Abstract
High-pressure and high-temperature phase transformations of Ca3Al2Si3O12 grossular garnet were examined at 19-26GPa and 700-2000K using Kawai-type multi-anvil apparatus coupled with in situ X-ray diffraction (XRD). Recovered samples were analyzed by a combination of micro-focused X-ray diffraction (μ-XRD) and transmission electron microscopy (TEM). The results show that grossular garnet gradually transforms to an Al-rich CaSiO3 perovskite at 22-26GPa and 1000-1400K. The transition boundary can be expressed as P (GPa)=-0.0082×T (K)+33.05. When the garnet completely disappears, we observed orthorhombic CaSiO3 perovskite with a grossular composition. At 20-24GPa and temperatures above 1500K the CAS phase with the composition CaAl4Si2O11 appears to accommodate excess Al from the perovskite along with two distinct populations of Al-bearing CaSiO3 perovskites, with Al content of 3.7 and 10.0wt% Al2O3, respectively. The pressure and temperature of these transitions correspond to the lowermost part of the transition zone and therefore it suggests that Ca-rich aluminosilicates could provide alternative candidates to explain multiple seismic reflections near the 660km depth discontinuity.
Original language | English |
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Pages (from-to) | 89-99 |
Number of pages | 11 |
Journal | Physics of the Earth and Planetary Interiors |
Volume | 185 |
Issue number | 3-4 |
DOIs | |
Publication status | Published - 2011 Apr |
Externally published | Yes |
Keywords
- Al-bearing CaSiO perovskite
- Experimental mineralogy
- Grossular garnet
- High-pressure
- High-temperature
- In situ X-ray diffraction
- Phase relation
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Geophysics
- Physics and Astronomy (miscellaneous)
- Space and Planetary Science