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The Juina diamond field, in the 1970–80s, was producing up to 5–6million carats per year from rich placer deposits, but no economic primary deposits had been found in the area. In 2006–2007, Diagem Inc. discovered a group of diamondiferous kimberlitic pipes within the Chapadão Plateau (Chapadão, or Pandrea cluster), at the head of a drainage system which has produced most of the alluvial diamonds...
We thank Mitchell and Tappe for giving us the opportunity to discuss the nature of kimberlite magmas. We agree with Mitchell and Tappe about the importance of mineralogy, but the mineralogy of interstitial phases in kimberlites can shed little light on the origin of kimberlite magmas. Our use of cation units enables the interpretation of kimberlite whole-rock compositions in terms of the stoichiometry...
The origin of kimberlites and volatile-rich alkaline ultramafic magmas such as aillikites has been a matter of considerable scientific interest and the recent paper by Francis and Patterson (Francis and Patterson, 2009. Kimberlites and Aillikites as probes of the continental lithospheric mantle. Lithos 109, 72–80) attempts to summarize advances in this research field. They introduce new major element...
Although diamonds of eclogitic paragenesis are commonly encountered in the productions of many Southern Africa kimberlites, the nature and evolution of the protolith to eclogitic diamonds are still poorly understood. There is some evidence that these protoliths (and possibly also the diamonds) may be related to subduction of oceanic crust, although this is not a universally accepted view. In order...
The ~380Ma Nyurbinskaya kimberlite pipe, Yakutia, Siberia, sampled a highly-diamondiferous and unusual mantle xenolith population dominated by eclogites. New in-situ major- and trace-element data for garnets previously analyzed for oxygen isotope compositions show that Group A eclogitic garnets have Mg# >68 and are LREE-depleted. Group B and Group C eclogitic garnets cover a range of Mg#, and are...
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