A Diamond-Graphite Eclogite from the Roberts Victor Mine

  1. F.R. Boyd and
  2. Henry O.A. Meyer
  1. C.J. Hatton and
  2. J.J. Gurney

Published Online: 19 MAR 2013

DOI: 10.1029/SP016p0029

The Mantle Sample: Inclusion in Kimberlites and Other Volcanics

The Mantle Sample: Inclusion in Kimberlites and Other Volcanics

How to Cite

Hatton, C.J. and Gurney, J.J. (1979) A Diamond-Graphite Eclogite from the Roberts Victor Mine, in The Mantle Sample: Inclusion in Kimberlites and Other Volcanics (eds F.R. Boyd and H. O.A. Meyer), American Geophysical Union, Washington, D.C.. doi: 10.1029/SP016p0029

Author Information

  1. Department of Geochemistry, University of Cape Town, Rodenbosch, 7700 South Africa

Publication History

  1. Published Online: 19 MAR 2013
  2. Published Print: 1 JAN 1979

ISBN Information

Print ISBN: 9780875902135

Online ISBN: 9781118664858

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Keywords:

  • Clinopyroxenes compositions;
  • Diamond-graphite eclogite;
  • Roberts victor mine;
  • Silicates formation;
  • Xenolith HRV247

Summary

The coexistence of diamond and graphite in a Roberts Victor eclogite indicate that the eclogite formed under pressure and temperature conditions close to the diamond-graphite reaction curve. The silicates have crystallised over a range of temperature and pressure conditions which transect the diamond-graphite equilibrium curve at 1020 to 1140°C and 42 to 45 kbar. In this pressure-temperature range the carbon-gas (CCO) buffer curve defines oxygen fugacities close to those considered reasonable approximations of the oxygen fugacity of the mantle. Diamond and graphite therefore may have formed by reduction of carbon oxides during cooling of the silicate magma. The eclogite is believed to have formed by the crystallisation of a partial melt produced by disequilibrium melting of garnet lherzolite under volatile-rich conditions.