Ultrahigh-Pressure Metamorphic Graphite and Diamond
From the Kokchetav Massif, Northern Kazakhstan
A very interesting occurrence of graphite occurs with diamond in the ultra-high pressure metamorphic rocks of the diamond-bearing garnet-clinopyroxene rocks and clinozoisite gneisses at the Kumdy-Kol and Barchi-Kol microdiamond deposits. The graphite occurs in a variety of morphologies, including well-crystallized tabular or columnar crystals, and spheroidal aggregates sometimes enclosing microdiamonds. Information and images on these pages are provided courtesy of Dr. Andrey Korsakov,
Click on the map for a larger map with geological details.
Scanning electron microscope (SEM) images of a diamond crystal (not visible) completely overgrown by highly crystalline graphite from garnet-clinopyroxene rocks from the Kokchetav massif (for detailed mineralogy and petrology see Korsakov and Hermann 2006). (Click on any image to see a higher resolution image.)
(a) Overall view of graphite coated diamond. (b-c) Enlargement showing a large euhedral graphite crystal connected only by a narrow neck to "main" aggregates.
(d-f) Details of the surface morphology of graphite crystals presented in (b-c).
(g-l) Overall view and details of growth layers on a euhedral graphite crystal from the graphite coating.
REFERENCES:
Andrey V. Korsakov, Karel Theunissen and Larissa V. Smirnova (2004) Intergranular diamonds derived from partial melting
of crustal rocks at ultrahigh-pressure metamorphic conditions. Terra Nova 16, 146-151.
Andrey V. Korsakov and Jörg Hermann (2006) Silicate and carbonate melt inclusions associated with diamonds in deeply subducted carbonate rocks. Earth and Planetary Science Letters 241, 104-118.
A.V. Korsakov, K. Theunissen,
O.A. Kozmenko, and Yu.I. Ovchinnikov (2006) Reaction textures in
clinozoisite gneisses. Russian Geology and Geophysics
[Geologiya i Geofizika]
47(4), 499-512.
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© Copyright Andrey Korsakov and John A. Jaszczak