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Titel OH and CO2 diffusion profiles in garnets around two dimensional defect structures from eclogitic xenoliths from the Rovic diamond mine, South Africa
VerfasserIn Jessika Potgieter, Holger Sommer, Klaus Regenauer-Lieb, Biliana Gasharova
Konferenz EGU General Assembly 2010
Medientyp Artikel
Sprache Englisch
Digitales Dokument PDF
Erschienen In: GRA - Volume 12 (2010)
Datensatznummer 250040816
 
Zusammenfassung
The mechanism of kimberlite eruptions plays a significant role in diamond exploration. The composition of the kimberlitic melt is a major physical aspect in understanding the eruption dynamics of kimberlites and therein diamond resorption due to changes in fO2. In the studied eclogites, water and CO2 is commonly dissolved in nominally water free minerals (NAMS) as OH and CO2 around defect structures. The enrichment of volatiles is caused by mantle metasomatism and affected the outermost rims of the studied eclogites. The eruption of the kimberlite causes water to partition prefentially into the kimberlitic melt due to the higher solubility of water in the melt compared to NAMS. The concentration of OH and CO2 around defect structures in garnets can thus be used, to quantify the composition of the kimberlitic melt. For the first time high resolution FT-IR based synchrotron measurements of OH and CO2 concentrations in eclogitic garnets from the Rovic Diamond Mine in South Africa is presented. Hydrogen and CO2 profiles, has been measured towards totally embedded microcracks in the garnet crystals. These measurements show a strong variation in OH and CO2 concentrations, which demonstrate that the amount of water and carbondioxide stored in diamond bearing layers has been underestimated for a long time due to the loss of water and carbondioxide during the uplift of the kimberlite.