Abstract
Abstract. A structural analysis has been carried out along the south-east margin of the Chambishi–Nkana Basin in the Central African Copperbelt, hosting the world-class copper and cobalt (Cu–Co) Nkana orebody. The geometrically complex structural architecture is interpreted to have been generated during a single NE–SW-oriented compressional event, clearly linked to the Pan-African Lufilian orogeny. This progressive deformation resulted primarily in asymmetric multiscale parasitic fold assemblages, characterised by non-cylindrical NW–SE-oriented periclinal folds that strongly interfere laterally, leading to fold linkage and bifurcation. The vergence and amplitude of these folds consistently reflect their position along an inclined limb of a NW-plunging megascale first-order fold. A clear relation is observed between the intensity of parasitic folding and the degree of shale content in the Copperbelt Orebody Member (COM), which hosts most of the ore. Differences in fold amplitude, wavelength and shape are explained by changes in mechanical stratigraphy caused by lateral lithofacies variation in ore-bearing horizons. In addition, strong differences in strain partitioning occur within the deforming basin, which is interpreted to be in part controlled by changes in mechanical anisotropy in the layered rock package. This work provides an essential backdrop to understand the influence of the Lufilian orogeny on metal mineralisation and (re-)mobilisation in the Copperbelt.
Highlights
The Central African Copperbelt is the largest and highestgrade sediment-hosted copper- and cobalt-producing metallogenic province in the world (Fig. 1)
Metallogenesis in the Central African Copperbelt is generally seen as a multistage and often deposit-specific process with at least some of the following: diagenetic mineralisation pulses are followed by multiple remobilisation stages related to basin inversion and compressional deformation, and by later supergene enrichment (e.g. Cailteux et al, 2005; Selley et al, 2005; Dewaele et al, 2006; Haest and Muchez, 2011; Hitzman et al, 2012)
The regional structural analysis on the south-east margin of the Chambishi–Nkana Basin has shown that compressional deformation is characterised by parasitic non-cylindrical NW–SE elongate periclinal fold geometries that strongly interfere laterally, leading to fold linking and bifurcation of folds
Summary
The Central African Copperbelt is the largest and highestgrade sediment-hosted copper- and cobalt-producing metallogenic province in the world (Fig. 1). It hosts over 80 deposits with more than 152 million metric tonnes of contained Cu (Zientek et al, 2010) or approximately 200 million metric tonnes according to Hitzman et al (2012), as well as the largest Co reserves in the world ( > 60 %). Metallogenesis in the Central African Copperbelt is generally seen as a multistage and often deposit-specific process with at least some of the following: diagenetic mineralisation pulses are followed by multiple remobilisation stages (including potential new mineralisation) related to basin inversion and compressional deformation, and by later supergene enrichment
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