Diamond and Graphite in Eclogite Xenoliths from Kimberlite

  1. F.R. Boyd and
  2. Henry O.A. Meyer
  1. Derek N. Robinson

Published Online: 19 MAR 2013

DOI: 10.1029/SP016p0050

The Mantle Sample: Inclusion in Kimberlites and Other Volcanics

The Mantle Sample: Inclusion in Kimberlites and Other Volcanics

How to Cite

Robinson, D. N. (1979) Diamond and Graphite in Eclogite Xenoliths from Kimberlite, 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/SP016p0050

Author Information

  1. Anglo American Research Laboratories, P.O. Box 106, Crown Mines, 2025, Republic of 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:

  • Diamond;
  • Graphite;
  • Kimberlite;
  • Petrogenesis;
  • Xenoliths

Summary

The characteristics of diamond and graphite in a number of diamond- and/or graphite-bearing eclogite xenoliths are described. In most cases of eclogite specimens containing diamond, the proportions of diamond present exceed that in kimberlite by more than a factor of three. The diamonds are similar to those in kimberlite and very small proportions of disaggregated diamond-bearing eclogite can account for much, even all, of the diamond in some kimberlite. Morphological features of diamond and graphite crystals, and spatial relationships between them in diamond-graphite eclogite, indicate that both minerals are primary and favour an igneous origin for the rocks. In one specimen there is evidence that partial resorption and etching of diamond crystals was effected by the liquid from which diamond crystallized, and not by kimberlite. In another specimen, however, kimberlite volatiles were evidently responsible for resorbing and etching diamond. Considering the low density of graphite, graphite-bearing eclogite is unlikely to represent crystal cumulate derived by gravitational settling. At least some of the diamond-graphite eclogite xenoliths are probably samples of abundant, very small bodies of carbon-bearing eclogite. Simple crystallization paths can be inferred for most specimens studied. In one xenolith, however, two generations of diamond are clearly evident and it is apparent that an increase in temperature occurred during crystallization of the rock.