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A new hydrous silicate, a water reservoir, in the upper part of the lower mantle
Author(s) -
Ohtani Eiji,
Mizobata Hiroki,
Kudoh Yasuhiro,
Nagase Toshiro,
Arashi Haruo,
Yurimoto Hisayoshi,
Miyagi Isoji
Publication year - 1997
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/97gl00874
Subject(s) - silicate , periclase , mantle (geology) , geology , mineralogy , formula unit , phase (matter) , stishovite , analytical chemistry (journal) , chemical composition , geochemistry , chemistry , crystallography , quartz , crystal structure , environmental chemistry , paleontology , organic chemistry , spinel
We synthesized a new hydrous silicate in the pressure range from 20 GPa to 24 GPa at 800–1300°C. This phase, named tentatively as phase G, has a hexagonal unit cell, a=4.790 (3) Å and c=4.344 (3) Å, and V=86.3 (2) ų and the atomic ratio Mg/Si=0.66±0.03. SIMS analysis revealed that it contains 14.5±2.0wt% water. Phase G has a chemical formula of Mg 1.14 Si 1.73 H 2.81 O 6 and a density of 3.37g/cm³. Phase G coexists with periclase and Mg‐perovskite under the lower mantle conditions, and thus it can be a reservoir of water in cold slabs penetrating into the lower mantle.