کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
8915757 | 1641466 | 2018 | 49 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Phase relations and mineral chemistry in pyrolitic mantle at 1600-2200â¯Â°C under pressures up to the uppermost lower mantle: Phase transitions around the 660-km discontinuity and dynamics of upwelling hot plumes
دانلود مقاله + سفارش ترجمه
دانلود مقاله ISI انگلیسی
رایگان برای ایرانیان
موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
فیزیک زمین (ژئو فیزیک)
پیش نمایش صفحه اول مقاله
![عکس صفحه اول مقاله: Phase relations and mineral chemistry in pyrolitic mantle at 1600-2200â¯Â°C under pressures up to the uppermost lower mantle: Phase transitions around the 660-km discontinuity and dynamics of upwelling hot plumes Phase relations and mineral chemistry in pyrolitic mantle at 1600-2200â¯Â°C under pressures up to the uppermost lower mantle: Phase transitions around the 660-km discontinuity and dynamics of upwelling hot plumes](/preview/png/8915757.png)
چکیده انگلیسی
We determined phase relations of pyrolite at 12-28â¯GPa and 1600-2200â¯Â°C using a 6-8â¯Kawai-type multianvil apparatus. A large number of high pressure and high temperature experiments were conducted to constrain the phase relations especially around 660-km depth, compared with previous studies. The phase relations drastically change between 19 and 23â¯GPa with temperature as follows. At 19-22â¯GPa, a phase transition of ringwoodite (Rw) to garnet (Gt)â¯+â¯magnesiowüstite (Mw) occurs at 1800â¯Â°C, and no Rw is observed at 2200â¯Â°C. The mineral proportion of Gt increases with increasing temperature due to this decomposition reaction and becomes larger than that of Rw above 1800â¯Â°C. At 23â¯GPa, pyrolite crystallizes to a mineral assemblage of bridgmanite (Bm)â¯+â¯Mwâ¯+â¯Gtâ¯+â¯calcium perovskite by the post-spinel (pSp) transition at 1600-2000â¯Â°C and the post-garnet (pGt) transition at 2100-2200â¯Â°C, the latter of which is defined as a phase transition of a part of Gt to Bm. Clapeyron slopes of the pSp transition and the pGt transition are determined to be â1 and 5â¯MPa/°C, respectively, in this study. Gt is stable at any temperatures around the 660-km discontinuity (D660), and Gt-disappearance reaction occurs at 25â¯GPa with no temperature dependence. Densities of pyrolite were calculated in various pressure and temperature conditions by using the mineral proportions and available data of equations of state. The density at 1600â¯Â°C is higher than that at 1800-2200â¯Â°C at any pressure-temperature conditions in this study. In particular, the drastic density drop occurs at 19-24â¯GPa between 1600 and 1800-2200â¯Â°C because of increase of Gt proportion with increasing temperature. These suggest that upwelling hot plumes composed of pyrolite from the lower mantle do not stagnate and their ascent is promoted across D660. The mineral proportions and the density changes also suggest that the phase transition which causes D660 changes around 1800â¯Â°C from the pSp to the pGt transitions because of the mineral proportion inversion between Rw and Gt.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Physics of the Earth and Planetary Interiors - Volume 274, January 2018, Pages 127-137
Journal: Physics of the Earth and Planetary Interiors - Volume 274, January 2018, Pages 127-137
نویسندگان
Takayuki Ishii, Hiroshi Kojitani, Masaki Akaogi,