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Experimental partitioning of halogens and other trace elements between olivine, pyroxenes, amphibole and aqueous fluid at 2 GPa and 900-1,300 °C.

Fabbrizio A, Stalder R, Hametner K, Günther D, Marquardt K - Contrib Mineral Petrol (2013)

Bottom Line: Furthermore, partitioning results for incompatible trace element show that compatibilities of trace elements are generally ordered as D (amph/fluid) ≈ D (cpx/fluid) > D (opx/fluid) > D (ol/fluid) but that D (mineral/fluid) for Li and P is very similar for all observed silicate phases.In F ± TiO2-bearing systems, additional absorption bands appear at ~3,535, ~3,595, 3,640 and 3,670 cm(-1).Absorption bands at ~3,530 and ~3,570 cm(-1), previously assigned to humite-like point defects, profit from low synthesis temperatures and the presence of F.

View Article: PubMed Central - PubMed

Affiliation: Institute of Mineralogy and Petrography, University of Innsbruck, Innrain 52f, 6020 Innsbruck, Austria.

ABSTRACT

We present new partition coefficients for various trace elements including Cl between olivine, pyroxenes, amphibole and coexisting chlorine-bearing aqueous fluid in a series of high-pressure experiments at 2 GPa between 900 and 1,300 °C in natural and synthetic systems. Diamond aggregates were added to the experimental capsule set-up in order to separate the fluid from the solid residue and enable in situ analysis of the quenched solute by LA-ICP-MS. The chlorine and fluorine contents in mantle minerals were measured by electron microprobe, and the nature of OH defects was investigated by infrared spectroscopy. Furthermore, a fluorine-rich olivine from one selected sample was investigated by TEM. Results reveal average Cl concentrations in olivine and pyroxenes around 20 ppm and up to 900 ppm F in olivine, making olivine an important repository of halogens in the mantle. Chlorine is always incompatible with Cl partition coefficients D Cl (olivine/fluid) varying between 10(-5) and 10(-3), whereas D Cl (orthopyroxene/fluid) and D Cl (clinopyroxene/fluid) are ~10(-4) and D Cl (amphibole/fluid) is ~5 × 10(-3). Furthermore, partitioning results for incompatible trace element show that compatibilities of trace elements are generally ordered as D (amph/fluid) ≈ D (cpx/fluid) > D (opx/fluid) > D (ol/fluid) but that D (mineral/fluid) for Li and P is very similar for all observed silicate phases. Infrared spectra of olivine synthesized in a F-free Ti-bearing system show absorption bands at 3,525 and ~3,570 cm(-1). In F ± TiO2-bearing systems, additional absorption bands appear at ~3,535, ~3,595, 3,640 and 3,670 cm(-1). Absorption bands at ~3,530 and ~3,570 cm(-1), previously assigned to humite-like point defects, profit from low synthesis temperatures and the presence of F. The presence of planar defects could not be proved by TEM investigations, but dislocations in the olivine lattice were observed and are suggested to be an important site for halogen incorporation in olivine.

No MeSH data available.


Related in: MedlinePlus

Polarized IR spectra of olivine sections parallel to α, β, γ and average spectrum (α + β+γ)/3. Unpolarized IR spectra of olivine averaged over 10–15 randomly oriented crystals from the MSH + F ± TiO2 system
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Fig2: Polarized IR spectra of olivine sections parallel to α, β, γ and average spectrum (α + β+γ)/3. Unpolarized IR spectra of olivine averaged over 10–15 randomly oriented crystals from the MSH + F ± TiO2 system

Mentions: All experimental charges were cut as whole capsule by a diamond wire saw to preserve the texture, and then, double-sided polished wafers of 150 μm thickness were prepared. Sample thicknesses were measured using a Mitutoyo micrometer and are accurate to ±2 μm. In order to evaluate the orientation of the measured olivine crystals, reference spectra on oriented olivine crystals from Stöppling/Germany (Oehm et al. 1983) were recorded that were later compared with the olivine spectra of the experimental charges (Fig. 2).Fig. 2


Experimental partitioning of halogens and other trace elements between olivine, pyroxenes, amphibole and aqueous fluid at 2 GPa and 900-1,300 °C.

Fabbrizio A, Stalder R, Hametner K, Günther D, Marquardt K - Contrib Mineral Petrol (2013)

Polarized IR spectra of olivine sections parallel to α, β, γ and average spectrum (α + β+γ)/3. Unpolarized IR spectra of olivine averaged over 10–15 randomly oriented crystals from the MSH + F ± TiO2 system
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4459431&req=5

Fig2: Polarized IR spectra of olivine sections parallel to α, β, γ and average spectrum (α + β+γ)/3. Unpolarized IR spectra of olivine averaged over 10–15 randomly oriented crystals from the MSH + F ± TiO2 system
Mentions: All experimental charges were cut as whole capsule by a diamond wire saw to preserve the texture, and then, double-sided polished wafers of 150 μm thickness were prepared. Sample thicknesses were measured using a Mitutoyo micrometer and are accurate to ±2 μm. In order to evaluate the orientation of the measured olivine crystals, reference spectra on oriented olivine crystals from Stöppling/Germany (Oehm et al. 1983) were recorded that were later compared with the olivine spectra of the experimental charges (Fig. 2).Fig. 2

Bottom Line: Furthermore, partitioning results for incompatible trace element show that compatibilities of trace elements are generally ordered as D (amph/fluid) ≈ D (cpx/fluid) > D (opx/fluid) > D (ol/fluid) but that D (mineral/fluid) for Li and P is very similar for all observed silicate phases.In F ± TiO2-bearing systems, additional absorption bands appear at ~3,535, ~3,595, 3,640 and 3,670 cm(-1).Absorption bands at ~3,530 and ~3,570 cm(-1), previously assigned to humite-like point defects, profit from low synthesis temperatures and the presence of F.

View Article: PubMed Central - PubMed

Affiliation: Institute of Mineralogy and Petrography, University of Innsbruck, Innrain 52f, 6020 Innsbruck, Austria.

ABSTRACT

We present new partition coefficients for various trace elements including Cl between olivine, pyroxenes, amphibole and coexisting chlorine-bearing aqueous fluid in a series of high-pressure experiments at 2 GPa between 900 and 1,300 °C in natural and synthetic systems. Diamond aggregates were added to the experimental capsule set-up in order to separate the fluid from the solid residue and enable in situ analysis of the quenched solute by LA-ICP-MS. The chlorine and fluorine contents in mantle minerals were measured by electron microprobe, and the nature of OH defects was investigated by infrared spectroscopy. Furthermore, a fluorine-rich olivine from one selected sample was investigated by TEM. Results reveal average Cl concentrations in olivine and pyroxenes around 20 ppm and up to 900 ppm F in olivine, making olivine an important repository of halogens in the mantle. Chlorine is always incompatible with Cl partition coefficients D Cl (olivine/fluid) varying between 10(-5) and 10(-3), whereas D Cl (orthopyroxene/fluid) and D Cl (clinopyroxene/fluid) are ~10(-4) and D Cl (amphibole/fluid) is ~5 × 10(-3). Furthermore, partitioning results for incompatible trace element show that compatibilities of trace elements are generally ordered as D (amph/fluid) ≈ D (cpx/fluid) > D (opx/fluid) > D (ol/fluid) but that D (mineral/fluid) for Li and P is very similar for all observed silicate phases. Infrared spectra of olivine synthesized in a F-free Ti-bearing system show absorption bands at 3,525 and ~3,570 cm(-1). In F ± TiO2-bearing systems, additional absorption bands appear at ~3,535, ~3,595, 3,640 and 3,670 cm(-1). Absorption bands at ~3,530 and ~3,570 cm(-1), previously assigned to humite-like point defects, profit from low synthesis temperatures and the presence of F. The presence of planar defects could not be proved by TEM investigations, but dislocations in the olivine lattice were observed and are suggested to be an important site for halogen incorporation in olivine.

No MeSH data available.


Related in: MedlinePlus