Sulphide Re-Os geochronology links orogenesis salt and Cu-Co ores in the Central African Copperbelt

摘要

The origin of giant, sedimentary rock-hosted copper-cobalt (Cu-Co) provinces remains contentious, in part due to the lack of precise and reliable ages for mineralisation. As such, no consensus has been reached on the genetic model for ore formation, and the relationships between tectonism, palaeo-fluid circulation and mineralisation. Here, we link the timing of Cu-Co mineralisation in the Central African Copperbelt to compressional tectonics during the Lufilian Orogeny by using new ca. 609–473 Ma ages given by rhenium-osmium (Re-Os) isotope data for individual Cu-Co sulphides (carrolite and bornite) from the Cu-Co Kamoto deposit. The initial Os isotope composition of carrolite is compatible with the leaching of Os and Cu(-Co) from Mesoproterozoic Cu sulphide deposits hosted in fertile basement. In contrast, the ca. 473 Ma Cu-Au mineralisation stage, which is coeval with late- to post-compressional deformation, may be a distal expression of fluid flow and heat transfer caused by magmatic intrusions in the core of the collisional orogen. The Re-Os ages support a model for mineralisation driven by evaporite dissolution and percolation of large volumes of dense brines in the Katangan Basin during the Lufilian Orogeny.