کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4741720 1641522 2013 10 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Ringwoodite growth rates from olivine with ∼75 ppmw H2O: Metastable olivine must be nearly anhydrous to exist in the mantle transition zone
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات فیزیک زمین (ژئو فیزیک)
پیش نمایش صفحه اول مقاله
Ringwoodite growth rates from olivine with ∼75 ppmw H2O: Metastable olivine must be nearly anhydrous to exist in the mantle transition zone
چکیده انگلیسی
It has been previously demonstrated that as little as 300 ppmw H2O increases wadsleyite and ringwoodite growth rates to magnitudes that are inconsistent with the metastable olivine hypothesis. To further test this hypothesis, we present new ringwoodite growth rate measurements from olivine with ∼75 ppmw H2O at 18 GPa and 700, 900, and 1100 °C. These growth rates are nearly identical to those from olivine with ∼300 ppmw H2O, and significantly higher than those from nominally anhydrous olivine. We infer that transformation of olivine with 75-300 ppmw H2O is primarily enhanced by hydrolytic weakening of reaction rims, which reduces the elastic strain-energy barrier to growth. We present a new method for fitting non-linear nominally anhydrous data, to demonstrate that reduction of growth rates by elastic strain energy is an additional requirement for metastable olivine. Based on previous thermokinetic modeling, these enhanced growth rates are inconsistent with the persistence of metastable olivine wedges into the mantle transition zone. Metastable persistence of olivine into the mantle transition-zone would therefore require <75 ppmw H2O.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Physics of the Earth and Planetary Interiors - Volume 219, June 2013, Pages 1-10
نویسندگان
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