing lithium content while lithium diffusivity is not affected by the Al/Si ratio in the glasses. Hence, the increase in electrical conductivity can be solely assigned to lithium concentration in the glasses. An excess of Li with respect to Al, i.e. the introduction of non-bridging oxygen into the network, causes a decrease in lithium mobility in the glasses. Activation energies in polymerized glasses (66 to 70 kJ mol À1 ) are significantly lower than those in depolymerized networks (76 to 78 kJ mol À1 ) while pre-exponential factors are nearly constant across all compositions. Comparison of the data with results for lithium silicates from the literature indicates a minimum in lithium diffusivity for glasses containing both aluminium tetrahedra and non-bridging oxygens. The findings allow a prediction of DC conductivity for a large variety of lithium aluminosilicate glass compositions.

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Structure and properties of fluorine-bearing aluminosilicate melts: the system Na2O-Al2O3-SiO2-F at 1 atm

Cited by 144 publications

References 34 publications

Fluorine in silicate glasses: A multinuclear nuclear magnetic resonance study

Fluorine in silicate glasses: A multinuclear nuclear magnetic resonance study

Origin and hydrothermal alteration of rare-metal granites in the Al-Hamra area, northeastern Arabian Shield, Saudi Arabia

Lithium conductivity in glasses of the Li₂O–Al₂O₃–SiO₂system

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Structure and properties of fluorine-bearing aluminosilicate melts: the system Na2O-Al2O3-SiO2-F at 1 atm

Cited by 144 publications

References 34 publications

Fluorine in silicate glasses: A multinuclear nuclear magnetic resonance study

Fluorine in silicate glasses: A multinuclear nuclear magnetic resonance study

Origin and hydrothermal alteration of rare-metal granites in the Al-Hamra area, northeastern Arabian Shield, Saudi Arabia

Lithium conductivity in glasses of the Li2O–Al2O3–SiO2system

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Lithium conductivity in glasses of the Li₂O–Al₂O₃–SiO₂system