Geochronology, Isotope Geochemistry, and Molybdenum Distribution in the Central African Copperbelt: Examples from Chibuluma West, Kamoa, and Kipushi

• Author / Creator

  Bowman, Samuel

• The Chibuluma West, Kamoa, and Kipushi stratiform deposits of the Central African Copperbelt have been evaluated using a series of geochemical techniques to better constrain the timing and origin of these deposits, with relevance to the origin of the Copperbelt as a whole. Petrographic, isotopic (Os, Pb, and O), and Mo distribution analyses have determined four mineralization events, occurring before, during, and after the Lufilian orogeny. A possible preenrichment event occurred throughout deposition of the Sturtian glaciation. The glacier scoured and carried U-rich lithic clats from the basement before depositing the Grand Conglomerate (host rock of Kamoa deposit). Radiogenic lead is likely the cause of apparent diagenetic model lead ages for other deposits throughout the Central African Copperbelt.The second mineralization event occurred during the Lufilian orogeny. The Chibuluma West and Kamoa deposits experienced the majority of ore mineralization ~550 to 540 Ma and ~510 to 480 Ma respectively. The Kamoa deposit is unfolded and unmetamorphosed, allowing the true age of the stratiform mineralization to be placed in the late stage of the Lufilian orogeny. The ores of these deposits were likely sourced from the crust. The third mineralization event occurred after the Lufilian orogeny. The ores of the Kipushi deposit mineralized <430 Ma. A new geothermometric approach, using oxygen diffusion in syn-ore dolomite has been successfully shown to estimate fluid temperatures. The ore fluid for the Kipushi deposit is constrained to temperatures between 350oC to 500oC, and over a time less than or equal to 10 Ma.A fourth and final mineralization event occurred in the Late Paleozoic ~ 330 to 300 Ma at the Kamoa and Kipushi deposits. Some amount of ore must have mineralized at this time, as model Pb ages are equivalent with Re-Os ages from molybdenite. This molybdenite is found in fractures crosscutting Lufilian ore. While this timing is highly unusual, it may reflect a collisional event at the southern margin of the Gondwana supercontinent. This previously unknown mineralization event further complicates the ores of the Central African Copperbelt, and the stratiform ore model as a whole.

• Subjects / Keywords

  • Kamoa
  • Mo mapping
  • Central African Copperbelt
  • Geochemistry
  • Isotope
  • Kipushi
  • Chibuluma West

• Graduation date

  Spring 2019

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-3vct-3e04

• License

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