Abstract
The Dando-Kwanza concession is situated in the incised highlands of Bié Province in central Angola. An aerial reconnaissance survey conducted in 2005 drew attention to artisanal alluvial mining, in the vicinity of six kimberlite occurrences discovered during colonial times. Exploration commenced in 2007 and the subsequent 3-year work program led to the discovery of 39 new kimberlite occurrences. The concession is underlain by Archean gneisses of the Central Shield Zone of the Angolan Shield, which have been intruded by Paleoproterozoic granitoids at ~1.97 Ga (this study). The basement is overlain by Paleozoic red beds of the West Congolian Inkisi Group which are host to many of the kimberlites. The Lubia cluster kimberlites occur within the northern part of the concession and were emplaced at ~238 Ma, based on zircon U–Pb and mica-in-kelyphite Ar–Ar geochronology. The kimberlites are pipes, some with multiple lobes, with surface areas of up to 16.7 ha. They occur as resedimented volcaniclastic, pyroclastic, and coherent magmatic varieties and have been classified as Group 1 kimberlites. Facies types have been interpreted as crater deposits with narrow hypabyssal feeders and one calcite kimberlite as extrusive lava. Microdiamond sampling of the kimberlites returned low modeled grades and it is postulated that erosion of an enriched and eluviated ferricrete cap on many of the kimberlites may explain the prevalence of alluvial diamonds immediately downstream of the kimberlites. Low diamond grades and the low to moderate interest major element composition of garnets and chromites may be related to perturbation of the SCLM by high-T melt-related processes during Paleoproterozoic times.
An erratum to this chapter can be found at http://dx.doi.org/10.1007/978-81-322-1173-0_20
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Acknowledgments
The authors gratefully acknowledge De Beers and Endiama for permission to publish this data. Barbara Scott-Smith and Roger Mitchell are thanked for useful comments relating to the MK-B kimberlites. Mike Shaw is thanked for discussions on the different gravel types in the area and Gargi Mishra for discussions around the kimberlite petrography. Anton le Roex is thanked for facilitating the whole-rock geochemistry analyses of the MK-A and MK-B kimberlites, which were conducted at University of Cape Town. We thank Herman Grütter, Brooke Clements and an anonymous reviewer for their constructive comments.
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Jelsma, H. et al. (2013). Kimberlites from Central Angola: A Case Study of Exploration Findings. In: Pearson, D., et al. Proceedings of 10th International Kimberlite Conference. Springer, New Delhi. https://doi.org/10.1007/978-81-322-1173-0_12
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DOI: https://doi.org/10.1007/978-81-322-1173-0_12
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