Hydrothermal alteration of the graphitized organic matter at the Kansanshi Cu (Au-,U-) deposit, Zambia

Abstract

Hydrothermal alteration of greenschist facies metamorposed organic matter in host rocks of the Kansanshi vein-type copper (Au-, U-) deposit produced ¹³C depleted amorphous carbon phase (pyrobitumen) and CO₂≫CH₄ volatile phase. Compared with graphitized organic matter in non-altered rocks, FTIR spectra of amorphous carbon phase in altered rock display significant increase of C=O and C=C vibrations, C-H deformation vibrations and C-O vibrations of ethers. Depletion of hydrothermal carbonates with ¹³C indicates that the interaction between graphitized organic matter and hydrothermal fluids was a major source of carbon in the fluids. A large volume of bleached carbonaceous schists at the Kansanshi deposit suggests that the hydrothermal decomposition of graphitized organic matter to a great extend controlled the redox state of the ore fluids.