کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
8915762 | 1641466 | 2018 | 11 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
High-pressure phase relation of KREEP basalts: A clue for finding the lost Hadean crust?
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
فیزیک زمین (ژئو فیزیک)
پیش نمایش صفحه اول مقاله
چکیده انگلیسی
The phase relations, mineral chemistry and density of KREEP basalt were investigated at pressures of 12-125â¯GPa and temperatures up to 2810â¯K by a combination of large volume multi-anvil press experiments and in situ synchrotron X-ray diffraction measurements in a laser-heated diamond anvil cell. Our results showed that grossular-rich majorite garnet, liebermannite and Al-bearing stishovite are dominant in the upper-to-middle part of the upper mantle while in the lowermost transition zone a dense Ti-rich CaSiO3 perovskite exsoluted from the garnet, which becomes more pyropic with increasing pressure. At lower mantle conditions, these minerals transform into an assemblage of bridgmanite, Ca-perovskite, Al-stishovite, the new aluminium-rich (NAL) phase and the calcium-ferrite type (CF) phase. At pressures higher than 50â¯GPa, NAL phase completely dissolved into the CF phase, which becomes the main deposit of alkali metals in the lower mantle. The density of KREEP estimated from phase compositions obtained by energy dispersive X-ray spectroscopy (EDS) in scanning (SEM) and transmission (TEM) electron microscopes, was found substantially denser than pyrolite suggesting that the Earth primordial crust likely subducted deep into the Earth's mantle after or slightly before the final solidification of magma ocean at 4.53â¯Ga. Radiogenic elements U, Th and 40K which were abundant in the final residue of magma ocean were brought down along the subduction of the primordial crust and generate heat by decay after the settlement of the primordial crust on top of the CMB, suggesting the non-homogeneous distribution of radiogenic elements in the Hadean mantle with implications for the thermal history of the Earth.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Physics of the Earth and Planetary Interiors - Volume 274, January 2018, Pages 184-194
Journal: Physics of the Earth and Planetary Interiors - Volume 274, January 2018, Pages 184-194
نویسندگان
Steeve Gréaux, Masayuki Nishi, Shigehiko Tateno, Yasuhiro Kuwayama, Naohisa Hirao, Kenji Kawai, Shigenori Maruyama, Tetsuo Irifune,