کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4742340 1641564 2009 8 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Constraints on the Fe–S melt connectivity in mantle silicates from electrical impedance measurements
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات فیزیک زمین (ژئو فیزیک)
پیش نمایش صفحه اول مقاله
Constraints on the Fe–S melt connectivity in mantle silicates from electrical impedance measurements
چکیده انگلیسی

The connectivity of FeS melts in olivine and in a fertile peridotite matrix has been addressed through in situ electric impedance spectroscopy (IS) measurements at 1 GPa. A first series of experiments used sintered powder samples of a fertile peridotite xenolith mixed with 5–15 vol.% Fe70S30 of eutectic composition. The sheared high-T garnet peridotite with Mg# ∼ 0.90 is composed of 60 vol.% olivine, 15% orthopyroxene, 5.3% clinopyroxene and 19% garnet, the powder grain size was 20–30 μm, similar to the one employed by Yoshino et al. (2003). For a second series, San Carlos olivine aggregates were used as solid matrix and 10–20 vol.% of eutectic Fe70S30 were added. For these, the average grain size was 3 μm, much smaller than in the experiments by Yoshino et al. (2003). The powder mixtures of peridotite + Fe70S30 and olivine aggregates + Fe70S30 were first annealed for 2–5 days in a conventional piston cylinder at 1 GPa and 950–970 °C. The electrical conductivity of samples has been measured using the impedance spectroscopy method in a BN–graphite–CaF2 pressure cell with concentric cylindrical electrodes made from Mo- or Re-foil (the estimated oxygen fugacity was close to the IW-buffer). The results indicate that up to 15 vol.% of Fe70S30 the melt phase does not built a stable interconnected network in a peridotite matrix, as was recently indicated by Walte et al. (2007). The percolation threshold for a stable FeS network in olivine matrix lies at 17.5 vol.%, much higher the 6 vol.% found by Yoshino et al. (2003). Our result is in line with the high dihedral angles of typically 70–100° for Fe–S melts in mantle materials. The higher interconnectivity threshold of this study, as compared to previous studies (Yoshino et al., 2003, 2004; Roberts et al., 2007) is a result of our smaller starting grain sizes (for olivine) in combination with much longer run durations. Both these experimental conditions result in enhanced grain growth and thus to a higher degree of textural equilibration, leading to the occurrence of the time depending pinging off of Fe–S melt films in our texturally more mature experiments.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Physics of the Earth and Planetary Interiors - Volume 177, Issues 3–4, December 2009, Pages 139–146
نویسندگان
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