Structural environments of incompatible elements in silicate glass/melt systems: 1. Zirconium at trace levels

Journal Article · Sat Jun 01 04:00:00 EDT 1991 · Geochimica et Cosmochimica Acta; (United States)

OSTI ID:6140155

Ponader, C W; Brown, Jr, G E ^[1]; Farges, F

---

1. Stanford Univ., CA (United States)

The structural environments of trace levels ({approx}2,000 ppm) of Zr{sup 4+} in several silicate glasses were examined as a function of melt composition and polymerization using Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. Glass compositions investigated were albite (NaAlSi{sub 3}O{sub 8}: AB) and a peralkaline composition (Na{sub 3.3}AlSi{sub 7}O{sub 17}: PR). Zirconium was added to the oxide-carbonate mix prior to melting in the form of ZrO{sub 2} (baddeleyite). A second set of Zr-silicate glasses containing 2,000 ppm Zr and 1.0 to 2.4 wt% halogens (F as NaF and Cl as NaCl) was also synthesized. These included the Zr-AB and Zr-PR base-glass compositions as well as Zr-sodium trisilicate composition (Na{sub 2}Si{sub 3}O{sub 7}: TS). In all glasses studied, Zr is mainly 6-coordinated by oxygen atoms. In the most polymerized glass (AB), a small but significant amount of Zr was also found to occur in 8-coordinated sites (d(Zr-O) {approximately} 2.22 {angstrom}). No clear evidence for F or Cl complexes of Zr was observed in any of the halogen-containing glasses. The local environment around Zr is more strongly influenced by bonding requirements than by the network topology of the melt. Stabilization of zirconium in 6-coordinated sites in relatively depolymerized melts should act to decrease the crystal-melt partition coefficients of Zr and may explain the normally incompatible character of Zr during magmatic differentiation. The presence of Zr in sites of higher coordination (ZrO{sub 8}) in highly polymerized melts could be a precursor to the crystallization of zircon from such melts and thus may explain why Zr becomes a more compatible element, especially in the latest stages of magmatic differentiation.

• OSTI ID: 6140155
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Journal Name: Geochimica et Cosmochimica Acta; (United States) Vol. 55:6; ISSN GCACA; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
ALBITE
CHALCOGENIDES
CHARGED PARTICLES
CHEMICAL COMPOSITION
CHEMICAL REACTIONS
CHEMISTRY
COMPLEXES
ELEMENTS
FELDSPARS
GEOCHEMISTRY
IGNEOUS ROCKS
IONS
MAGMA
METALS
MINERALS
MOLECULAR STRUCTURE
OXIDES
OXYGEN COMPOUNDS
PETROCHEMISTRY
POLYMERIZATION
ROCKS
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
SPECTROSCOPY
STRUCTURAL CHEMICAL ANALYSIS
TRANSITION ELEMENT COMPLEXES
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
X-RAY SPECTROSCOPY
ZIRCONIUM
ZIRCONIUM COMPLEXES
ZIRCONIUM COMPOUNDS
ZIRCONIUM IONS
ZIRCONIUM OXIDES
ZIRCONIUM SILICATES