Ultrahigh-Pressure Melting of a Model Chondritic Mantle and Pyrolite Compositions

  1. Murli H. Manghnani and
  2. Yasuhiko Syono
  1. Eiji Ohtani

Published Online: 21 MAR 2013

DOI: 10.1029/GM039p0087

High-Pressure Research in Mineral Physics: A Volume in Honor of Syun-iti Akimoto

High-Pressure Research in Mineral Physics: A Volume in Honor of Syun-iti Akimoto

How to Cite

Ohtani, E. (1987) Ultrahigh-Pressure Melting of a Model Chondritic Mantle and Pyrolite Compositions, in High-Pressure Research in Mineral Physics: A Volume in Honor of Syun-iti Akimoto (eds M. H. Manghnani and Y. Syono), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM039p0087

Author Information

  1. Department of Earth Sciences, Faculty of Science, Ehime University, Matsuyama 790, Japan

Publication History

  1. Published Online: 21 MAR 2013
  2. Published Print: 1 JAN 1987

ISBN Information

Print ISBN: 9780875900667

Online ISBN: 9781118664124

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Keywords:

  • Mineralogy and Crystal Chemistry;
  • Phase transformations;
  • High Pressure-High Temperature Research

Summary

Melting experiments on chondritic mantle and pyrolite compositions for the five-component system CaO-MgO-FeO-Al2O3-SiO2 were conducted to a pressure of 20 GPa. For the chondritic mantle composition, the liquidus phase changes from olivine to majorite between 12 and 15 GPa. For the pyrolite composition, olivine is the liquidus phase at least up to 15 GPa, whereas both modified spinel and majorite coexist around the liquidus temperature and 20 GPa. The majorite crystals coexisting with the partial melt have CaO/Al2O3 lower than chondritic for the chondritic mantle and pyrolite compositions. The majorite fractionation by partial melting at the base of the upper mantle could generate an ultrabasic magma with CaO/Al2O3 higher than chondritic. Such fractionation in the early stage of terrestrial evolution could have produced the chemical stratification of the mantle composed of a peridotitic upper mantle with high CaO/Al2O3 and a majorite-enriched transition zone with a relatively low CaO/Al2O3.