Research output: Contribution to journal › Article › peer-review
High-pressure phase transitions of anorthosite crust in the Earth's deep mantle. / Nishi, Masayuki; Gréaux, Steeve; Tateno, Shigehiko et al.
In: Geoscience Frontiers, Vol. 9, No. 6, 01.11.2018, p. 1859-1870.Research output: Contribution to journal › Article › peer-review
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TY - JOUR
T1 - High-pressure phase transitions of anorthosite crust in the Earth's deep mantle
AU - Nishi, Masayuki
AU - Gréaux, Steeve
AU - Tateno, Shigehiko
AU - Kuwayama, Yasuhiro
AU - Kawai, Kenji
AU - Irifune, Tetsuo
AU - Maruyama, Shigenori
PY - 2018/11/1
Y1 - 2018/11/1
N2 - We investigated phase relations, mineral chemistry, and density of lunar highland anorthosite at conditions up to 125 GPa and 2000 K. We used a multi-anvil apparatus and a laser-heated diamond-anvil cell for this purpose. In-situ X-ray diffraction measurements at high pressures and composition analysis of recovered samples using an analytical transmission electron microscope showed that anorthosite consists of garnet, CaAl4Si2O11-rich phase (CAS phase), and SiO2 phases in the upper mantle and the mantle transition zone. Under lower mantle conditions, these minerals transform to the assemblage of bridgmanite, Ca-perovskite, corundum, stishovite, and calcium ferrite-type aluminous phase through the decomposition of garnet and CAS phase at around 700 km depth. Anorthosite has a higher density than PREM and pyrolite in the upper mantle, while its density becomes comparable or lower under lower mantle conditions. Our results suggest that ancient anorthosite crust subducted down to the deep mantle was likely to have accumulated at 660-720 km depth without coming back to the Earth's surface. Some portions of the anorthosite crust might have circulated continuously in the Earth's deep interior by mantle convection and potentially subducted to the bottom of the lower mantle when carried within layers of dense basaltic rocks.
AB - We investigated phase relations, mineral chemistry, and density of lunar highland anorthosite at conditions up to 125 GPa and 2000 K. We used a multi-anvil apparatus and a laser-heated diamond-anvil cell for this purpose. In-situ X-ray diffraction measurements at high pressures and composition analysis of recovered samples using an analytical transmission electron microscope showed that anorthosite consists of garnet, CaAl4Si2O11-rich phase (CAS phase), and SiO2 phases in the upper mantle and the mantle transition zone. Under lower mantle conditions, these minerals transform to the assemblage of bridgmanite, Ca-perovskite, corundum, stishovite, and calcium ferrite-type aluminous phase through the decomposition of garnet and CAS phase at around 700 km depth. Anorthosite has a higher density than PREM and pyrolite in the upper mantle, while its density becomes comparable or lower under lower mantle conditions. Our results suggest that ancient anorthosite crust subducted down to the deep mantle was likely to have accumulated at 660-720 km depth without coming back to the Earth's surface. Some portions of the anorthosite crust might have circulated continuously in the Earth's deep interior by mantle convection and potentially subducted to the bottom of the lower mantle when carried within layers of dense basaltic rocks.
KW - Anorthosite
KW - Diamond-anvil cell
KW - Mantle dynamics
KW - Multi-anvil apparatus
KW - Phase transformation
KW - SYSTEM
KW - HIGH-TEMPERATURE
KW - GARNET
KW - SUBDUCTION
KW - X-RAY-DIFFRACTION
KW - THERMAL EQUATION
KW - CONTINENTAL-CRUST
KW - EQUATION-OF-STATE
KW - SOLID-SOLUTION
KW - GPA
UR - http://www.scopus.com/inward/record.url?scp=85035100506&partnerID=8YFLogxK
U2 - 10.1016/j.gsf.2017.10.002
DO - 10.1016/j.gsf.2017.10.002
M3 - Article
AN - SCOPUS:85035100506
VL - 9
SP - 1859
EP - 1870
JO - Geoscience Frontiers
JF - Geoscience Frontiers
SN - 1674-9871
IS - 6
ER -
ID: 9673110