| Summary: | Abstract: Eleven microinclusion-bearing fibrous diamonds from the Fox kimberlite, Ekati mine, Northwest Territories, with either coated or cubic-like morphologies were analyzed for their major and trace element and Sr isotopic compositions. High-density fluid (HDF) microinclusions of saline compositions were found in 9 of the diamonds and silicic compositions in 2 diamonds. Some of the saline diamonds encapsulate also micro-mineral inclusions of their peridotite host rock (olivine, orthopyroxene, Cr-diopside and chromite); the silicic diamonds contain microinclusions of omphacitic clinopyroxene and are related to eclogite host. Both saline and silicic HDFs are enriched in incompatible elements; they have fractionated REE patterns with elevated Ba, U, Th and LREE but depleted Nb, Ta and alkalis (K, Rb, and Cs). The fractionated nature of these patterns are more pronounced in the saline HDFs, which are also characterized with positive Eu- and Sr-anomalies versus no Eu anomaly and negative Sr anomalies in the silicic fluids. 87Sr/86Sri in the saline HDFs are 0.7039-0.7090 compared to 0.7064 and 0.7111 in the two diamonds with silicic fluids. Also provided, the trace element composition of one diamonds from the Diavik mine, Canada.
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