Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10121325 | Physics of the Earth and Planetary Interiors | 2005 | 8 Pages |
Abstract
In situ X-ray diffraction measurements on a calcium aluminosilicate (CAS) phase have been carried out using a laser-heated diamond anvil cell up to a pressure of 44 GPa, employing a synchrotron radiation source. CAS is the major mineral formed from sediments subducted into the Earth's mantle. The sample was heated using a YAG laser after each pressure increment to relax the deviatoric stress in the sample. X-ray diffraction measurements were carried out at T = 300 K using an angle-dispersive technique. The pressure was calculated using an internal platinum metal pressure calibrant. The Birch-Murnaghan equation of state for the CAS phase obtained from the experimental unit cell parameters showed a density of Ï0 = 3.888 g/cm3 and a bulk modulus of K0 = 229 ± 9 GPa for Kâ²0 = 4.7 ± 0.7. When the first pressure derivative of the bulk modulus was fixed at Kâ²0 = 4, then the value of K0 = 239 ± 2 GPa. From the experimental compressibility, the density of the CAS phase was observed to be lower than the density of co-existing Al-bearing stishovite, calcium perovskite, calcium ferrite-type phases, and (Fe,Al)-bearing Mg-perovskite in subducted sediments in the lower mantle. Therefore, the density of subducted sediments in the lower mantle decreases with increasing mineral proportion of the CAS phase.
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Geophysics
Authors
Shigeaki Ono, Tsuyoshi Iizuka, Takumi Kikegawa,