Abstract
Infrared absorption spectra are presented for four hydrous magnesian silicates which are stable at high pressures and high temperatures characteristic of the earth's mantle: phase A (Mg7Si2O14H6), phase B (approx. Mg23Si8O42H6), chondrodite (Mg5Si2O10H2), clinohumite (Mg9Si4O18H2). The results show that phase B as well as phase A, chondrodite and clinohumite contain hydroxyl groups in their structures. It is also suggested that phase B, in addition to phase A, could be of potential importance in the upper mantle and transition zone as a dense host mineral for hydroxyl ions. Chemical composition of phase A was reexamined by microprobe analysis: it agrees well with Mg7Si2O14H6, estimated by Yamamoto and Akimoto (1974, 1977), but disagrees with a newly proposed formula Mg2SiO5H2 by Benimoff and Sclar (1984).
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Akaogi M, Akimoto S (1980) High-pressure stability of a dense hydrous magnesian silicate Mg23Si8O42H6 and some geophysical implications. J Geophys Res 85:6944–6948
Akaogi M, Ross NL, McMillan P, Navrotsky A (1984) The Mg2SiO4 polymorphs (olivine, modified spinel, and spinel) — Thermodynamic properties from oxide melt solution calorimetry, phase relations, and models of lattice vibrations. Am Mineral 69:499–512
Akimoto S, Akaogi M (1980) The system Mg2SiO4-MgO-H2O at high pressures and temperatures — Possible hydrous magnesian silicates in the mantle transition zone. Phys Earth Planet Interiors 23:268–275
Akimoto S, Akaogi M (1984) Possible hydrous magnesian silicates in the mantle transition zone. In: Sunagawa I (ed) Materials Science of the Earth's Interior, Terra Pub Tokyo, pp 477–480
Bence AE, Albee AL (1968) Empirical correction factors for the electron microanalysis of silicates and oxides. J Geol 76:382–403
Benimoff AI, Sclar CB (1984) Further characterization of “phase A” in the system MgO-SiO2-H2O. Trans Am Geophys Union 65:308
Farmer VC (1974) The Infrared Spectra of Minerals. Mineral Soc Monogr 4
Horiuchi H, Morimoto N, Yamamoto K, Akimoto S (1979) Crystal structure of 2 Mg2SiO4·3 Mg(OH)2, a new high-pressure structure type. Am Mineral 64:593–598
Iishi K (1978) Lattice dynamics of forsterite. Am Mineral 63:1198–1208
Jeanloz R (1980) Infrared spectra of olivine polymorphs: α, β phase and spinel. Phys Chem Minerals 5:327–341
Paques-Ledent MT, Tarte P (1973) Vibrational studies of olivine-type compounds-I. The i.r. and Raman spectra of the isotopic species of Mg2SiO4. Spectrochim Acta 29A:1007–1016
Ribbe PH, Gibbs GV, Jones NW (1968) Cation and anion substitutions in the humite minerals. Min Mag 36:966–975
Ringwood AE, Major A (1967) High-pressure reconnaissance investigations in the system Mg2SiO4-MgO-H2O. Earth Planet Sci Letters 2:130–133
Servoin JL, Piriou B (1973) Infrared reflectivity and Raman scattering of Mg2SiO4 single crystal. Phys Status Solidi B 55:677–686
Van Valkenburg A (1961) Synthesis of the humites nMg2SiO4. Mg(F, OH)2. J Res Nat Bur Stand 65A:415–428
Yamamoto K, Akimoto S (1974) High-pressure and high-temperature investigations in the system MgO-SiO2-H2O. J Solid State Chem 9:187–195
Yamamoto K, Akimoto S (1977) The system MgO-SiO2-H2O at high pressures and temperatures — Stability field for hydroxyl-chondrodite, hydroxyl-clinohumite and 10 Å-phase. Am J Sci 277:288–312
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Akaogi, M., Akimoto, Si. Infrared spectra of high-pressure hydrous silicates in the system MgO-SiO2-H2O. Phys Chem Minerals 13, 161–164 (1986). https://doi.org/10.1007/BF00308158
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00308158