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MgSiO3-FeSiO3-Al2O3 in the Earth's lower mantle: Perovskite and garnet at 1200 km depthNatural pyroxene and garnet starting material are used to study the effects of joint Fe and Al substitution into MgSiO3 perovskite at approxmiately 50 GPa. Garnet is found to coexist with perovskite in samples containing both Fe and Al to pressures occurring deep into the lower mantel (approximately 1200 km depth). The volume of the perovskite unit cell is V(sub o(Angstrom(exp 3)) = 162.59 + 5.95x(sub FeSiO3) + 10.80x(sub Al2O3) with aluminum causing a significant increase in the distortion from the ideal cubic cell. On the basis of a proposed extension of the MgSiO3-Al2O3 high-pressure phase diagram toward FeSiO3, Fe is shown to partition preferentially into the garnet phase. The stability of garnet deep into the lower mantel may hinder the penetration of subducted slabs below the transition zone.
Document ID
19950054972
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
O'Neill, Bridget
(Univ. of California, Berkerley, CA United States)
Jeanloz, Raymond
(Univ. of California, Berkerley, CA United States)
Date Acquired
August 16, 2013
Publication Date
October 10, 1994
Publication Information
Publication: Journal of Geophysical Research
Volume: 99
Issue: B10
ISSN: 0148-0227
Subject Category
Geophysics
Accession Number
95A86571
Funding Number(s)
CONTRACT_GRANT: NSF EAR-89-0301
CONTRACT_GRANT: NAGW-604
Distribution Limits
Public
Copyright
Other

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