Non-cylindrical parasitic folding and strain partitioning during the Pan-African Lufilian orogeny in the Chambishi-Nkana Basin, Central African Copperbelt

Abstract

Abstract.A structural analysis has been carried out along the southeast margin of the Chambishi-Nkana Basin in the Central African Copperbelt, hosting the world-class 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, 5 characterized by non-cylindrical NW-SE elongated, 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 development of parasitic folds and certain lithofacies assemblages in the Copperbelt Orebody Member, 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 10 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 mineralization and (re−)mobilization in the Copperbelt.