Examining the tectonic context of sedimentary copper deposits using geological and passive seismic methods

Thesis

The fundamental importance of metals such as copper (Cu), nickel, lithium, and cobalt to electricity transmission and battery technology has seen them become critical components of the energy transition to a Net Zero future. However, the declining effectiveness of mineral exploration programs has led many to predict a global deficit of metals such as Cu in the coming decade. Sedimentary-Cu deposits currently account for a significant amount of the world’s copper production, yet the exploration for new deposits is severely hampered by our limited understanding of the first-order geological processes controlling deposit formation. The purpose of this thesis is to test new technologies and workflows to better understand the formation of sedimentary copper deposits and improve the exploration performance for these deposits. The thesis uses the Kansanshi Copper (Cu) – Gold (Au) mine of the Central African Copperbelt as a natural laboratory for this work. Kansanshi is the third largest copper producer in Africa, with a resource estimate of 982.3 Mt of copper as of December 2023. Herein, I show that novel nodal seismometers (Sercel WiNG nodes) are appropriate for passive seismology at a subregional to regional scale. I found that an experimental network comprised of 30 WiNG nodes was able to reliably image a significant body of source sediments beneath the Kansanshi mine. This supports the importance of local sediment accommodation space to the formation of sediment-Cu deposits, and the suitability of ambient noise tomography as a tool in mineral exploration. I have broadened this perspective through the development of a new workflow for analysing the Pressure (P) – Temperature (T) history of metamorphic rocks. This was integrated with detailed field mapping and structural analysis to provide a new model for the geodynamic and structural evolution of the Kansanshi mine. I conclude that Kansanshi comprises an allochthonous, kyanite-grade (550–620 °C, 7.5–9.5 kbar) metamorphic sheet that was thrust over a Lower Roan depocentre during the later stages of the Lufilian Orogeny, both during and prior to Cu-Au mineralisation. Integrating these diverse geophysical and geological approaches in terms of technology and process has resulted in new insights into the formation of one of the world’s premier sediment-hosted Cu mines. In addition, it has added a new tool to the sedimentary Cu exploration tool kit and insight into the formation of the Central African Copperbelt regionally.

Authors: MacKay-Champion, TC

• DOI: 10.5287/ora-xq9zomqee
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English