Basin analysis of the Katangan Basin of Zambia: subsidence mechanisms, dynamic stratigraphy, and mineral systems

Thesis

The Neoproterozoic Katangan basin of Central Africa represents the largest sediment-hosted copper province on Earth, recording ∼300 Myr of sedimentation. This work applies a basin analysis approach to understanding the basin’s evolution in Zambia, combining facies analysis, sequence stratigraphy, and subsidence analysis.

The Katangan basin shows two phases of rifting and thermal subsidence, punctuated by two major glacial events. The Lower Roan Group comprises the proximally deposited terrestrial syn-rift fill of the initial amagmatic rift, reaching decompacted thicknesses of ∼2.6 km in Solwezi. The overlying Upper Roan Group shows a sharp transition to carbonate-dominated facies and evaporite successions deposited in an epicontinental sea with extensive paralic zones as the basin transitioned from fault-controlled to predominantly thermally controlled subsidence.

The Mwashia Group represents a second, magmatic, phase of rifting between ∼765 and ∼735 Ma. It is expressed in the Zambian Copperbelt predominantly as distal facies, starved of coarse sediment, recording the basin deepening and expanding beyond the initial Lower Roan rift. The base of the Nguba is traditionally demarkated by diamictites at its base and was accommodated via post-rift thermal subsidence. The Kundelungu is demarkated at its base by a regionally correlatable sea level lowstand and glacial diamictites. It represents an initially quiescent tectonic regime prior to flexure and basin inversion.

Backstripped subsidence profiles support a diachronous rift origin for the basin. The Lower Roan central rift zone is interpreted to have been situated south of the Domes region in Zambia, with crustal stretching exceeding 50%. It likely accommodated > 8 km Katangan stratigraphy prior to basin inversion during the Lufilian orogeny.

Facies analysis, sequence stratigraphy, and quantitative subsidence analysis can inform understanding of the Katangan’s mineral systems, emphasising the importance of rapid retrogradational successions in forming potential mineralisation sites and possible diachroneity of mineralised units. When combined, they can form the foundation of quantitative estimates of mineralisation potential.

Authors: Purkiss, M

• DOI: 10.5287/ora-zog1wdbpn
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: facies analysis; subsidence analysis; neoproterozoic; Katangan Basin; stratigraphy; mineral systems
• Subjects: Mineral exploration; Sequence stratigraphy; Subsidence analysis; Geology, Economic; Basin analysis; Sedimentology