Scientific article

Reported supergene sphalerite rims at the Chuquicamata porphyry deposit (northern Chile) revisited: Evidence for a hypogene origin

Publication date2015

Previous studies attributed a supergene origin to sphalerite rimming copper minerals occurring in Chuquicamata in a mineral assemblage including typically chalcocite-digenite (Cu1.85S1.12 and u1.99S1.01), covellite(CuS and Cu1.08S0.92), and sphalerite (up to 1.2 wt % Fe). Microscopic observations on samples from a central and a southern section, completed by scanning electronic microscope (SEM) backscattering electron imaging and electron microprobe analyses, suggest that all sphalerite in Chuquicamata is hypogene. A scenario, backed by observations in each step, that explains the formation of the peculiar “sphalerite rims” is the following: (1) precipitation of chalcopyrite, typical of the early and main hydrothermal stages; (2) precipitation of sphalerite rimming chalcopyrite and in voids and in weakness sites during the late hydrothermal stage; (3) partial or total replacement of chalcopyrite by chalcocite-digenite during the late hydrothermal stage; and (4) formation of lamellar covellite, principally at the expense of chalcopyrite, suggesting increasingly oxidizing and/or acidic conditions. This covellite may be linked to supergene processes and/or to the late hydrothermal stage. The findings of the present work have implications for the position of the lower limit of the supergene enrichment in the eastern-southern part of the deposit, as the sphalerite rims, now interpreted as hypogene, were the only potential supergene sulfide in the eastern vertical section of the southern section.

  • Sphalerite
  • Porphyry
  • Chuquicamata
  • Swiss National Science Foundation - 129988
Citation (ISO format)
PINGET, Marie-Caroline et al. Reported supergene sphalerite rims at the Chuquicamata porphyry deposit (northern Chile) revisited: Evidence for a hypogene origin. In: Economic geology and the bulletin of the Society of Economic Geologists, 2015, vol. 110, n° 1, p. 253–262. doi: 10.2113/econgeo.110.1.253
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Article (Published version)
ISSN of the journal0361-0128

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