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The formation of micro diamonds in decompression cracks out of equilibrium controlled by the C:O:H ratio in the kimberlitic melt

Sommer, Holger and Gasharova, Biliana and Regenauer-Lieb, Klaus and Colliston, Wayne and Potgieter, Jessika (2014) The formation of micro diamonds in decompression cracks out of equilibrium controlled by the C:O:H ratio in the kimberlitic melt. International Association of Gondwana Research.

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    Abstract

    Diamonds are supposed to be formed in the diamond window under high-pressure conditions due to the polymorph graphite/diamond phase transition. In this study we present for the first time, that natural diamonds can be formed by C:O:H bearing volatiles during the uplift of the kimberlitic melt in eclogites from the Roberts Victor mine, South Africa. Our results give evidence that the kimberlitic melt acts like a catalyst, and therefore the C:O:H ratio in the kimberlite changes through the uplift of the kimberlite permanently, caused by the formation of hydrous and carbonatitic minerals within the kimberlitic melt. This catalytic process leads to the growth of light carbon bearing molecules and under favorable thermodynamic, stoichiometric and kinetic conditions micro diamonds can be formed, even under lower pressure conditions outside of the diamond window. High-spatial-resolution synchrotron based FT-IR has been used to detect C:O:H-bearing volatiles around planar defect structures in garnet. In micro diamond bearing planar defect structures, a correlation between C:O:H-bearing volatiles could be identified whereas in micro diamond free planar defect structures no correlation of the different C:O:H containing volatiles is visible. The conclusions from our study proves that C:O:H-bearing volatiles, and their distribution pattern around the studied micro cracks, are suggestive of the formation of micro diamonds in natural eclogites.

    Item Type: Other
    Additional Information: This is part of a conference series published by the International Association of Gondwana Research. It is a Book of Abstracts. No Full paper provided.
    Subjects: Q Science > QE Geology
    Divisions: Faculty of Science, Technology and Environment (FSTE) > School of Geography, Earth Science and Environment
    Depositing User: Holger Sommer
    Date Deposited: 20 Oct 2015 14:57
    Last Modified: 26 May 2016 15:35
    URI: http://repository.usp.ac.fj/id/eprint/8503
    UNSPECIFIED

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