Limits...
Experimental chlorine partitioning between forsterite, enstatite and aqueous fluid at upper mantle conditions.

Fabbrizio A, Stalder R, Hametner K, Günther D - Geochim. Cosmochim. Acta (2013)

Bottom Line: Applying the new mineral/fluid partition coefficients to fluids in subduction zones, a contribution between 0.15% and 20% of the total chlorine from the nominally anhydrous minerals is estimated.Infrared spectra of experimental forsterite show absorption bands at 3525 and 3572 cm(-1) that are characteristic for hydroxyl point defects associated with trace Ti substitutions, and strongly suggest that the TiO2 content of the system can influence the chlorine and OH incorporation via the stabilization of Ti-clinohumite-like point defects.The water contents for coexisting forsterite and enstatite in some runs were determined using unpolarized IR spectra and calculated water partition coefficients [Formula: see text] are between 0.01 and 0.5.

View Article: PubMed Central - PubMed

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

ABSTRACT

Cl partition coefficients between forsterite, enstatite and coexisting Cl-bearing aqueous fluids were determined in a series of high pressure and temperature piston cylinder experiments at 2 GPa between 900 and 1300 °C in the system MgO-SiO2-H2O-NaCl-BaO-C±CaCl2±TiO2±Al2O3±F. 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 content of forsterite and enstatite was measured by electron microprobe, and the nature of hydrous defects was investigated by infrared spectroscopy. Partition coefficients show similar incompatibility for Cl in forsterite and enstatite, with D Cl (fo/fl) = 0.0012 ± 0.0006, D Cl (en/fl) = 0.0018 ± 0.0008 and D Cl (fo/en) = 1.43 ± 0.71. The values determined for mineral/fluid partitioning are very similar to previously determined values for mineral/melt. Applying the new mineral/fluid partition coefficients to fluids in subduction zones, a contribution between 0.15% and 20% of the total chlorine from the nominally anhydrous minerals is estimated. Infrared spectra of experimental forsterite show absorption bands at 3525 and 3572 cm(-1) that are characteristic for hydroxyl point defects associated with trace Ti substitutions, and strongly suggest that the TiO2 content of the system can influence the chlorine and OH incorporation via the stabilization of Ti-clinohumite-like point defects. The water contents for coexisting forsterite and enstatite in some runs were determined using unpolarized IR spectra and calculated water partition coefficients [Formula: see text] are between 0.01 and 0.5.

No MeSH data available.


Unpolarized IR spectra of forsterite averaged over 10–15 randomly oriented crystals for each run (a = run Cl-5, b = Cl-7, c = Cl-19, d = Cl-20, e = Cl-21, f = Cl-9). Experimental temperatures and amount of Ti (ppm) in forsterite are reported above each spectra. Spectra are normalized to 1 cm thickness. Vertical dashed lines indicate the positions of OH bands. B.d.l. = below detection limit. No Ti means Ti-free experiment.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4375631&req=5

f0040: Unpolarized IR spectra of forsterite averaged over 10–15 randomly oriented crystals for each run (a = run Cl-5, b = Cl-7, c = Cl-19, d = Cl-20, e = Cl-21, f = Cl-9). Experimental temperatures and amount of Ti (ppm) in forsterite are reported above each spectra. Spectra are normalized to 1 cm thickness. Vertical dashed lines indicate the positions of OH bands. B.d.l. = below detection limit. No Ti means Ti-free experiment.

Mentions: Ti-bearing forsterite crystals (Table 3 and Fig. 8) exhibit intense absorption bands at 3525 and 3572 cm−1. Minor absorption bands are observed at 3612 cm−1 and at 3325 and 3352 cm−1. Ti-free forsterite displays also the absorption band at 3612 cm−1, but the band at 3572 cm−1 tends to disappear and is substituted by two weak peaks at ∼3568 and ∼3580 cm−1. The thickness and the average orientation of the samples are comparable and hence the intensity of absorption is related to the amount of OH. The observed spectra indicate that Ti-bearing forsterite incorporates significantly higher amounts of OH compared to Ti-free forsterite. Furthermore, Ti-forsterite from the runs at 900 and 1100 °C exhibits stronger OH-bands than the Ti-forsterite derived from the run at 1300 °C.


Experimental chlorine partitioning between forsterite, enstatite and aqueous fluid at upper mantle conditions.

Fabbrizio A, Stalder R, Hametner K, Günther D - Geochim. Cosmochim. Acta (2013)

Unpolarized IR spectra of forsterite averaged over 10–15 randomly oriented crystals for each run (a = run Cl-5, b = Cl-7, c = Cl-19, d = Cl-20, e = Cl-21, f = Cl-9). Experimental temperatures and amount of Ti (ppm) in forsterite are reported above each spectra. Spectra are normalized to 1 cm thickness. Vertical dashed lines indicate the positions of OH bands. B.d.l. = below detection limit. No Ti means Ti-free experiment.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4375631&req=5

f0040: Unpolarized IR spectra of forsterite averaged over 10–15 randomly oriented crystals for each run (a = run Cl-5, b = Cl-7, c = Cl-19, d = Cl-20, e = Cl-21, f = Cl-9). Experimental temperatures and amount of Ti (ppm) in forsterite are reported above each spectra. Spectra are normalized to 1 cm thickness. Vertical dashed lines indicate the positions of OH bands. B.d.l. = below detection limit. No Ti means Ti-free experiment.
Mentions: Ti-bearing forsterite crystals (Table 3 and Fig. 8) exhibit intense absorption bands at 3525 and 3572 cm−1. Minor absorption bands are observed at 3612 cm−1 and at 3325 and 3352 cm−1. Ti-free forsterite displays also the absorption band at 3612 cm−1, but the band at 3572 cm−1 tends to disappear and is substituted by two weak peaks at ∼3568 and ∼3580 cm−1. The thickness and the average orientation of the samples are comparable and hence the intensity of absorption is related to the amount of OH. The observed spectra indicate that Ti-bearing forsterite incorporates significantly higher amounts of OH compared to Ti-free forsterite. Furthermore, Ti-forsterite from the runs at 900 and 1100 °C exhibits stronger OH-bands than the Ti-forsterite derived from the run at 1300 °C.

Bottom Line: Applying the new mineral/fluid partition coefficients to fluids in subduction zones, a contribution between 0.15% and 20% of the total chlorine from the nominally anhydrous minerals is estimated.Infrared spectra of experimental forsterite show absorption bands at 3525 and 3572 cm(-1) that are characteristic for hydroxyl point defects associated with trace Ti substitutions, and strongly suggest that the TiO2 content of the system can influence the chlorine and OH incorporation via the stabilization of Ti-clinohumite-like point defects.The water contents for coexisting forsterite and enstatite in some runs were determined using unpolarized IR spectra and calculated water partition coefficients [Formula: see text] are between 0.01 and 0.5.

View Article: PubMed Central - PubMed

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

ABSTRACT

Cl partition coefficients between forsterite, enstatite and coexisting Cl-bearing aqueous fluids were determined in a series of high pressure and temperature piston cylinder experiments at 2 GPa between 900 and 1300 °C in the system MgO-SiO2-H2O-NaCl-BaO-C±CaCl2±TiO2±Al2O3±F. 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 content of forsterite and enstatite was measured by electron microprobe, and the nature of hydrous defects was investigated by infrared spectroscopy. Partition coefficients show similar incompatibility for Cl in forsterite and enstatite, with D Cl (fo/fl) = 0.0012 ± 0.0006, D Cl (en/fl) = 0.0018 ± 0.0008 and D Cl (fo/en) = 1.43 ± 0.71. The values determined for mineral/fluid partitioning are very similar to previously determined values for mineral/melt. Applying the new mineral/fluid partition coefficients to fluids in subduction zones, a contribution between 0.15% and 20% of the total chlorine from the nominally anhydrous minerals is estimated. Infrared spectra of experimental forsterite show absorption bands at 3525 and 3572 cm(-1) that are characteristic for hydroxyl point defects associated with trace Ti substitutions, and strongly suggest that the TiO2 content of the system can influence the chlorine and OH incorporation via the stabilization of Ti-clinohumite-like point defects. The water contents for coexisting forsterite and enstatite in some runs were determined using unpolarized IR spectra and calculated water partition coefficients [Formula: see text] are between 0.01 and 0.5.

No MeSH data available.