Unravelling the origins of giant ore-bearing olistoliths in Kolwezi, DRC
Following a series of large-scale slope stability issues within Glencore’s K.O.V pit in Kolwezi, DRC, Tect was contracted by Kamoto Copper Company in 2017 to undertake a detailed structural study of the K.O.V and Mashamba East Pits. The aim of the study was to resolve the structural context and geometries of large, mineralized écaille or fragments, hosted by “mega-breccias” and to represent these in fully-constrained, geometrically-realistic, implicit 3D geological models in Leapfrog. These models will be used in downstream analysis, such as geotechnical analysis, slope design, and geohydrology.
The scope of work included structural and lithological pit mapping over the course of 3 years, drillcore review, structural analysis of regional and local, mine-scale features, 3D structural and lithological modelling and Apparent Dip AnalysisTM. Tertiary analysis determines the interaction of modelled lithological contacts, bedding and low-angle structures with design and pushback wireframes, allowing Geotechnical Engineers to better define and constrain Geotechnical design sectors for monitoring and mine planning. As on many other operations that Tect has worked on, an effective structural mapping procedure was established, allowing for quick, accurate face mapping by KCC’s Geotechnical Engineers and Technicians, using digital mapping devices and external GPS receivers. This produces a continuous stream of critical structural data as mining advances and as new faces become available.
Pit mapping reveals soft-sediment deformation features, variable size, geometry and attitudes of mineralized fragments, brittle faulting within fragments, a lack of pervasive shearing/tectonism, discordant sedimentary relationships and a block-in-matrix geometry. These observations largely invalidate previous hypotheses which suggest that the mineralized fragments within the K.O.V. area were formed by halokinesis or as tectonic friction breccias, but rather point toward modified sedimentary mélanges or olistostromes, preserved within a remnant of a tectonic foreland basin (the Kolwezi “Klippe”).
Tect’s involvement with KCC is on-going, and at the time of writing (March 2020), a Geotechnical drilling campaign is underway to update the 3D Structural and Lithological Model, empowering the Geotechnical Department to make informed decisions on risk mitigation and slope design. Future work for K.O.V includes the development of a form surface model that takes into account drillhole data, structural face mapping and downhole macro-structural point data. This will create a series of 3D form surfaces that represent the constantly-varying orientation of bedding within each major mineralized fragment and the manner in which this interacts with current faces and future designs.
An article on the geology of K.O.V. is currently being drafted. This will be focused on the structural characteristics of the deposit and how these relate to the mechanisms responsible for the formation and preservation of the mineralization in K.O.V. Mine and other related deposits within the Kolwezi sub-basin or “klippe”.
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