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Bacteria as Mediators of Copper Sulfide Enrichment During Weathering
1R. H. Sillitoe, 27 West Hill Park, Highgate Village, London N6 6ND, UK. R. L. Folk, Department of Geological Sciences, University of Texas, Austin, TX 78712, USA. N. Saric, Sociedad Minera Pudahuel S. A., Avenida Ricardo Lyon 527, Santiago, Chile.
Abstract:
Supergene chalcocite enrichment during weathering is an economically vital natural process that may lead to severalfold increases in the copper content of sulfide deposits. A scanning electron microscope study of chalcocite (Cu2S) from major enriched copper deposits in northern Chile revealed myriad bacterioform bodies in original growth positions near replacement interfaces with remnant hypogene sulfide grains. These minute (0.03 to 0.2 micrometers) chalcocite bodies are interpreted as fossilized and metallized nannobacteria that promoted the fixation of mobilized copper ions. Bacterial activity may thus be a fundamental factor in supergene enrichment of copper deposits.